{ "version": "v1", "source": "https://craftquantities.com", "licence": "CC BY 4.0", "licenceUrl": "https://creativecommons.org/licenses/by/4.0/", "attribution": "Craft Quantities — craftquantities.com", "documentation": "https://craftquantities.com/api/", "versioning": "Fields are added, never removed or repurposed, within a version. A breaking change becomes /api/v2/ and v1 keeps being built.", "description": "Construction terminology across the United States, Canada, the United Kingdom and Australia. One record per CONCEPT, not per word. Every market name states how close the equivalence is — identical, close, false-friend (the same word meaning different things) or absent — and anything other than identical carries a note saying what is not being claimed.", "count": 153, "concepts": [ { "slug": "plasterboard", "concept": "Plasterboard / drywall", "family": "materials", "definition": "A rigid board with a gypsum core faced in paper, fixed to studs or furring to form a flat internal wall or ceiling surface, then jointed and finished.", "url": "https://craftquantities.com/glossary/plasterboard/", "names": [ { "market": "US", "term": "drywall", "alsoCalled": [ "gypsum board", "wallboard", "sheetrock" ], "exactness": "identical", "note": "\"Sheetrock\" is a brand name used generically." }, { "market": "CA", "term": "drywall", "alsoCalled": [ "gypsum board" ], "exactness": "identical", "note": null }, { "market": "UK", "term": "plasterboard", "alsoCalled": [ "gypsum board" ], "exactness": "identical", "note": null }, { "market": "AU", "term": "plasterboard", "alsoCalled": [ "gyprock" ], "exactness": "identical", "note": "\"Gyprock\" is a brand name used generically in Australia." } ], "standards": [ { "market": "US", "standard": "ASTM C1396", "covers": "The board itself — core, facing, dimensions and tolerances." }, { "market": "UK", "standard": "BS EN 520", "covers": "Plasterboard definitions, requirements and test methods." } ], "calculators": [ { "slug": "drywall-calculator", "json": "https://craftquantities.com/api/v1/calculators/drywall-calculator.json" }, { "slug": "drywall-joint-compound-calculator", "json": "https://craftquantities.com/api/v1/calculators/drywall-joint-compound-calculator.json" }, { "slug": "drywall-corner-bead-calculator", "json": "https://craftquantities.com/api/v1/calculators/drywall-corner-bead-calculator.json" } ], "confusions": [ { "question": "Is plasterboard the same as drywall?", "answer": "Yes — the same product under two words: a gypsum core faced in paper, fixed to a frame and jointed. British and Australian usage is plasterboard, American and Canadian usage is drywall, and gypsum board is the formal term in both. What differs is not the product but the finishing tradition around it. North American practice normally tapes and fills the joints and leaves the paper face as the substrate for decoration, while British practice may either tape and fill the same way or skim the whole surface with a thin plaster coat — which produces a different surface, a different trade and a different quantity of material. So a specification saying drywall and one saying plasterboard describe the same board, and may not describe the same finished wall." }, { "question": "What is sheetrock?", "answer": "A brand of gypsum board, used generically in the United States much as gyprock is in Australia. It is not a different product or a grade, and a specification calling for sheetrock is calling for gypsum board. It matters when reading a quotation or a schedule, because the brand name carries no information about the board's type, thickness, edge profile or fire and moisture performance — all of which are specified separately — so a supplier offering another manufacturer's equivalent board is supplying the specified product rather than a substitute. Check the board type and thickness in the specification, not the name in the quote." }, { "question": "Do board sizes match across markets?", "answer": "No, and the difference is dimensional rather than terminological. North American boards are made in imperial widths and lengths — four feet wide, in lengths chosen to suit standard ceiling heights and stud spacing at sixteen or twenty-four inches. British and Australian boards are metric, commonly 1200 mm wide to suit stud centres at 400 or 600 mm, in metric lengths. A 1200 mm board is a little under four feet, so the two are close enough to look interchangeable on a drawing and are not: the sheet count for an area differs, the joints land in different places, and the framing centres the board was designed for are a different module." } ], "related": [ "render", "skirting", "timber", "skim", "dry-lining" ] }, { "slug": "timber", "concept": "Timber / lumber", "family": "materials", "definition": "Sawn wood used structurally or for carpentry, as distinct from a manufactured wood panel such as plywood or OSB.", "url": "https://craftquantities.com/glossary/timber/", "names": [ { "market": "US", "term": "lumber", "alsoCalled": [], "exactness": "close", "note": "In American usage \"timber\" tends to mean standing trees or very large sections, not ordinary sawn stock." }, { "market": "CA", "term": "lumber", "alsoCalled": [], "exactness": "close", "note": "As the United States, lumber is the everyday word for sawn stock while timber means very large sections or the standing resource." }, { "market": "UK", "term": "timber", "alsoCalled": [], "exactness": "identical", "note": null }, { "market": "AU", "term": "timber", "alsoCalled": [], "exactness": "identical", "note": null } ], "standards": [ { "market": "US", "standard": "NDS", "covers": "Design values and methods for wood construction." }, { "market": "UK", "standard": "BS EN 1995 (Eurocode 5)", "covers": "Design of timber structures." }, { "market": "AU", "standard": "AS 1720", "covers": "Timber structures design." } ], "calculators": [ { "slug": "lumber-dimensional-size-calculator", "json": "https://craftquantities.com/api/v1/calculators/lumber-dimensional-size-calculator.json" }, { "slug": "board-foot-lumber-cost-calculator", "json": "https://craftquantities.com/api/v1/calculators/board-foot-lumber-cost-calculator.json" }, { "slug": "wood-load-duration-factor-calculator", "json": "https://craftquantities.com/api/v1/calculators/wood-load-duration-factor-calculator.json" }, { "slug": "timber-notch-reduction-calculator", "json": "https://craftquantities.com/api/v1/calculators/timber-notch-reduction-calculator.json" }, { "slug": "timber-shear-connector-count-calculator", "json": "https://craftquantities.com/api/v1/calculators/timber-shear-connector-count-calculator.json" } ], "confusions": [ { "question": "Is a 2x4 the same everywhere?", "answer": "No, and this is the entry that changes a quantity rather than a word. A North American 2x4 is a NOMINAL size: the piece is named for its dimensions before drying and planing, and the finished piece is smaller than that in both directions by an amount fixed in the grading rules. British and Australian sawn timber is specified in millimetres, and the figure quoted may be the sawn size or the finished planed size depending on how it is sold — a different convention, not a translation of the same one. So there is no metric equivalent of a 2x4, only a nearest available size; substituting one for the other changes the section's depth, and depth is what governs a joist's stiffness." }, { "question": "What does timber mean in American usage?", "answer": "Usually either standing trees or very large sawn sections, rather than the ordinary sawn stock a British or Australian reader means by the word. In North America the everyday trade term for sawn structural wood is lumber, and \"timber\" is reserved for heavy sections — the sizes used in post-and-beam and heavy timber framing — and for the forestry sense of the standing resource. So an American specification for timber is usually describing something larger and more specific than a British one using the same word, and it is worth confirming which is meant rather than assuming, because the two readings imply very different members and very different prices." }, { "question": "Are grading and strength classes comparable?", "answer": "Not directly, and this is the second place the words hide a number. North American lumber is graded to rules published by grading agencies, with design values assigned per species group and grade. European and British practice assigns a STRENGTH CLASS — a C or D designation — which bundles the design properties into one label independent of species, so the same class can be met by several species and grades. Australian practice uses its own stress grades. A specification calling for one system's designation cannot be met by picking the nearest-looking label in another: the mapping is a design exercise, and the properties that matter differ between the systems rather than merely being renamed." } ], "related": [ "plasterboard", "nominal-size", "osb", "arris", "hardwood-softwood" ] }, { "slug": "cladding", "concept": "Cladding / siding", "family": "envelope", "definition": "The outermost weather-facing layer of an external wall, fixed over the structure and any sheathing, carrying no load other than its own weight and the wind on it.", "url": "https://craftquantities.com/glossary/cladding/", "names": [ { "market": "US", "term": "siding", "alsoCalled": [], "exactness": "close", "note": "\"Siding\" in North America usually implies boards or panels. \"Cladding\" is understood there but is not the everyday trade word." }, { "market": "CA", "term": "siding", "alsoCalled": [], "exactness": "close", "note": "As the United States, siding means boards or panels; cladding is understood but is not the everyday trade word for the whole family." }, { "market": "UK", "term": "cladding", "alsoCalled": [ "weatherboarding" ], "exactness": "close", "note": "Cladding is BROADER than siding: it covers brick slips, rainscreen panels and metal systems as well as boards." }, { "market": "AU", "term": "cladding", "alsoCalled": [ "weatherboard" ], "exactness": "close", "note": "As the UK. \"Weatherboard\" specifically means overlapping timber boards, not the whole family." } ], "standards": [ { "market": "UK", "standard": "BS 8414", "covers": "Fire performance of external cladding systems, tested as a complete system rather than by material." }, { "market": "AU", "standard": "NCC Volume One", "covers": "External wall requirements including combustibility provisions." } ], "calculators": [ { "slug": "siding-calculator", "json": "https://craftquantities.com/api/v1/calculators/siding-calculator.json" }, { "slug": "board-and-batten-siding-calculator", "json": "https://craftquantities.com/api/v1/calculators/board-and-batten-siding-calculator.json" }, { "slug": "siding-starter-strip-calculator", "json": "https://craftquantities.com/api/v1/calculators/siding-starter-strip-calculator.json" }, { "slug": "lap-siding-fastener-schedule-calculator", "json": "https://craftquantities.com/api/v1/calculators/lap-siding-fastener-schedule-calculator.json" }, { "slug": "fluid-applied-wrb-coverage-calculator", "json": "https://craftquantities.com/api/v1/calculators/fluid-applied-wrb-coverage-calculator.json" } ], "confusions": [ { "question": "Is cladding the same as siding?", "answer": "Not quite, and the difference is breadth rather than product. Siding, in American and Canadian usage, normally means boards or panels applied to a wall — vinyl, fibre cement, timber, engineered wood. Cladding, in British and Australian usage, covers all of that and also brick slips, rainscreen panel systems, metal and composite panels, and stone facings. So every siding is cladding, and a good deal of cladding is not siding. Reading a British specification calling for cladding as though it meant lap boards will miss the system it is actually describing, and the quantities, the fixings and the support behind it are all different." }, { "question": "Why does cladding come up in fire regulation?", "answer": "Because the outer skin of a tall building is a path fire can travel up the outside, and because the SYSTEM rather than the material determines whether it does. Regulation in several markets tightened substantially after fatal fires, and the approach that emerged is to test a complete assembly — the panel, its core, the insulation behind it, the cavity and the cavity barriers — rather than to certify a material in isolation, because a panel that performs acceptably alone can behave very differently over a ventilated cavity with combustible insulation behind it. The practical consequence when reading across markets is that a product approved in one jurisdiction is not thereby approved in another: what was approved was a system, not a board." }, { "question": "What is a rainscreen, and is it a kind of cladding?", "answer": "Yes, and it is a strategy rather than a material. A rainscreen cladding is hung clear of the wall on rails or brackets with a ventilated and drained cavity behind it, and the outer skin is deliberately NOT relied on to be watertight — it takes most of the weather, and whatever gets past it drains down the cavity and out at the base. The actual weather line is an air and water barrier on the wall behind. That is a different arrangement from a face-sealed system, where the outer surface and its joints are the barrier, and it is why the cavity, its depth, its ventilation openings and its cavity barriers are the parts a rainscreen specification spends its words on." } ], "related": [ "render", "curtain-wall" ] }, { "slug": "gutter", "concept": "Gutter / eavestrough", "family": "envelope", "definition": "The channel at the eaves that collects water running off the roof and carries it to an outlet and a vertical pipe.", "url": "https://craftquantities.com/glossary/gutter/", "names": [ { "market": "US", "term": "gutter", "alsoCalled": [], "exactness": "identical", "note": null }, { "market": "CA", "term": "gutter", "alsoCalled": [ "eavestrough" ], "exactness": "identical", "note": "\"Gutter\" is used across Canada as well; eavestrough is the regional word." }, { "market": "UK", "term": "gutter", "alsoCalled": [ "rainwater gutter" ], "exactness": "identical", "note": null }, { "market": "AU", "term": "gutter", "alsoCalled": [ "spouting" ], "exactness": "identical", "note": "\"Spouting\" is more common in New Zealand than Australia but is understood in both." } ], "standards": [ { "market": "UK", "standard": "BS EN 12056-3", "covers": "Roof drainage design — gutter and outlet sizing." }, { "market": "US", "standard": "IPC / UPC", "covers": "Storm drainage provisions including roof drainage sizing." } ], "calculators": [ { "slug": "gutter-calculator", "json": "https://craftquantities.com/api/v1/calculators/gutter-calculator.json" }, { "slug": "gutter-hanger-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/gutter-hanger-spacing-calculator.json" }, { "slug": "gutter-guard-calculator", "json": "https://craftquantities.com/api/v1/calculators/gutter-guard-calculator.json" } ], "confusions": [ { "question": "What is the vertical pipe called, and does that differ too?", "answer": "Yes, and it catches people more often than the gutter itself. The pipe taking water from the gutter to the ground is a downpipe in British and Australian usage, a downspout in American and Canadian usage, and a rainwater pipe in formal British specification. A \"leader\" is the American plumbing-code word for the same pipe. All four describe one component. The related word that does NOT map is \"gutter\" in the highway sense — the channel at the edge of a carriageway beside the kerb — which is a completely different element of a completely different trade, and is the one meant in kerb and gutter work on a road." }, { "question": "Why is gutter sizing a calculation rather than a standard size?", "answer": "Because the flow depends on the roof, the rainfall intensity and the outlets, none of which is constant. The water a gutter must carry is the plan area draining into it multiplied by a design rainfall intensity for that location and return period, and the capacity available depends on the gutter's cross-section, its fall, and crucially the number and position of outlets — a long gutter with one outlet at one end carries far less than the same gutter with outlets at both. That is why roof drainage is designed rather than picked from a catalogue, and why a gutter perfectly adequate in one climate overflows in another beneath an identical roof." }, { "question": "Is a box gutter the same thing?", "answer": "It is a gutter, and it is a considerably more demanding one, which is why it has its own word in all four markets. A box gutter runs within the roof — in a valley, behind a parapet, or between two roof planes — rather than at an eaves edge, so an overflow does not spill harmlessly outside the building but into it. Because of that, box gutters are designed with a larger margin, with overflow provision as an explicit requirement, and with attention to the outlet's capacity rather than just the channel's. The failure mode is different too: an eaves gutter that blocks drips down a wall, while a box gutter that blocks floods a ceiling." } ], "related": [ "soffit", "flashing", "downpipe" ] }, { "slug": "render", "concept": "Render / stucco", "family": "finishes", "definition": "A wet-applied coating on an external masonry or lathed wall, built up in coats and finished to a texture, giving weather resistance and appearance.", "url": "https://craftquantities.com/glossary/render/", "names": [ { "market": "US", "term": "stucco", "alsoCalled": [ "cement plaster" ], "exactness": "close", "note": "American stucco is specifically a Portland-cement plaster, a narrower family than British render." }, { "market": "CA", "term": "stucco", "alsoCalled": [], "exactness": "close", "note": "As the United States, stucco means a Portland-cement plaster specifically, which is narrower than the render family a British or Australian specification means." }, { "market": "UK", "term": "render", "alsoCalled": [ "cement render", "monocouche" ], "exactness": "close", "note": "Render covers cement, lime and polymer systems — a broader family than American stucco." }, { "market": "AU", "term": "render", "alsoCalled": [ "cement render", "acrylic render" ], "exactness": "close", "note": "As the UK, render covers cement, lime and polymer systems — so it is a broader family than American stucco, and the systems are not interchangeable." } ], "standards": [ { "market": "US", "standard": "ASTM C926", "covers": "Application of Portland cement-based plaster." }, { "market": "UK", "standard": "BS EN 13914-1", "covers": "Design, preparation and application of external rendering." } ], "calculators": [ { "slug": "stucco-calculator", "json": "https://craftquantities.com/api/v1/calculators/stucco-calculator.json" }, { "slug": "stucco-3coat-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/stucco-3coat-volume-calculator.json" }, { "slug": "stucco-lath-calculator", "json": "https://craftquantities.com/api/v1/calculators/stucco-lath-calculator.json" }, { "slug": "eifs-finish-coat-coverage-calculator", "json": "https://craftquantities.com/api/v1/calculators/eifs-finish-coat-coverage-calculator.json" }, { "slug": "block-filler-coverage-calculator", "json": "https://craftquantities.com/api/v1/calculators/block-filler-coverage-calculator.json" }, { "slug": "stucco-control-joint-calculator", "json": "https://craftquantities.com/api/v1/calculators/stucco-control-joint-calculator.json" } ], "confusions": [ { "question": "Is render the same as stucco?", "answer": "Closely related rather than identical, and flattening the two loses something that matters. American stucco is a Portland-cement plaster, with its composition and application governed as such. British and Australian render is a broader family: cement renders, lime renders, and proprietary polymer or acrylic systems, each with different vapour permeability, different movement tolerance and different substrates they suit. Substituting one for the other without checking the specification can put an impermeable cement coat on a wall that needed a breathable lime one — which traps moisture in the masonry instead of letting it out, and is a common cause of damage to older solid-wall buildings." }, { "question": "Why do the base coat and the lath matter more than the finish?", "answer": "Because the finish is what is seen and the base is what fails. A rendered or stuccoed wall is a system: a substrate, a means of attachment, one or more base coats carrying the strength and the reinforcement, and a finish coat carrying the appearance. Where the wall is not solid masonry, a metal lath provides the key, and the lath's fixing and laps are what stop the render coming away in sheets. The other detail with the same weight is the base of the wall — a weep screed or bell-cast bead that lets water which gets behind the coating escape, and stops the render standing in contact with the ground. Failures usually trace to one of those two rather than to the mix." }, { "question": "What is monocouche, and is there an American equivalent?", "answer": "Monocouche is a through-coloured, factory-batched render applied in a single pass — literally one coat, though it is normally applied in two passes worked together — which finishes the wall without a separate decorative coat. It is common in Britain and continental Europe and the word is used directly. The nearest American equivalent is a one-coat stucco system, which is a proprietary product family doing broadly the same job, though the products and their approvals are not interchangeable. The point of both is the same: fewer passes, no painting, and the colour in the material rather than on it — with the corresponding disadvantage that a repair is visible in a way a painted finish is not." } ], "related": [ "plasterboard", "cladding", "screed" ] }, { "slug": "skirting", "concept": "Skirting board / baseboard", "family": "finishes", "definition": "The trim run along the base of an internal wall where it meets the floor, covering the junction and protecting the wall surface.", "url": "https://craftquantities.com/glossary/skirting/", "names": [ { "market": "US", "term": "baseboard", "alsoCalled": [ "base trim", "base molding" ], "exactness": "false-friend", "note": "\"Baseboard\" alone means this trim, but \"baseboard heater\" is a heating appliance in the same position — a different thing entirely." }, { "market": "CA", "term": "baseboard", "alsoCalled": [], "exactness": "false-friend", "note": "Same collision as the United States: a baseboard heater is an appliance, not trim." }, { "market": "UK", "term": "skirting board", "alsoCalled": [ "skirting" ], "exactness": "identical", "note": null }, { "market": "AU", "term": "skirting board", "alsoCalled": [ "skirting" ], "exactness": "identical", "note": null } ], "standards": [], "calculators": [ { "slug": "baseboard-trim-calculator", "json": "https://craftquantities.com/api/v1/calculators/baseboard-trim-calculator.json" } ], "confusions": [ { "question": "Is a baseboard heater a baseboard?", "answer": "No, and it is the most consequential collision in this pair. In North America, \"baseboard\" alone means the trim at the foot of a wall, but a \"baseboard heater\" is an electric or hydronic heating element in a low enclosure running along that same position — an appliance, sized in output and in length, with clearances and a circuit behind it. The two share a word and a location and nothing else. A British or Australian reader meeting \"baseboard\" in an American specification should establish which is meant before pricing anything: one is a length of moulded trim, the other is a heating system with an electrical load and a design temperature behind it." }, { "question": "How is skirting measured and ordered?", "answer": "By the running length around the room's perimeter, less the door openings, plus an allowance for cutting and for mitres. The allowance matters more than it looks: skirting is supplied in fixed lengths, so a wall slightly longer than the stock length needs two pieces and a joint, and the offcut from each length is usually too short to be useful elsewhere. That makes the practical quantity a function of the room's dimensions against the supplier's lengths rather than the perimeter alone. External corners consume more than internal ones because both pieces are mitred, and a room with several returns can need noticeably more material than its perimeter suggests." }, { "question": "Why are internal corners coped rather than mitred?", "answer": "Because rooms are not square, and a mitre shows it. A mitred internal corner relies on the two walls meeting at exactly ninety degrees; when they do not — and in practice they rarely do — the mitre opens as a visible wedge that gets worse as the timber moves. A coped joint instead runs the first piece into the corner square, then scribes the second to the profile of the first, so the second piece sits against the face of the first and the joint closes regardless of the corner's actual angle. It also tolerates seasonal movement better, because shrinkage slides the profile along the face rather than opening a gap." } ], "related": [ "cornice", "plasterboard", "architrave", "dado-rail", "plinth" ] }, { "slug": "worktop", "concept": "Worktop / countertop / benchtop", "family": "finishes", "definition": "The horizontal working surface fitted over base units in a kitchen, utility room or laboratory.", "url": "https://craftquantities.com/glossary/worktop/", "names": [ { "market": "US", "term": "countertop", "alsoCalled": [ "counter" ], "exactness": "identical", "note": null }, { "market": "CA", "term": "countertop", "alsoCalled": [ "counter" ], "exactness": "identical", "note": null }, { "market": "UK", "term": "worktop", "alsoCalled": [ "work surface" ], "exactness": "identical", "note": null }, { "market": "AU", "term": "benchtop", "alsoCalled": [ "bench" ], "exactness": "false-friend", "note": "\"Bench\" elsewhere on site means a cut step in a slope, or a level reference — not a kitchen surface." } ], "standards": [], "calculators": [ { "slug": "countertop-calculator", "json": "https://craftquantities.com/api/v1/calculators/countertop-calculator.json" } ], "confusions": [ { "question": "Does \"bench\" mean the same thing in Australia?", "answer": "In a kitchen, yes — the Australian word for the working surface is benchtop, and \"the bench\" is that surface. Elsewhere on a building site the word keeps its ordinary meanings, so context settles it: a bench in earthworks is a horizontal step cut into a slope to stabilise it or to give plant a working platform, and a benchmark is a fixed level reference. Neither is the kitchen sense. The risk is negligible on a drawing and real in a written scope of works, where an unqualified \"bench\" can be read three ways — which is why \"benchtop\" is the term worth using in a document that will be read across markets." }, { "question": "How is a worktop measured for ordering?", "answer": "By the run length rather than the area, because it is supplied in lengths of a fixed depth and the depth is rarely the variable. The quantity is the sum of the runs, plus the allowance for joints, plus whatever the cut-outs cost — a sink and a hob are cut from the material rather than saved from it, so they add nothing back. Corners are where the arithmetic stops being linear: a mitred or masons-mitre corner consumes extra length from both pieces, and an L or U shaped kitchen can need noticeably more material than the sum of its wall lengths. Overhangs at a breakfast bar, and the end panels, are the two items most often left out." }, { "question": "Does the material change what the word means?", "answer": "No, but it changes what is being quoted, and that catches people more often than the word does. Worktop, countertop and benchtop all name the same position regardless of what it is made of — laminate, solid timber, engineered stone, natural stone, stainless steel — but the supply and fixing are completely different between them. A laminate top is supplied in lengths and cut on site; a stone top is templated after the units are fitted and delivered as finished pieces with the cut-outs already made, which is a separate visit and a longer programme. So a quotation for one material is not comparable to a quotation for another even at the same price per length, because what is included differs." } ], "related": [] }, { "slug": "cornice", "concept": "Cornice / coving / crown molding", "family": "finishes", "definition": "A moulded section run along the junction of wall and ceiling, concealing the joint and finishing the room.", "url": "https://craftquantities.com/glossary/cornice/", "names": [ { "market": "US", "term": "crown molding", "alsoCalled": [], "exactness": "close", "note": "Spelled \"molding\"; the British and Australian spelling is \"moulding\". \"Cornice\" in American usage more often means an external feature." }, { "market": "CA", "term": "crown moulding", "alsoCalled": [], "exactness": "close", "note": "Canadian usage generally keeps the British spelling, but the American meaning: the internal wall-to-ceiling trim rather than an external facade feature." }, { "market": "UK", "term": "cornice", "alsoCalled": [ "coving" ], "exactness": "close", "note": "Coving is the plain concave section; cornice usually implies a profiled or decorative one." }, { "market": "AU", "term": "cornice", "alsoCalled": [ "coving", "cove cornice" ], "exactness": "close", "note": "As the UK, and plain cove cornice is the common default in plasterboard construction." } ], "standards": [], "calculators": [ { "slug": "crown-molding-calculator", "json": "https://craftquantities.com/api/v1/calculators/crown-molding-calculator.json" } ], "confusions": [ { "question": "What is the difference between coving and cornice?", "answer": "Profile rather than position. Both run along the wall-to-ceiling junction; coving is a plain concave section, effectively a simple curve between the two surfaces, while a cornice usually implies a profiled or decorative section with mouldings worked into it. In practice the words are used loosely and often interchangeably, and Australian plasterboard practice calls the standard plain section a cove cornice, which uses both words for one thing. Where the distinction earns its keep is in pricing and fixing: a heavy decorative cornice is a different installation from a light cove, and in an older building the existing cornice may be fibrous plaster, which is repaired rather than replaced." }, { "question": "Why does the mitre matter so much on this trim?", "answer": "Because the section sits at an angle to both surfaces it meets, so its corners are compound rather than simple. A crown or cornice section leans away from the wall, which means the cut at a corner has to account for both the corner's angle in plan and the section's spring angle — and a mitre-saw setting correct for flat trim leaves a gap on crown. The two practical approaches are to cut the piece nested against the fence at its spring angle, which preserves the simple settings, or to cope the internal corners so one piece is scribed to the profile of the other, which absorbs the out-of-square corners every real room has." }, { "question": "Does cornice mean something different outside?", "answer": "Yes, and it is the reason the American word for the internal trim is different. In classical architecture and in American usage generally, a cornice is the projecting moulded feature at the top of an external wall, beneath the eaves — a facade element rather than a room finish. British usage applies the word to both, with context distinguishing them, which is why an American reader can find a British specification for \"cornice\" in a bedroom slightly surprising. Where a document is read across markets, \"crown molding\" or \"cove cornice\" for the internal trim and \"eaves cornice\" for the external feature removes the ambiguity entirely." } ], "related": [ "skirting" ] }, { "slug": "screed", "concept": "Screed", "family": "finishes", "definition": "In British and Australian usage, the levelling layer laid over a structural floor to receive the finish. In American usage the word more often means the tool or the act of striking a surface off level, or a fixed edge used to do it.", "url": "https://craftquantities.com/glossary/screed/", "names": [ { "market": "UK", "term": "screed", "alsoCalled": [ "floor screed", "sand-cement screed" ], "exactness": "false-friend", "note": "The LAYER: a levelling course over the slab, of a stated thickness, receiving the floor finish." }, { "market": "AU", "term": "screed", "alsoCalled": [ "floor screed" ], "exactness": "false-friend", "note": "As the UK, the LAYER: a levelling course over the slab. The American sense — the tool or the act of striking off — is not what an Australian specification means." }, { "market": "US", "term": "screed", "alsoCalled": [ "screed rail", "screed board" ], "exactness": "false-friend", "note": "The TOOL or the ACT: striking concrete off to level, or the rail that guides it. The layer is an underlayment or a topping." }, { "market": "CA", "term": "screed", "alsoCalled": [ "underlayment", "topping" ], "exactness": "false-friend", "note": "As the United States for the tool sense; the layer is normally an underlayment or a topping." } ], "standards": [ { "market": "UK", "standard": "BS 8204-1", "covers": "Concrete bases and cement sand levelling screeds — materials and workmanship." }, { "market": "US", "standard": "ACI 302.1R", "covers": "Concrete floor and slab construction, including toppings and finishing." } ], "calculators": [ { "slug": "heated-screed-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/heated-screed-volume-calculator.json" }, { "slug": "self-leveling-underlayment-calculator", "json": "https://craftquantities.com/api/v1/calculators/self-leveling-underlayment-calculator.json" }, { "slug": "screed-cubic-yards-to-tons-calculator", "json": "https://craftquantities.com/api/v1/calculators/screed-cubic-yards-to-tons-calculator.json" } ], "confusions": [ { "question": "Does screed mean a layer or a tool?", "answer": "Both, in different markets, and it is one of the cleanest false friends in construction English. In Britain and Australia a screed is the levelling LAYER over a structural floor — a sand-cement or proprietary material laid to a stated thickness to bring the floor to level and to receive the finish — and it is priced by area and thickness. In the United States the word more often refers to the ACT of striking a surface off to level, or to the TOOL or rail that guides it; the layer a British reader means is an underlayment or a topping. So an American specification saying \"screed the slab\" is describing an operation, and a British one saying \"75 mm screed\" is describing material to be delivered." }, { "question": "What is a weep screed, then?", "answer": "The American sense: a formed metal edge trim, not a layer. A weep screed is fitted at the base of a stuccoed or rendered wall, providing a stopped edge for the coating and openings through which water that gets behind it can escape. It is a strip of profiled metal a few inches deep, and it has nothing whatever to do with a floor screed. The same applies to a casing bead or a plaster screed rail used to gauge thickness. This site's own catalog holds both senses — a screed volume calculator and a weep screed calculator — which is why the glossary lists each concept's calculators explicitly rather than matching on the word." }, { "question": "Why does screed thickness matter so much?", "answer": "Because it governs both strength and drying time, and the two pull in opposite directions. Too thin and a bonded or unbonded screed cracks and breaks up under load, particularly at doorways and along its edges; too thick and it takes considerably longer to dry to the moisture content a floor finish will tolerate, which is often the item that delays handover. Whether the screed is bonded to the slab, laid unbonded on a membrane, or floating on insulation changes the minimum thickness substantially, as does whether it carries underfloor heating pipes. So a thickness copied from another job without knowing which of those it was is a guess with two failure modes." } ], "related": [ "render", "cement", "self-levelling-compound", "movement-joint", "underfloor-heating" ] }, { "slug": "skip", "concept": "Skip / dumpster", "family": "site", "definition": "The open container waste is loaded into on site and removed in, hired by size and by period.", "url": "https://craftquantities.com/glossary/skip/", "names": [ { "market": "US", "term": "dumpster", "alsoCalled": [ "roll-off" ], "exactness": "identical", "note": "\"Dumpster\" is a brand name used generically; a large site container delivered on a hooklift is a roll-off." }, { "market": "CA", "term": "dumpster", "alsoCalled": [ "bin", "roll-off" ], "exactness": "identical", "note": null }, { "market": "UK", "term": "skip", "alsoCalled": [], "exactness": "identical", "note": null }, { "market": "AU", "term": "skip", "alsoCalled": [ "skip bin" ], "exactness": "identical", "note": null } ], "standards": [], "calculators": [ { "slug": "skip-and-dumpster-size-calculator", "json": "https://craftquantities.com/api/v1/calculators/skip-and-dumpster-size-calculator.json" }, { "slug": "dumpster-size-selector-calculator", "json": "https://craftquantities.com/api/v1/calculators/dumpster-size-selector-calculator.json" }, { "slug": "dumpster-rental-cost-calculator", "json": "https://craftquantities.com/api/v1/calculators/dumpster-rental-cost-calculator.json" } ], "confusions": [ { "question": "Are skip sizes and dumpster sizes comparable?", "answer": "Only through their volume, and even that is quoted differently. British skips are commonly described by a nominal capacity in cubic yards and by familiar names — a builder's skip, a midi, a maxi — while American containers are quoted in cubic yards as roll-off sizes and Australian skip bins in cubic metres. Converting between them is arithmetic, but the comparison is still not like for like, because what limits a container in practice is usually WEIGHT rather than volume: heavy waste such as soil, rubble or plaster reaches the permitted load long before the container is full, which is why suppliers restrict those materials to smaller containers or to separate hires." }, { "question": "Why does mixing waste cost more than separating it?", "answer": "Because a mixed container has to be sorted after collection, and the sorting is priced into the hire. Where the waste stream is separated on site — clean rubble in one, timber in another, plasterboard kept out of both — each stream has a lower disposal cost and some carry a recovery value, while a single mixed container is charged at the rate for whatever is hardest to deal with in it. Plasterboard is the usual reason a rate jumps, because gypsum is restricted from mixing with biodegradable waste in several jurisdictions and is handled separately. The trade-off is space and discipline on site against the disposal rate, which is why it is decided at planning rather than at the skip." }, { "question": "What is the difference between a skip and a roll-off?", "answer": "How it is loaded onto the lorry, which sets the practical size range. A skip is lifted by chains onto a tipper-style vehicle and is the smaller family, with the familiar sloped-end shape. A roll-off — the large rectangular container common on North American sites — is winched or hooked onto a flat bed and rolled off again, which allows a much longer and larger container than chain lifting can manage. The consequence for anyone comparing quotes across markets is that the size ranges overlap only partly: the biggest skips are around the smallest roll-offs, and the container sizes above that have no skip equivalent at all." } ], "related": [ "scaffold", "snagging", "asbestos", "bulking" ] }, { "slug": "reinforcement", "concept": "Reinforcement / rebar", "family": "structure", "definition": "Steel bars or fabric cast into concrete to carry the tension the concrete cannot, placed to a schedule stating each bar's size, shape, position and cover.", "url": "https://craftquantities.com/glossary/reinforcement/", "names": [ { "market": "US", "term": "rebar", "alsoCalled": [ "reinforcing steel", "reinforcing bar" ], "exactness": "identical", "note": null }, { "market": "CA", "term": "rebar", "alsoCalled": [ "reinforcing steel" ], "exactness": "identical", "note": null }, { "market": "UK", "term": "reinforcement", "alsoCalled": [ "rebar", "reinforcement bar" ], "exactness": "identical", "note": "\"Rebar\" is understood and used in Britain too; \"reinforcement\" is the formal term, and the one BS 8666 schedules are written in." }, { "market": "AU", "term": "reinforcement", "alsoCalled": [ "reo", "rebar" ], "exactness": "identical", "note": "\"Reo\" is common Australian site shorthand, including \"reo mesh\" for fabric." } ], "standards": [ { "market": "US", "standard": "ACI 318", "covers": "Structural concrete design including reinforcement detailing." }, { "market": "UK", "standard": "BS 8666", "covers": "Scheduling, dimensioning, bending and cutting of steel reinforcement — the schedule's own format and shape codes." }, { "market": "AU", "standard": "AS 3600", "covers": "Concrete structures design." } ], "calculators": [ { "slug": "rebar-calculator", "json": "https://craftquantities.com/api/v1/calculators/rebar-calculator.json" }, { "slug": "rebar-lap-splice-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/rebar-lap-splice-length-calculator.json" }, { "slug": "rebar-development-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/rebar-development-length-calculator.json" }, { "slug": "slab-rebar-combined-mass-calculator", "json": "https://craftquantities.com/api/v1/calculators/slab-rebar-combined-mass-calculator.json" }, { "slug": "seismic-reinforcement-ratio-calculator", "json": "https://craftquantities.com/api/v1/calculators/seismic-reinforcement-ratio-calculator.json" }, { "slug": "rebar-weight-calculator", "json": "https://craftquantities.com/api/v1/calculators/rebar-weight-calculator.json" } ], "confusions": [ { "question": "Are bar sizes the same across markets?", "answer": "No, and the numbering conventions are not even the same kind of number. Imperial bar designations in the United States are based on eighths of an inch of nominal diameter, so a #4 bar is roughly half an inch. Metric designations in Britain, Australia and most of the world state the nominal diameter in millimetres directly, so a 12 mm bar is 12 mm. There is also a soft-metric American designation that restates the imperial sizes in millimetres, which is a third set of labels for the same physical bars. A substitution between systems is therefore a design decision about area and spacing rather than a lookup, and the bar shape codes in a schedule are equally market-specific." }, { "question": "What is a bar schedule, and why is its format a standard?", "answer": "It is the document telling a fabricator exactly what to make: every bar's mark, size, shape code, dimensions, quantity and location. The format is standardised because the shape codes are a shared language between designer, fabricator and steel fixer — a code identifies a bending configuration with its dimensions given in a defined order, and a misread code produces bars of the right length and the wrong shape. Britain's is BS 8666, which is why a British schedule looks unfamiliar to a reader from another market even when every dimension on it is legible: the shape codes are the part that does not translate, and reading them as if they were another system's is how a whole delivery goes wrong." }, { "question": "Is mesh called the same thing everywhere?", "answer": "No. The welded sheet of bars used in slabs is welded wire reinforcement or welded wire fabric in the United States and Canada, mesh or fabric in Britain — where the standard designations run A, B and C series by wire size and spacing — and reo mesh in Australian site usage. The designations are market-specific in the same way bar sizes are, so a British A-series designation has no direct American equivalent and vice versa. The other thing that differs is how it is supplied: sheets in some markets, rolls in others, which changes the lap arrangement, the waste and the handling on site rather than the design." } ], "related": [ "ton", "rsj", "footing" ] }, { "slug": "ton", "concept": "Ton / tonne", "family": "measurement", "definition": "A unit of mass used for bulk materials — aggregate, asphalt, soil, steel. Three different quantities share the word, and which one is meant depends on the market and sometimes on the trade.", "url": "https://craftquantities.com/glossary/ton/", "names": [ { "market": "US", "term": "ton", "alsoCalled": [ "short ton", "net ton" ], "exactness": "false-friend", "note": "An unqualified American ton is the SHORT ton — 2,000 pounds — and it is the lightest of the three." }, { "market": "CA", "term": "tonne", "alsoCalled": [ "metric ton", "ton" ], "exactness": "false-friend", "note": "Canada is metric, so \"tonne\" is the metric tonne — but American suppliers and older documents still use short tons, so the word alone is not sufficient." }, { "market": "UK", "term": "tonne", "alsoCalled": [ "metric tonne", "long ton" ], "exactness": "false-friend", "note": "Modern British practice is the metric tonne — 1,000 kilograms. The historic imperial \"long ton\" of 2,240 pounds survives in older documents and in some shipping contexts." }, { "market": "AU", "term": "tonne", "alsoCalled": [ "metric tonne" ], "exactness": "identical", "note": "Australia is metric throughout; the tonne is unambiguous there." } ], "standards": [ { "market": "INTL", "standard": "SI", "covers": "The tonne is accepted for use with SI as 1,000 kilograms exactly." } ], "calculators": [ { "slug": "tons-to-tonnes-calculator", "json": "https://craftquantities.com/api/v1/calculators/tons-to-tonnes-calculator.json" }, { "slug": "tonnes-to-tons-calculator", "json": "https://craftquantities.com/api/v1/calculators/tonnes-to-tons-calculator.json" }, { "slug": "asphalt-tons-to-cubic-yards-calculator", "json": "https://craftquantities.com/api/v1/calculators/asphalt-tons-to-cubic-yards-calculator.json" }, { "slug": "tons-btu-kw-conversion-calculator", "json": "https://craftquantities.com/api/v1/calculators/tons-btu-kw-conversion-calculator.json" } ], "confusions": [ { "question": "How different are a ton and a tonne?", "answer": "Enough to matter on any delivery, and the three values sit close enough together to look like rounding. The American short ton is 2,000 pounds. The metric tonne is 1,000 kilograms, which is about ten per cent heavier than a short ton. The historic British long ton is 2,240 pounds, heavier again, and it is the one most likely to appear without warning in an older specification. A quantity quoted as \"tons\" and supplied as tonnes is under-ordered by roughly a tenth; the reverse over-orders by the same. On a bulk material priced by mass, that is a real error in both the quantity and the invoice, and it is invisible in the arithmetic because the number itself was right." }, { "question": "Why is a ton of refrigeration not a mass at all?", "answer": "Because it is a rate of cooling that happens to be named after one. A ton of refrigeration is defined from the heat required to melt a ton of ice in a day, which is how the unit got its name in the era of ice-based cooling, and it has been a power unit ever since. So an air conditioner described as a three-ton unit weighs nothing like three tons and is being described by its cooling capacity. The two senses share a word and an origin, but one is a rate of heat flow and the other a mass, and they appear in adjacent trades on the same job — which is why HVAC documents normally say \"tons\" for capacity while the same site's aggregate deliveries are in tons of mass." }, { "question": "Why are bulk materials sold by mass rather than volume?", "answer": "Because mass is what a weighbridge can verify and volume is not. A lorry-load of aggregate or asphalt can be weighed exactly, while its volume depends on how it is heaped, how it has settled and how much moisture it carries — so the ticket is written in mass and the site converts to the volume it needs. That conversion is where the density comes in, and density varies with the material, its grading and its moisture content, which is why cubic-yards-to-tons conversions are material-specific rather than generic. It is also why an order placed in volume and delivered in mass needs the density stated somewhere, or the two parties are agreeing on different quantities." } ], "related": [ "gallon", "reinforcement" ] }, { "slug": "gallon", "concept": "Gallon", "family": "measurement", "definition": "A unit of liquid volume. The US gallon and the imperial gallon are different quantities, and the word alone does not say which is meant.", "url": "https://craftquantities.com/glossary/gallon/", "names": [ { "market": "US", "term": "gallon", "alsoCalled": [ "US gallon" ], "exactness": "false-friend", "note": "The US liquid gallon, defined as 231 cubic inches — about four fifths of an imperial gallon." }, { "market": "CA", "term": "litre", "alsoCalled": [ "imperial gallon" ], "exactness": "absent", "note": "Canada is metric: fuel and liquids are sold in litres. The imperial gallon survives in older documents and in some recreational contexts." }, { "market": "UK", "term": "litre", "alsoCalled": [ "imperial gallon" ], "exactness": "absent", "note": "Trade is metric. The imperial gallon — about 4.55 litres — persists in fuel economy figures and in older specifications." }, { "market": "AU", "term": "litre", "alsoCalled": [], "exactness": "absent", "note": "Fully metric; the gallon is not used in Australian trade at all." } ], "standards": [ { "market": "INTL", "standard": "SI", "covers": "The litre is the accepted metric unit of liquid volume; the gallon is not an SI unit." } ], "calculators": [ { "slug": "liters-to-us-gallons-calculator", "json": "https://craftquantities.com/api/v1/calculators/liters-to-us-gallons-calculator.json" }, { "slug": "imperial-gallons-to-liters-calculator", "json": "https://craftquantities.com/api/v1/calculators/imperial-gallons-to-liters-calculator.json" }, { "slug": "cubic-feet-to-gallons-calculator", "json": "https://craftquantities.com/api/v1/calculators/cubic-feet-to-gallons-calculator.json" } ], "confusions": [ { "question": "How much bigger is an imperial gallon?", "answer": "About a fifth, which is more than enough to matter and small enough to pass unnoticed. The imperial gallon is roughly 4.55 litres and the US gallon roughly 3.79 litres, so an imperial gallon is about twenty per cent larger. Paint, sealant, adhesive and fuel are all sold in gallons somewhere, and a coverage rate quoted per gallon in one convention and applied in the other is wrong by that fifth in the direction that matters — under-ordering when an American rate is applied to imperial gallons, over-ordering the other way. The word gives no warning. Any figure taken from a foreign product datasheet is worth converting to litres before it is used." }, { "question": "Does the difference affect coverage rates?", "answer": "Directly, and it is the commonest way this catches somebody out. Paint and coating datasheets quote a coverage — area per unit of product — and the unit is a gallon in North American literature and a litre almost everywhere else. Taking a coverage in square feet per US gallon and applying it to imperial gallons over-estimates how far the product goes by about twenty per cent, which on a large job is the difference between finishing and a second order at a different batch number. The safe practice is to convert the datasheet's coverage into area per litre before doing any arithmetic with it, and to record which convention the original figure came from." }, { "question": "Are fluid ounces the same?", "answer": "No, and confusingly they differ in the opposite direction to the gallons. An imperial gallon contains 160 imperial fluid ounces and a US gallon contains 128 US fluid ounces, so although the imperial gallon is the larger container, the imperial fluid OUNCE is slightly smaller than the US one. That means neither the gallon nor the ounce can be converted by assuming the other is fixed. On site this matters mostly for admixtures, additives and small-quantity products dosed by fluid ounce per unit of mix — where the dosage is small, the tolerance is narrow and the error is invisible until the material behaves unexpectedly." } ], "related": [ "ton" ] }, { "slug": "first-floor", "concept": "First floor / ground floor", "family": "measurement", "definition": "How the storeys of a building are numbered from the entrance level upward — a convention that differs by market, so the same label denotes different levels.", "url": "https://craftquantities.com/glossary/first-floor/", "names": [ { "market": "US", "term": "first floor", "alsoCalled": [ "ground floor", "level 1" ], "exactness": "false-friend", "note": "The first floor IS the entrance level. The storey above it is the second floor." }, { "market": "CA", "term": "first floor", "alsoCalled": [ "ground floor", "main floor" ], "exactness": "false-friend", "note": "As the United States, though \"ground floor\" and \"main floor\" are both common for the entrance level." }, { "market": "UK", "term": "ground floor", "alsoCalled": [ "level 0" ], "exactness": "false-friend", "note": "The entrance level is the GROUND floor; the first floor is one storey above it." }, { "market": "AU", "term": "ground floor", "alsoCalled": [ "level 0" ], "exactness": "false-friend", "note": "As the UK, the entrance level is the ground floor and the first floor is one storey above it — so an Australian first floor is an American second floor." } ], "standards": [], "calculators": [ { "slug": "stair-calculator", "json": "https://craftquantities.com/api/v1/calculators/stair-calculator.json" } ], "confusions": [ { "question": "Which level is the first floor?", "answer": "It depends on the market, and the two conventions are offset by exactly one storey. In the United States and Canada the first floor is the entrance level, so first and ground mean the same thing and the storey above is the second. In Britain, Australia and most of Europe the entrance level is the ground floor and the first floor is one above it, so the British first floor is the American second. The offset persists all the way up, which means a document that names levels rather than numbering them from a datum can misdirect a delivery, an inspection or an installation by one storey without anything in it looking wrong." }, { "question": "How do you write a level unambiguously?", "answer": "By referring to a datum rather than a name. Drawings resolve this with a level in metres or feet relative to a stated datum — a site datum, a benchmark, or finished floor level of a named storey — which is unambiguous in any market because it is a measurement rather than a label. Where names are unavoidable, spelling out \"the entrance level\" or \"one storey above entrance level\" removes the ambiguity that \"first floor\" carries. Building information models and level schedules usually carry both, a name and a datum, and it is worth checking that a document's names and its datums agree before working from either." }, { "question": "Does the mezzanine or basement numbering differ too?", "answer": "Yes, and below ground there is less agreement than above it. Basements are numbered downward in both conventions, but the labels vary — B1, LG, lower ground, level -1 — and a building on a slope can legitimately have two entrance levels, each called ground by the people who use that entrance. Mezzanines are the other ragged case: an intermediate level between two storeys may be numbered as its own level, given a letter, or not numbered at all, which shifts everything above it if the numbering is sequential. Lift call buttons are a notorious instance, since they follow the building's own scheme rather than any market convention." } ], "related": [] }, { "slug": "cement", "concept": "Cement vs concrete", "family": "materials", "definition": "Cement is the BINDER — a fine powder that reacts with water to form a paste that hardens. Concrete is the finished material: cement, water, sand and aggregate. Cement is an ingredient of concrete, in the way flour is an ingredient of bread.", "url": "https://craftquantities.com/glossary/cement/", "names": [ { "market": "US", "term": "cement", "alsoCalled": [ "Portland cement", "concrete (colloquially)" ], "exactness": "false-friend", "note": "In trade use, cement is the binder only. In everyday speech it is routinely used for concrete — a cement drive, a cement floor — which is the error this page exists for." }, { "market": "UK", "term": "cement", "alsoCalled": [ "Portland cement", "OPC" ], "exactness": "false-friend", "note": "Identical to American trade usage, and the same everyday slippage: a concrete path is called a cement path by people who are not laying it." }, { "market": "AU", "term": "cement", "alsoCalled": [ "Portland cement" ], "exactness": "false-friend", "note": "As the UK and the US — the trade meaning is the binder, and the colloquial use for the finished material is just as common." }, { "market": "CA", "term": "cement", "alsoCalled": [ "Portland cement" ], "exactness": "false-friend", "note": "As the United States. The distinction is a trade one everywhere and a colloquial confusion everywhere, rather than a difference between markets." } ], "standards": [ { "market": "US", "standard": "ASTM C150", "covers": "Portland cement — the binder's composition and types." }, { "market": "UK", "standard": "BS EN 197-1", "covers": "Composition, specifications and conformity criteria for common cements." }, { "market": "US", "standard": "ACI 318", "covers": "Structural concrete — the finished material's design." } ], "calculators": [ { "slug": "concrete-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-calculator.json" }, { "slug": "concrete-mix-ratio-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-mix-ratio-calculator.json" }, { "slug": "aci-211-water-cement-ratio-calculator", "json": "https://craftquantities.com/api/v1/calculators/aci-211-water-cement-ratio-calculator.json" }, { "slug": "scm-replacement-calculator", "json": "https://craftquantities.com/api/v1/calculators/scm-replacement-calculator.json" }, { "slug": "trial-batch-yield-adjustment-calculator", "json": "https://craftquantities.com/api/v1/calculators/trial-batch-yield-adjustment-calculator.json" } ], "confusions": [ { "question": "What is the actual difference between cement and concrete?", "answer": "Cement is one ingredient; concrete is the product. Cement is a fine powder, manufactured by burning limestone with other materials and grinding the result, which reacts chemically with water — it hydrates rather than dries — to form a paste that hardens and binds. Concrete is that paste plus sand and coarse aggregate, in proportions chosen for the strength, workability and durability required. A cubic metre of concrete contains a comparatively small proportion of cement by mass, and most of what is in it is stone and sand. So ordering cement when concrete is meant orders a fraction of the material, and the words are not interchangeable on any document that will be priced or delivered from." }, { "question": "Does it matter if I say cement when I mean concrete?", "answer": "In conversation, rarely. On anything that turns into an order, a specification or a claim, considerably. A supplier quoting for cement is quoting for bagged binder; a supplier quoting for concrete is quoting for a delivered mix with a specified strength, slump, aggregate size and exposure class. A specification calling for a cement floor tells a contractor almost nothing about what to lay, and a defect report describing cracked cement makes it impossible to tell whether the complaint is about a concrete slab, a screed or a mortar joint. The other reason to keep the distinction is that cement content is itself a specified quantity — mixes are described partly by how much binder they contain." }, { "question": "What about mortar, grout and screed?", "answer": "All cement-based, all different materials, and all frequently called cement by the same slippage. Mortar is cement, sand and usually lime, without coarse aggregate, used to bed and joint masonry. Grout is a fluid mix used to fill voids — the cores of blockwork, the gap under a baseplate, the joints between tiles — and is proportioned to flow rather than to be worked. Screed is a levelling layer over a floor, in British and Australian usage, laid comparatively dry and compacted rather than poured. Each has its own specification, its own strength criteria and its own failure modes, so describing any of them as cement loses the information that decides what should be delivered." } ], "related": [ "screed", "mortar-designation", "sand", "slump", "lime", "grout" ] }, { "slug": "consumer-unit", "concept": "Consumer unit / breaker panel", "family": "services", "definition": "The enclosure where a building's incoming supply is divided into final circuits, each with its own overcurrent protection, and where the earthing and any residual-current protection are arranged.", "url": "https://craftquantities.com/glossary/consumer-unit/", "names": [ { "market": "UK", "term": "consumer unit", "alsoCalled": [ "CU", "fuse board", "distribution board" ], "exactness": "close", "note": "\"Consumer unit\" is the domestic enclosure specifically; \"distribution board\" is the broader term used for commercial and industrial installations." }, { "market": "US", "term": "panelboard", "alsoCalled": [ "breaker panel", "load center", "service panel" ], "exactness": "close", "note": "\"Load center\" is the residential product and \"panelboard\" the commercial one, so the two American words split the same way the British pair does." }, { "market": "CA", "term": "panelboard", "alsoCalled": [ "breaker panel", "load centre" ], "exactness": "close", "note": "As the United States for the product names, though the governing code and the earthing arrangements are Canadian and differ in detail." }, { "market": "AU", "term": "switchboard", "alsoCalled": [ "distribution board", "DB" ], "exactness": "close", "note": "\"Switchboard\" covers the enclosure and its devices, and is used for domestic and commercial alike rather than splitting the way the British and American terms do." } ], "standards": [ { "market": "UK", "standard": "BS 7671", "covers": "Requirements for electrical installations — the IET Wiring Regulations." }, { "market": "US", "standard": "NFPA 70 (NEC)", "covers": "National Electrical Code — panelboard and overcurrent requirements." }, { "market": "AU", "standard": "AS/NZS 3000", "covers": "Electrical installations — the Wiring Rules." } ], "calculators": [ { "slug": "electrical-panel-load-calculator", "json": "https://craftquantities.com/api/v1/calculators/electrical-panel-load-calculator.json" }, { "slug": "breaker-size-calculator", "json": "https://craftquantities.com/api/v1/calculators/breaker-size-calculator.json" }, { "slug": "grounding-conductor-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/grounding-conductor-sizing-calculator.json" }, { "slug": "service-panel-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/service-panel-sizing-calculator.json" }, { "slug": "electrical-load-calculator", "json": "https://craftquantities.com/api/v1/calculators/electrical-load-calculator.json" }, { "slug": "electrical-working-clearance-calculator", "json": "https://craftquantities.com/api/v1/calculators/electrical-working-clearance-calculator.json" } ], "confusions": [ { "question": "Is an RCD the same as a GFCI?", "answer": "Close in purpose and different in threshold and in where it sits. Both detect an imbalance between the current flowing out and the current returning — the signature of current leaking to earth, possibly through a person — and disconnect. British and Australian practice calls the device an RCD, commonly fits it at the consumer unit to protect groups of circuits or, increasingly, per circuit as an RCBO combining it with overcurrent protection. American practice calls it a GFCI, most familiarly built into a socket outlet in a wet location or into a breaker, and the trip threshold for personal protection differs from the RCD's typical figure. So the words map, the function maps, and the ratings and the installation conventions do not — which is why a device cannot simply be substituted across a specification." }, { "question": "What is an AFCI, and does Britain have one?", "answer": "An arc-fault circuit interrupter detects the electrical signature of an arcing fault — a loose connection, a damaged cable, a pierced conductor — which can generate enough heat to start a fire while drawing too little current to trip an overcurrent device and causing no earth leakage for a residual-current device to see. It is a distinct protection from both, required in American practice for many circuit types. The British and European equivalent is the arc fault detection device, recognised in the wiring regulations and recommended rather than universally mandated. So the concept exists in both, under different names, with different scope — and a specification calling for AFCI protection is calling for a device that is not the default in a British consumer unit." }, { "question": "Why do the earthing arrangements differ so much?", "answer": "Because the supply systems differ, and the protective arrangement follows from how the supply is earthed rather than from a preference. British practice classifies installations by earthing system — whether the earth comes with the supply cable, is combined with the neutral, or is provided by an electrode at the property — and the choice of protective device, the bonding of services and the acceptable earth loop impedance all follow from that classification. American and Canadian practice arranges the service grounding and bonding differently again, and Australian practice differently once more. The practical consequence is that the earthing section of a foreign specification cannot be read across even when every device name translates, because it is describing a different supply." } ], "related": [ "rcd", "ring-final-circuit" ] }, { "slug": "dpc", "concept": "Damp-proof course / membrane", "family": "envelope", "definition": "A layer built into a wall or under a floor to stop liquid water rising through the construction by capillary action. It is not the same component as a vapour control layer, which resists water VAPOUR moving by diffusion.", "url": "https://craftquantities.com/glossary/dpc/", "names": [ { "market": "UK", "term": "damp-proof course (DPC)", "alsoCalled": [ "damp-proof membrane (DPM)" ], "exactness": "false-friend", "note": "DPC is the strip in a wall, DPM the sheet under a floor. Both resist LIQUID rising by capillarity — neither is a vapour control layer, and British practice names that separately." }, { "market": "AU", "term": "damp-proof course", "alsoCalled": [ "DPC", "vapour barrier (under slab)" ], "exactness": "false-friend", "note": "As the UK for the wall component. The under-slab sheet is commonly called a vapour barrier in Australian practice even though its main job is liquid and capillary break — the naming, not the function, differs." }, { "market": "US", "term": "capillary break", "alsoCalled": [ "vapor barrier", "vapor retarder", "under-slab membrane" ], "exactness": "false-friend", "note": "American practice has no everyday equivalent of DPC in a wall, and \"vapor barrier\" names a component defined by its PERMEANCE rather than by stopping rising liquid — so the words map but the specifications do not." }, { "market": "CA", "term": "vapour barrier", "alsoCalled": [ "air barrier", "capillary break" ], "exactness": "false-friend", "note": "Canadian codes distinguish air barrier, vapour barrier and capillary break as three separate functions, which is a finer division than DPC/DPM and does not line up one-to-one with it." } ], "standards": [ { "market": "UK", "standard": "BS 8215", "covers": "Design and installation of damp-proof courses in masonry." }, { "market": "US", "standard": "ASTM E1745", "covers": "Plastic water vapor retarders used in contact with soil under concrete slabs." } ], "calculators": [ { "slug": "vapor-barrier-calculator", "json": "https://craftquantities.com/api/v1/calculators/vapor-barrier-calculator.json" }, { "slug": "vapor-barrier-dewpoint-calculator", "json": "https://craftquantities.com/api/v1/calculators/vapor-barrier-dewpoint-calculator.json" } ], "confusions": [ { "question": "Is a damp-proof course the same as a vapour barrier?", "answer": "No, and treating them as the same is one of the more expensive translation errors in building. A damp-proof course resists LIQUID water rising through masonry by capillary action — water climbing through the pores of brick and mortar from the ground — and it works by being impermeable and continuous in a horizontal plane near the base of a wall. A vapour barrier or vapour retarder resists water VAPOUR moving by diffusion through an assembly, and it is specified by its permeance and by its position relative to the insulation and the dew point. A material can do one and not the other, and putting a vapour barrier in the plane where a DPC belongs, or vice versa, solves neither problem." }, { "question": "What does a specification mean by DPM?", "answer": "The sheet beneath a ground-bearing floor slab, as distinct from the strip in a wall. In British usage a damp-proof membrane is laid under or within a floor construction to stop moisture rising from the ground into the slab and the finish above it, and it is lapped and sealed to the wall's damp-proof course so that the two form one continuous barrier. That continuity is the detail that matters and the one most often missed: a perfect DPM and a perfect DPC with no lap between them leaves a path at the junction. American practice covers the same function with an under-slab membrane or capillary break, specified to a vapour transmission standard rather than to a damp-proofing one." }, { "question": "Why does British practice have a DPC at all?", "answer": "Because of the building stock and the wall construction the word grew up around. Solid and cavity masonry walls built directly off the ground will wick moisture upward through mortar and brick unless the path is interrupted, and in a climate with persistently wet ground that rise is visible as damp staining, salt deposits and decayed plaster a metre or so up the wall. A horizontal impermeable course near the base interrupts it. North American light-frame construction sits on a foundation wall with the timber held clear of the ground and detailed differently, so the problem presents differently and the vocabulary developed around vapour and air control instead. Neither tradition is missing the concept; they divide it differently." } ], "related": [ "cavity-wall", "tanking", "cill", "dpm", "coping" ] }, { "slug": "hardcore", "concept": "Sub-base / hardcore", "family": "site", "definition": "The compacted granular layer between the subgrade and the surfacing, which spreads load into the ground, provides a working platform and drains. Its designations are market-specific product specifications rather than generic descriptions.", "url": "https://craftquantities.com/glossary/hardcore/", "names": [ { "market": "UK", "term": "sub-base", "alsoCalled": [ "hardcore", "MOT Type 1", "Type 1" ], "exactness": "close", "note": "\"MOT Type 1\" is a specific graded crushed rock to a published grading envelope; \"hardcore\" is the older and looser word, historically including broken brick and demolition arisings." }, { "market": "US", "term": "aggregate base", "alsoCalled": [ "crusher run", "base course", "road base" ], "exactness": "close", "note": "Designations are set by state departments of transportation rather than nationally, so \"crusher run\" describes the production method and the actual grading depends on the specifying agency." }, { "market": "CA", "term": "granular base", "alsoCalled": [ "Granular A", "Granular B", "crusher run" ], "exactness": "close", "note": "Provincial designations such as Granular A and Granular B name specific gradings, so the letter matters and does not translate to a British or American product name." }, { "market": "AU", "term": "road base", "alsoCalled": [ "DGB", "dense graded base", "crushed rock" ], "exactness": "close", "note": "Australian designations are set by state road authorities to their own specifications, so a class name identifies a grading in that state rather than a material available everywhere." } ], "standards": [ { "market": "UK", "standard": "SHW Series 800", "covers": "Unbound mixtures for sub-base — grading and compaction requirements." }, { "market": "US", "standard": "AASHTO M147", "covers": "Materials for aggregate and soil-aggregate subbase, base and surface courses." } ], "calculators": [ { "slug": "gravel-base-tonnage-calculator", "json": "https://craftquantities.com/api/v1/calculators/gravel-base-tonnage-calculator.json" }, { "slug": "base-course-tonnage-calculator", "json": "https://craftquantities.com/api/v1/calculators/base-course-tonnage-calculator.json" }, { "slug": "gravel-driveway-calculator", "json": "https://craftquantities.com/api/v1/calculators/gravel-driveway-calculator.json" }, { "slug": "open-graded-bedding-course-calculator", "json": "https://craftquantities.com/api/v1/calculators/open-graded-bedding-course-calculator.json" }, { "slug": "separation-geotextile-roll-calculator", "json": "https://craftquantities.com/api/v1/calculators/separation-geotextile-roll-calculator.json" } ], "confusions": [ { "question": "Is hardcore the same as sub-base?", "answer": "Not quite, and the difference is a specification. Sub-base names the LAYER and, in modern British practice, a material graded to a published envelope — MOT Type 1 being the familiar one, a crushed rock with a controlled range of particle sizes so that it compacts to a dense, interlocked, load-spreading layer. Hardcore is the older and looser term, historically covering broken brick, demolition arisings and whatever hard material was available, laid to fill and to raise levels. The two are often used interchangeably on domestic work, and the distinction matters where performance is required: unspecified hardcore may contain material that degrades, holds water, or contains sulfates that attack concrete above it." }, { "question": "Why do the designations not translate between markets?", "answer": "Because they are product specifications issued by different authorities, not descriptions of a generic material. A British MOT Type 1 is defined by a grading envelope in a national specification for highway works. American aggregate base designations are issued by individual state departments of transportation, so the same trade name can mean different gradings in neighbouring states. Canadian Granular A and B are provincial designations, and Australian road base classes are set by state road authorities. So the correct approach when reading a foreign specification is to find the grading and the compaction requirement it actually calls for, and match those against a locally available product, rather than to look for the nearest-sounding name." }, { "question": "How thick should it be?", "answer": "It depends on the subgrade beneath and the loading above, which is why it is designed rather than defaulted. The layer's job is to spread concentrated loads from the surface into ground that cannot take them directly, so a weak or wet subgrade needs a thicker layer than a firm one, and a drive taking occasional cars needs far less than a yard taking loaded lorries. The subgrade's strength is measured — by CBR or an equivalent — and the thickness follows from that and the design traffic. Thickness is also constrained from below by compaction: the layer is built in lifts a compactor can actually densify through, so a thick sub-base is several passes of placing and compacting rather than one." } ], "related": [ "tarmac", "kerb", "sand", "aggregate-size", "paving-flag", "soakaway", "slab-on-grade" ] }, { "slug": "nominal-size", "concept": "Nominal size (the 2x4 problem)", "family": "measurement", "definition": "A size a product is NAMED by rather than measured at. A North American 2x4 is smaller than two inches by four in both directions; a metric sawn section may be quoted sawn or planed. The designation identifies the product, not its dimensions.", "url": "https://craftquantities.com/glossary/nominal-size/", "names": [ { "market": "US", "term": "nominal size", "alsoCalled": [ "2x4", "dimensional lumber" ], "exactness": "false-friend", "note": "The name is imperial and pre-drying; the actual piece is smaller in both directions by an amount fixed in the grading rules, so the designation is an identifier rather than a measurement." }, { "market": "CA", "term": "nominal size", "alsoCalled": [ "2x4", "dimension lumber" ], "exactness": "false-friend", "note": "As the United States, with the same nominal-versus-actual gap, and the actual sizes stated in millimetres alongside the imperial name." }, { "market": "UK", "term": "sawn size", "alsoCalled": [ "nominal size", "ex-size", "regularised", "PAR" ], "exactness": "false-friend", "note": "British timber quotes the SAWN size, with the planed piece smaller — \"ex 50 x 100\" means sawn at that and delivered under it, which is a different convention from the American one, not a translation of it." }, { "market": "AU", "term": "nominal size", "alsoCalled": [ "sawn size", "dressed size", "DAR" ], "exactness": "false-friend", "note": "Australian practice distinguishes sawn from dressed (DAR) sizes explicitly, so the same board has two published dimensions and which is quoted depends on how it is sold." } ], "standards": [ { "market": "US", "standard": "PS 20", "covers": "American Softwood Lumber Standard — the nominal-to-actual size relationship." }, { "market": "UK", "standard": "BS EN 1313-1", "covers": "Round and sawn timber — permitted deviations and preferred sizes for softwood." } ], "calculators": [ { "slug": "lumber-dimensional-size-calculator", "json": "https://craftquantities.com/api/v1/calculators/lumber-dimensional-size-calculator.json" }, { "slug": "board-foot-lumber-cost-calculator", "json": "https://craftquantities.com/api/v1/calculators/board-foot-lumber-cost-calculator.json" }, { "slug": "deck-joist-span-calculator", "json": "https://craftquantities.com/api/v1/calculators/deck-joist-span-calculator.json" } ], "confusions": [ { "question": "Why is a 2x4 not two inches by four?", "answer": "Because it is named for its size before it was dried and planed. Timber is sawn oversized from green stock, then dried — which shrinks it — and then surfaced on all four faces, which removes more. The finished piece is smaller in both directions by amounts fixed in the grading rules, so every 2x4 from every mill arrives at the same actual size and the name survives as an identifier. The same applies to every nominal designation in the family. It matters because the DEPTH is what governs a joist or a rafter: bending stiffness rises with the cube of depth, so treating a nominal depth as an actual one over-estimates the member substantially, and span tables are written against the actual size for exactly that reason." }, { "question": "What is the metric equivalent of a 2x4?", "answer": "There is not one, only a nearest size — and that is the honest answer rather than a cautious one. Metric sawn timber is produced to its own preferred sizes, which were not derived by converting the imperial ones, so the nearest metric section to a 2x4 differs from it in both dimensions by a few millimetres in whichever direction the local standard chose. A few millimetres of depth is a real change in stiffness, and a few millimetres of width changes how sheet material lands on the framing. So substituting across the systems is a design decision checked against a span table, not a conversion; and a detail drawn for one module — 16 or 24 inch centres against 400 or 600 mm — does not land on the other." }, { "question": "What do ex-size, regularised, PAR and DAR mean?", "answer": "They are the British and Australian ways of saying how much machining has happened since the piece was sawn, and therefore which dimension is being quoted. \"Ex\" a size means sawn at that size and delivered smaller after processing. Regularised means machined to a consistent depth so that joists line up, with the width left sawn. PAR — planed all round — and the Australian DAR, dressed all round, mean surfaced on all four faces and therefore smaller again in both directions. Each has its own published tolerance from the sawn size. A quantity taken from a drawing in sawn sizes and ordered in planed ones is short in every dimension, which shows up as gaps at the sheathing rather than as an obvious error." } ], "related": [ "timber", "joist", "stair-going", "gauge", "tolerance" ] }, { "slug": "soffit", "concept": "Soffit and fascia", "family": "envelope", "definition": "The trim closing the roof's overhang: the soffit is the horizontal underside between the wall and the edge of the eaves, and the fascia is the vertical board at the edge, to which the gutter is normally fixed.", "url": "https://craftquantities.com/glossary/soffit/", "names": [ { "market": "US", "term": "soffit", "alsoCalled": [ "fascia", "rake board" ], "exactness": "close", "note": "\"Soffit\" also names the underside of any building element in American usage — a beam, an arch, a dropped ceiling — so the eaves sense is one of several." }, { "market": "CA", "term": "soffit", "alsoCalled": [ "fascia" ], "exactness": "close", "note": "As the United States, with the same broader use of soffit for the underside of any element rather than the eaves specifically." }, { "market": "UK", "term": "soffit", "alsoCalled": [ "fascia", "barge board", "eaves board" ], "exactness": "close", "note": "British usage adds \"barge board\" for the sloping board at a gable end, which American usage calls a rake board — a different member from the fascia." }, { "market": "AU", "term": "eaves lining", "alsoCalled": [ "soffit", "fascia", "barge board" ], "exactness": "close", "note": "Australian practice commonly says \"eaves lining\" for the sheet material forming the soffit, which names the material rather than the position." } ], "standards": [], "calculators": [ { "slug": "soffit-panel-calculator", "json": "https://craftquantities.com/api/v1/calculators/soffit-panel-calculator.json" }, { "slug": "fascia-board-calculator", "json": "https://craftquantities.com/api/v1/calculators/fascia-board-calculator.json" }, { "slug": "soffit-bulkhead-wrap-area-calculator", "json": "https://craftquantities.com/api/v1/calculators/soffit-bulkhead-wrap-area-calculator.json" } ], "confusions": [ { "question": "What is the difference between a soffit and a fascia?", "answer": "Orientation and job. The fascia is the vertical board running along the lower edge of the roof, fixed to the ends of the rafters or the truss tails; it closes the end grain, carries the gutter, and is the piece that takes the weather and the water. The soffit is the horizontal panel underneath, spanning from the fascia back to the wall, closing the void beneath the overhang. In many houses they are supplied as a matching system and replaced together, which is why the words get used loosely — but they are different members, in different planes, doing different jobs, and a quote for one is not a quote for the other." }, { "question": "Why is soffit ventilation so important?", "answer": "Because for a ventilated roof it is the INTAKE, and an intake that does not work makes the outlet useless. A ventilated roof space relies on air entering low at the eaves and leaving high at the ridge, driven by buoyancy and wind, to carry away moisture and to keep the roof deck cold enough to prevent ice damming in cold climates. That low intake is through the soffit, whether as a continuous vent strip, perforated panels or discrete vents. The common failure is insulation pushed out over the wall plate until it blocks the path — which is why baffles exist — and the second is a replacement soffit fitted without vents because the old one appeared solid. Either leaves a roof that ventilates on paper." }, { "question": "What is a barge board, and does it have an American name?", "answer": "The sloping board along the edge of a gable, following the roof's pitch up to the apex, rather than the horizontal board along the eaves. British and Australian usage calls it a barge board; American usage calls the same member a rake board, from the raked or sloping edge it follows. It does a similar job to a fascia — closing the edge, protecting the ends of the battens or the roof sheathing, and finishing the line — but it does not carry a gutter and it meets the roof at a different angle, so its profile and its fixing differ. A specification that uses \"fascia\" for both is losing a distinction that changes the material take-off." } ], "related": [ "gutter", "verge" ] }, { "slug": "tarmac", "concept": "Asphalt / tarmac / blacktop", "family": "site", "definition": "The bound surfacing used on roads, drives and yards: mineral aggregate held together by a bituminous binder, laid hot and compacted. The everyday names for it differ by market, and one of them names a material almost nobody still lays.", "url": "https://craftquantities.com/glossary/tarmac/", "names": [ { "market": "US", "term": "asphalt", "alsoCalled": [ "blacktop", "hot mix asphalt", "HMA" ], "exactness": "close", "note": "In American usage \"asphalt\" names both the BINDER and the finished mix, which is the reverse of British usage where bitumen is the binder and asphalt the mix." }, { "market": "CA", "term": "asphalt", "alsoCalled": [ "blacktop" ], "exactness": "close", "note": "As the United States, with the same double duty: asphalt is both the binder and the laid material depending on context." }, { "market": "UK", "term": "asphalt", "alsoCalled": [ "tarmac", "bitumen macadam", "blacktop" ], "exactness": "false-friend", "note": "\"Tarmac\" is a trade name for a tar-bound material that is essentially no longer laid — modern surfacing is bitumen-bound — so the everyday British word names the wrong binder." }, { "market": "AU", "term": "asphalt", "alsoCalled": [ "bitumen", "hotmix" ], "exactness": "false-friend", "note": "Australian site usage often calls the finished surface \"bitumen\", which in British and technical usage is the BINDER rather than the mix — the same word doing a different job." } ], "standards": [ { "market": "US", "standard": "ASTM D6926 / Superpave", "covers": "Asphalt mixture design and specimen preparation." }, { "market": "UK", "standard": "BS EN 13108", "covers": "Bituminous mixtures — material specifications." } ], "calculators": [ { "slug": "asphalt-driveway-calculator", "json": "https://craftquantities.com/api/v1/calculators/asphalt-driveway-calculator.json" }, { "slug": "asphalt-cubic-yards-to-tons-calculator", "json": "https://craftquantities.com/api/v1/calculators/asphalt-cubic-yards-to-tons-calculator.json" }, { "slug": "asphalt-crack-filler-calculator", "json": "https://craftquantities.com/api/v1/calculators/asphalt-crack-filler-calculator.json" }, { "slug": "aashto-structural-number-calculator", "json": "https://craftquantities.com/api/v1/calculators/aashto-structural-number-calculator.json" }, { "slug": "asphalt-in-place-density-gmm-calculator", "json": "https://craftquantities.com/api/v1/calculators/asphalt-in-place-density-gmm-calculator.json" }, { "slug": "asphalt-pavement-esal-calculator", "json": "https://craftquantities.com/api/v1/calculators/asphalt-pavement-esal-calculator.json" } ], "confusions": [ { "question": "Is tarmac the same as asphalt?", "answer": "Not technically, and the difference is the binder. Tarmac is short for tarmacadam — crushed stone bound with TAR, a by-product of coal processing — and it is a genuine historic material that has been almost entirely replaced by bitumen-bound mixtures, because tar is a petroleum-free by-product that became scarce and carries health concerns. What is laid on a British drive or road today is asphalt: the same aggregate idea with a bitumen binder. The word survives in everyday speech, in airport tarmac, and as a trade name, so a client asking for tarmac and a contractor quoting asphalt are describing the same work — but a specification that says tar means something a supplier cannot deliver." }, { "question": "What is the difference between bitumen and asphalt?", "answer": "In British and technical usage, bitumen is the BINDER — the black viscous material that holds the aggregate together — and asphalt is the finished mixture of binder and aggregate. In American usage \"asphalt\" does both jobs: asphalt cement is the binder, and asphalt or hot mix asphalt is the laid material, with context distinguishing them. Australian site usage adds a third pattern, calling the finished surface bitumen. None of these is wrong within its own market, and all three appear in documents that cross markets — so a specification naming a grade of bitumen and one naming a grade of asphalt may be talking about the same property or about two different layers of the same construction." }, { "question": "Does the surfacing come in one layer?", "answer": "Rarely, and the layer names are another place the markets diverge. A bound surfacing is normally built in courses: a thicker, coarser lower layer that carries the load and a thinner, finer upper layer that provides the running surface and the texture. British practice calls them binder course and surface course, with a base beneath; American practice names a base course, an intermediate or binder course and a wearing or surface course. The materials, the aggregate sizes and the compaction requirements differ by layer, so a thickness quoted without saying which course it refers to is ambiguous — and a drive laid as one thick layer of surface-course material is a different construction from one laid properly in two." } ], "related": [ "hardcore", "hardstanding" ] }, { "slug": "roof-pitch", "concept": "Roof pitch", "family": "measurement", "definition": "How steep a roof is. It is expressed as a rise per unit of run, as a ratio, or as an angle in degrees — three conventions for one property, and a figure quoted without its convention is ambiguous.", "url": "https://craftquantities.com/glossary/roof-pitch/", "names": [ { "market": "US", "term": "pitch (rise in 12)", "alsoCalled": [ "6:12", "6 in 12", "slope" ], "exactness": "false-friend", "note": "A bare number means inches of rise per 12 inches of run, NOT degrees — so \"a 6 pitch\" is about 26.6 degrees, not six." }, { "market": "CA", "term": "pitch (rise in 12)", "alsoCalled": [ "6:12", "slope" ], "exactness": "false-friend", "note": "As the United States: the run is 12 even where the rest of the drawing is metric, because the convention travelled with the framing practice." }, { "market": "UK", "term": "pitch (degrees)", "alsoCalled": [ "fall", "rise and run" ], "exactness": "false-friend", "note": "British practice quotes the ANGLE in degrees, so a pitch given as a bare number means degrees — the opposite reading from the American one." }, { "market": "AU", "term": "pitch (degrees)", "alsoCalled": [ "fall", "roof slope" ], "exactness": "false-friend", "note": "As the UK, degrees — and manufacturers' minimum pitches for tiles and sheeting are published in degrees, so converting from a ratio is a required step rather than a convenience." } ], "standards": [ { "market": "UK", "standard": "BS 5534", "covers": "Slating and tiling — including minimum pitch and fixing requirements." }, { "market": "US", "standard": "IRC Chapter 9", "covers": "Roof assemblies, including minimum slopes by covering type." } ], "calculators": [ { "slug": "roof-pitch-to-degrees-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-pitch-to-degrees-calculator.json" }, { "slug": "degrees-to-roof-pitch-calculator", "json": "https://craftquantities.com/api/v1/calculators/degrees-to-roof-pitch-calculator.json" }, { "slug": "common-rafter-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/common-rafter-length-calculator.json" } ], "confusions": [ { "question": "Is a 6 pitch six degrees?", "answer": "No, and this is the one that produces a roof of the wrong shape. In American and Canadian usage a pitch of 6 means six units of rise for every twelve of run — an angle of about 26.6 degrees. In British and Australian usage a pitch of 6 means six DEGREES, which is a nearly flat roof. The two readings of the same bare number are far apart, and neither convention marks itself: a drawing saying \"pitch 6\" is unambiguous only to a reader who knows which market drew it. Converting is straightforward arithmetic — the angle is the arctangent of rise over run — but it has to be done deliberately, and the convention has to be stated on anything read across markets." }, { "question": "What is the difference between pitch and slope?", "answer": "In careful American usage they are different ratios, though the words are used loosely. Slope is the rise over the horizontal RUN — the 6-in-12 figure — and it is what framing, rafter lengths and covering minimums are worked from. Pitch, in its older and stricter sense, is the rise over the total SPAN of the building, so the same roof has a slope of 6 in 12 and a pitch of one quarter. In everyday use the word pitch has taken over the slope meaning almost everywhere, which is why the strict sense mostly appears in older texts and in some truss literature. If a document uses both words for different numbers, that is probably why." }, { "question": "Why do minimum pitches matter so much?", "answer": "Because a roof covering sheds water rather than sealing against it, and below a certain angle it stops shedding fast enough. Tiles, slates and profiled sheets each have a manufacturer's minimum pitch, below which wind-driven rain is pushed back up under the laps faster than it drains away — so the covering leaks even though every piece is correctly fixed. The minimum is not a single number per material: it depends on the lap, on the underlay, on the exposure of the site, and often on whether the sheets are sealed at the laps. Below the lowest tiled pitch the construction changes entirely to a continuously supported membrane, which is a different trade and a different detail." } ], "related": [] }, { "slug": "skim", "concept": "Skim coat / joint compound", "family": "finishes", "definition": "The material applied over plasterboard to produce the surface that gets decorated. British practice normally coats the whole wall thinly; North American practice normally fills and feathers only the joints and the fixing heads.", "url": "https://craftquantities.com/glossary/skim/", "names": [ { "market": "UK", "term": "skim", "alsoCalled": [ "skim coat", "finish plaster", "multi-finish" ], "exactness": "false-friend", "note": "A thin gypsum plaster over the WHOLE surface, applied by a plasterer — not a joint treatment, and the quantity is an area rather than a length of joint." }, { "market": "AU", "term": "set", "alsoCalled": [ "skim", "topping compound" ], "exactness": "false-friend", "note": "Australian practice more often follows the jointed approach than the British full skim, so the word appears in both senses and which is meant depends on the specification." }, { "market": "US", "term": "joint compound", "alsoCalled": [ "mud", "taping compound", "skim coat (level 5)" ], "exactness": "false-friend", "note": "Normally applied only at the JOINTS and fixings. A full-surface coat exists as the highest finish level and is a specified extra rather than the default." }, { "market": "CA", "term": "joint compound", "alsoCalled": [ "mud", "drywall compound" ], "exactness": "false-friend", "note": "As the United States, including the finish-level system — so \"finished drywall\" describes a level rather than a full-surface coat." } ], "standards": [ { "market": "US", "standard": "ASTM C840 / GA-214", "covers": "Application of gypsum board and the levels of finish." }, { "market": "UK", "standard": "BS 8481 / BS EN 13279", "covers": "Design and application of plasterboard finishing, and gypsum binders." } ], "calculators": [ { "slug": "drywall-joint-compound-calculator", "json": "https://craftquantities.com/api/v1/calculators/drywall-joint-compound-calculator.json" }, { "slug": "plaster-finish-coat-calculator", "json": "https://craftquantities.com/api/v1/calculators/plaster-finish-coat-calculator.json" }, { "slug": "drywall-calculator", "json": "https://craftquantities.com/api/v1/calculators/drywall-calculator.json" } ], "confusions": [ { "question": "What is the difference between skimming and taping?", "answer": "How much of the wall gets covered, which changes the material, the trade and the quantity. British practice normally applies a thin gypsum plaster over the ENTIRE board surface — the skim — producing a continuous, dense, smooth finish that is painted directly. North American practice tapes and fills only the joints and the fixing heads, feathering the compound out and sanding it flush, leaving most of the paper face as the painted surface. The first is priced by area and done by a plasterer; the second is priced by joint length and done by a taper. Reading one specification with the other in mind gets both the labour and the material wrong." }, { "question": "What are drywall finish levels?", "answer": "A North American system describing how much finishing has been done, from the board simply fixed with nothing applied, through progressively more taping and coats, up to a level where a thin skim covers the whole surface. The point of the system is that it makes the requirement explicit: the finish that suits a warehouse is not the finish that suits a wall in raking light, and the difference is a specified level rather than a matter of care. The highest level is effectively what a British skim produces by default, which is the clearest way to see that the two traditions bracket the same range of outcomes and simply put their default in a different place." }, { "question": "Why does raking light expose one and not the other?", "answer": "Because a jointed finish has a shallow profile the full-surface coat does not. Filling a joint means building compound over the taper and feathering it out, which leaves a very slight rise and a change of texture where the compound meets the paper — invisible under diffuse light and clearly visible under light striking the wall at a shallow angle, which is what a window or a wall-washer does. A full skim removes the distinction by covering everything in the same material to the same density. That is why the higher finish levels exist and why they are specified for walls in critical lighting, and it is a common source of dispute when a specification does not name the level." } ], "related": [ "plasterboard", "lath" ] }, { "slug": "soil-pipe", "concept": "Soil, waste and vent pipework", "family": "services", "definition": "The above-ground drainage that carries used water and sewage out of a building, plus the air path that keeps the water seals in its traps intact.", "url": "https://craftquantities.com/glossary/soil-pipe/", "names": [ { "market": "UK", "term": "soil and vent pipe (SVP)", "alsoCalled": [ "soil stack", "waste pipe", "above-ground drainage" ], "exactness": "false-friend", "note": "British practice separates SOIL (from WCs) from WASTE (from basins, baths, sinks) as distinct terms — so \"waste\" excludes sewage rather than including it." }, { "market": "AU", "term": "sanitary plumbing", "alsoCalled": [ "soil stack", "waste", "stack" ], "exactness": "close", "note": "Australian practice keeps the soil-and-waste distinction in its terminology but groups both under sanitary plumbing, with its own venting rules." }, { "market": "US", "term": "DWV", "alsoCalled": [ "drain-waste-vent", "soil stack", "waste line" ], "exactness": "false-friend", "note": "DWV bundles all of it into one system name, and American \"waste\" commonly covers everything including sewage — the opposite of the narrower British sense." }, { "market": "CA", "term": "DWV", "alsoCalled": [ "drain-waste-vent", "sanitary drainage" ], "exactness": "false-friend", "note": "As the United States for the terminology, with Canadian venting provisions differing in detail — so the words map and the permitted arrangements do not." } ], "standards": [ { "market": "UK", "standard": "BS EN 12056-2", "covers": "Sanitary pipework — layout, calculation and venting." }, { "market": "US", "standard": "IPC / UPC", "covers": "Drainage fixture units, pipe sizing and venting requirements." }, { "market": "AU", "standard": "AS/NZS 3500.2", "covers": "Sanitary plumbing and drainage." } ], "calculators": [ { "slug": "drain-pipe-slope-calculator", "json": "https://craftquantities.com/api/v1/calculators/drain-pipe-slope-calculator.json" }, { "slug": "storm-drain-slope-calculator", "json": "https://craftquantities.com/api/v1/calculators/storm-drain-slope-calculator.json" }, { "slug": "septic-tank-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/septic-tank-sizing-calculator.json" } ], "confusions": [ { "question": "Does waste mean the same thing everywhere?", "answer": "No, and the British sense is narrower than the American one. In British practice SOIL is the discharge from WCs and urinals, and WASTE is the discharge from basins, baths, showers and sinks — two named categories with different pipe sizes, different gradients and historically different routes. In American practice the drain-waste-vent system names everything together and \"waste line\" commonly covers all of it. So a British specification calling for a waste pipe is describing something that does not carry sewage, and reading it with the American sense will size the wrong pipe and route it to the wrong place." }, { "question": "What is the vent actually for?", "answer": "Keeping the water seals in the traps intact, which is what stops drain air entering the building. Every fixture has a trap holding a small depth of water, and that seal can be broken two ways: a discharge running past the trap can siphon the water out, and a surge elsewhere can push the water back through it. A vent path connected to the system equalises the pressure on both sides of the seal, so neither happens. Every market requires venting and all of them permit several arrangements — a full vent stack, individual vents, air admittance valves where the code allows them — and the permitted arrangements differ, so a layout valid in one jurisdiction may not be in another." }, { "question": "Why is the fall of a drain a specified range rather than a minimum?", "answer": "Because too much fall is a defect as well as too little. A pipe laid too shallow does not develop enough velocity to carry solids and silts up; a pipe laid too steep lets the water run away from the solids, which are left behind and build up — the same blockage from the opposite cause. So codes give a gradient range for each pipe size, and the correct answer is within it rather than as steep as the site allows. The related trap is a pipe laid to a nominal gradient over a long run without checking intermediate levels, which produces a series of shallow and steep sections averaging correctly and behaving as neither." } ], "related": [ "stopcock", "trap", "manhole", "flue" ] }, { "slug": "osb", "concept": "OSB, chipboard and particle board", "family": "materials", "definition": "Engineered wood panels made from wood particles bonded with resin. They differ in the size and orientation of those particles, which is what separates a structural sheathing board from a furniture panel.", "url": "https://craftquantities.com/glossary/osb/", "names": [ { "market": "UK", "term": "OSB", "alsoCalled": [ "oriented strand board", "sterling board" ], "exactness": "false-friend", "note": "British \"chipboard\" means the fine-particle furniture and flooring panel, NOT OSB — so a substitution between them swaps a structural board for one that is not." }, { "market": "US", "term": "OSB", "alsoCalled": [ "oriented strand board", "sheathing" ], "exactness": "false-friend", "note": "American \"particle board\" is the fine-particle panel British usage calls chipboard; the word chipboard is uncommon there and can be read as either." }, { "market": "CA", "term": "OSB", "alsoCalled": [ "waferboard", "particleboard (the fine panel)" ], "exactness": "close", "note": "Waferboard is an older related product with larger, unoriented flakes — structurally weaker than OSB and not a synonym for it." }, { "market": "AU", "term": "OSB", "alsoCalled": [ "structural particleboard", "chipboard flooring" ], "exactness": "close", "note": "Australian practice uses structural particleboard for flooring far more than OSB, so the common sheet in a floor is a different product from the North American default." } ], "standards": [ { "market": "UK", "standard": "BS EN 300", "covers": "Oriented strand boards — definitions, classification and requirements." }, { "market": "US", "standard": "PS 2 / APA rating", "covers": "Performance standard for wood structural panels, with span ratings." } ], "calculators": [ { "slug": "plywood-sheet-calculator", "json": "https://craftquantities.com/api/v1/calculators/plywood-sheet-calculator.json" }, { "slug": "roof-sheathing-nail-count-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-sheathing-nail-count-calculator.json" }, { "slug": "lumber-dimensional-size-calculator", "json": "https://craftquantities.com/api/v1/calculators/lumber-dimensional-size-calculator.json" } ], "confusions": [ { "question": "Is chipboard the same as OSB?", "answer": "Not in British usage, and the difference is structural rather than cosmetic. OSB is made from large wood STRANDS laid in oriented layers and bonded under pressure, which gives it directional strength and stiffness suitable for sheathing walls and roofs and for structural flooring. Chipboard, in British usage, is made from small particles with no orientation, which makes it dimensionally convenient and considerably weaker — it is the panel used for furniture carcasses and for some flooring grades. Substituting one for the other because both are described as engineered wood panels puts a non-structural board where a structural one was specified, and it is the moisture behaviour that usually reveals it first." }, { "question": "What does a span rating tell you?", "answer": "The maximum spacing of supports the panel is rated for, which is the property that actually matters when sheathing or decking. North American structural panels carry a rating that names the permitted spacing for roof and floor use, so a sheet can be selected against the framing centres directly rather than by thickness alone — two panels of the same thickness from different products can have different ratings. European and British practice specifies the board by its grade and its structural class instead, with load-span tables published separately. Either way, thickness on its own is not a specification: it is the rating or the class, against the support spacing and the load, that decides whether a panel is adequate." }, { "question": "How do these boards behave when they get wet?", "answer": "Differently, and it is the property that most often decides which is acceptable. Standard chipboard and particle board swell substantially and largely irreversibly when wetted, particularly at cut edges, and they lose strength as they do — which is why a flooded floor of standard board is replaced rather than dried. OSB swells too, mostly at the edges, but generally retains more of its strength and is manufactured in grades intended for humid conditions and for temporary exposure during construction. Moisture-resistant grades of both exist and are a specified product rather than a general property. None of them is a waterproof board, and none should be left exposed to weather beyond the period its grade allows." } ], "related": [ "timber", "chipboard", "plywood" ] }, { "slug": "rsj", "concept": "Steel beam designations", "family": "structure", "definition": "The I-shaped rolled steel sections used as beams and columns. Every market names them by its own system, and the systems encode different properties — so a designation cannot be read across a border without a section table.", "url": "https://craftquantities.com/glossary/rsj/", "names": [ { "market": "UK", "term": "universal beam (UB)", "alsoCalled": [ "RSJ", "universal column (UC)", "I-beam" ], "exactness": "false-friend", "note": "\"RSJ\" strictly means the older rolled steel joist with tapered flanges, largely superseded by UB and UC — but it survives in speech for any steel beam, which is why it is an unreliable word in a specification." }, { "market": "AU", "term": "universal beam (UB)", "alsoCalled": [ "UC", "universal column" ], "exactness": "close", "note": "The naming convention follows the British one, but the available section sizes are the Australian range and the designations are not interchangeable with British ones." }, { "market": "US", "term": "W-shape", "alsoCalled": [ "wide flange", "W12x26", "I-beam" ], "exactness": "false-friend", "note": "A W designation gives nominal depth and WEIGHT PER FOOT, where a UB designation gives depth, width and mass per metre — the numbers encode different things." }, { "market": "CA", "term": "W-shape", "alsoCalled": [ "wide flange" ], "exactness": "close", "note": "As the United States for the naming, with the designations stated in metric — so a Canadian W section number is not the same number as the American one for the same member." } ], "standards": [ { "market": "UK", "standard": "BS EN 1993 (Eurocode 3)", "covers": "Design of steel structures." }, { "market": "US", "standard": "AISC 360", "covers": "Specification for structural steel buildings, with the section property tables." }, { "market": "AU", "standard": "AS 4100", "covers": "Steel structures." } ], "calculators": [ { "slug": "steel-beam-camber-calculator", "json": "https://craftquantities.com/api/v1/calculators/steel-beam-camber-calculator.json" }, { "slug": "steel-moment-connection-bolt-calculator", "json": "https://craftquantities.com/api/v1/calculators/steel-moment-connection-bolt-calculator.json" }, { "slug": "plate-block-shear-net-section-calculator", "json": "https://craftquantities.com/api/v1/calculators/plate-block-shear-net-section-calculator.json" } ], "confusions": [ { "question": "Is an RSJ the same as a universal beam?", "answer": "Strictly no, though the words are used as though they were. A rolled steel joist is an older section with TAPERED flanges, and it has largely been superseded in British practice by the universal beam and universal column, which have parallel flanges — a shape that is easier to connect to, easier to bolt through and more efficient in bending. The word survived the product: in everyday British site and domestic use, any steel beam over an opening is called an RSJ. That is harmless in conversation and unhelpful in a specification, because a fabricator asked for an RSJ has to decide whether a genuine tapered-flange section is meant or whether the ordinary UB is intended." }, { "question": "What do the numbers in a designation mean?", "answer": "Different things in each system, which is why they cannot be compared directly. An American W designation gives a nominal depth followed by the weight per foot, so the second number is a mass rather than a dimension and two sections of the same nominal depth can have quite different actual depths. A British or Australian universal beam designation gives the serial size — depth and width — followed by the mass per metre. So a designation carries depth-and-mass in one system and depth-width-and-mass in the other, and the nominal depth in the American system is not necessarily the actual depth. Reading either across requires the section tables rather than arithmetic." }, { "question": "What is the difference between a beam and a column section?", "answer": "Proportions, chosen for the job. A universal beam is deep relative to its width, because bending stiffness grows with depth and a beam's job is to resist bending over a span. A universal column is closer to square, because a column resists buckling about BOTH axes and a deep narrow section is weak about its minor axis. The American W range covers both duties within one designation family rather than splitting the names, so the distinction there is made by choosing proportions rather than by the prefix. Using a beam section as a column, or the reverse, is a real error rather than a preference, and it is easier to make when reading a designation from an unfamiliar system." } ], "related": [ "reinforcement", "lintel", "padstone", "steel-grade" ] }, { "slug": "kerb", "concept": "Kerb / curb", "family": "site", "definition": "The raised edge between a carriageway and a footway or verge, which contains the surfacing, defines the channel that carries surface water, and separates vehicles from pedestrians.", "url": "https://craftquantities.com/glossary/kerb/", "names": [ { "market": "UK", "term": "kerb", "alsoCalled": [ "kerbstone", "kerb and channel" ], "exactness": "close", "note": "Spelled with a K. British \"curb\" is the unrelated verb meaning to restrain, so the spelling carries the meaning rather than being a variant." }, { "market": "AU", "term": "kerb", "alsoCalled": [ "kerb and gutter", "K&G" ], "exactness": "close", "note": "British spelling, and \"kerb and gutter\" is the standard phrase for the combined edge-and-channel unit rather than two separate elements." }, { "market": "US", "term": "curb", "alsoCalled": [ "curb and gutter", "concrete curb" ], "exactness": "close", "note": "Spelled with a C, and normally cast in place as a continuous curb-and-gutter section rather than laid as precast units." }, { "market": "CA", "term": "curb", "alsoCalled": [ "curb and gutter" ], "exactness": "close", "note": "American spelling and generally American practice — cast in place — though precast units appear in some municipal specifications." } ], "standards": [ { "market": "UK", "standard": "BS EN 1340", "covers": "Concrete kerb units — requirements and test methods." }, { "market": "US", "standard": "AASHTO / state DOT standards", "covers": "Curb and gutter geometry and construction, specified by the highway authority." } ], "calculators": [ { "slug": "curb-gutter-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/curb-gutter-volume-calculator.json" }, { "slug": "concrete-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-calculator.json" }, { "slug": "base-course-tonnage-calculator", "json": "https://craftquantities.com/api/v1/calculators/base-course-tonnage-calculator.json" } ], "confusions": [ { "question": "Is the gutter beside a kerb the same as a roof gutter?", "answer": "No, and it is the collision worth knowing about because both words are unqualified in their own trades. The gutter beside a kerb is the shallow channel formed between the kerb face and the carriageway surface, which collects surface water and carries it along the road to a gully. The gutter at a roof's eaves is a fixed channel collecting water off the roof. They share a word because they share a function — a channel carrying water along an edge — and nothing else: different trades, different materials, different standards and different calculations. A drawing note about gutter falls means one of them, and which one depends entirely on which drawing it is." }, { "question": "Why is the kerb face height a specified dimension?", "answer": "Because several requirements meet at it and they pull in different directions. The face has to be high enough to contain the surfacing, to keep vehicles off the footway, and to give the channel enough depth to carry the design flow to the next gully. It has to be low enough that a vehicle mounting it at a crossing does not strike its underside, and at pedestrian crossing points it is dropped flush, or nearly so, for accessibility — which is a regulated dimension rather than a preference. So a kerb run is normally several specified heights: full face along the road, a transition, and a dropped section at each crossing and each vehicle access." }, { "question": "Precast units or cast in place?", "answer": "A genuine difference in practice between the markets, and it changes the quantities and the programme rather than the design intent. British and Australian work commonly lays precast concrete kerb units on a concrete bed with a concrete backing, so the quantity is a length of units plus the bedding and haunching concrete. North American practice more often casts the curb and gutter in one continuous operation with a slipform machine or in formwork, so the quantity is a volume of concrete and the unit rate is per length of extrusion. Radii, transitions and dropped sections are where the two diverge most: precast needs specific radius units, and cast-in-place simply follows the form." } ], "related": [ "hardcore" ] }, { "slug": "loft", "concept": "Loft / attic", "family": "structure", "definition": "The space between the top-floor ceiling and the roof. Whether it is insulated at the ceiling or at the roof slope decides whether it is inside or outside the building's thermal envelope.", "url": "https://craftquantities.com/glossary/loft/", "names": [ { "market": "UK", "term": "loft", "alsoCalled": [ "roof space", "attic" ], "exactness": "false-friend", "note": "In British property usage a \"loft apartment\" is an American idea entirely — a converted industrial floor — while a British \"loft conversion\" is a room made in the roof space of a house." }, { "market": "AU", "term": "roof space", "alsoCalled": [ "attic", "loft" ], "exactness": "close", "note": "Australian construction usage favours \"roof space\" for the void, with attic reserved for one converted to a habitable room." }, { "market": "US", "term": "attic", "alsoCalled": [ "roof space" ], "exactness": "false-friend", "note": "\"Loft\" in American usage means either an open mezzanine within a room or a converted industrial apartment — not the roof void, which is the attic." }, { "market": "CA", "term": "attic", "alsoCalled": [ "roof space" ], "exactness": "close", "note": "As the United States, with attic the standard word for the void and loft carrying the mezzanine or apartment sense." } ], "standards": [ { "market": "UK", "standard": "Approved Document B / L", "covers": "Fire escape and thermal requirements for habitable rooms in a roof." }, { "market": "US", "standard": "IRC Chapter 8", "covers": "Roof-ceiling construction, including attic ventilation and access." } ], "calculators": [ { "slug": "attic-ventilation-calculator", "json": "https://craftquantities.com/api/v1/calculators/attic-ventilation-calculator.json" }, { "slug": "attic-insulation-upgrade-calculator", "json": "https://craftquantities.com/api/v1/calculators/attic-insulation-upgrade-calculator.json" }, { "slug": "loft-conversion-cost-calculator", "json": "https://craftquantities.com/api/v1/calculators/loft-conversion-cost-calculator.json" } ], "confusions": [ { "question": "Does a loft conversion mean the same thing everywhere?", "answer": "No, and the two meanings describe completely different projects. In Britain and Australia, converting the loft means making a habitable room in the roof space of an existing house: adding a stair, strengthening or replacing the floor, insulating at the roof slope, adding windows or dormers, and meeting fire escape and headroom requirements. In North America, a loft apartment means a dwelling made from an industrial or commercial floor plate, and a loft within a dwelling usually means an open mezzanine overlooking a room below. So a British article about loft conversions and an American one about loft living have almost nothing in common beyond the word." }, { "question": "Why does insulating at the ceiling or at the slope change everything?", "answer": "Because it decides which side of the thermal envelope the roof space is on, and therefore how it must be ventilated. Insulate at the ceiling and the roof space is OUTSIDE the envelope: it is cold, it needs ventilating so moisture leaking up from the house can escape rather than condensing on the underside of the roof, and anything stored there is in an unheated space. Insulate at the slope and the space is INSIDE: it is warm, it is part of the heated volume, and the ventilation strategy changes completely — either a ventilated cavity above the insulation or a designed unventilated warm-roof build-up. Converting a loft moves the insulation line, which is why a conversion that adds insulation at the slope without removing it from the ceiling creates a cold pocket in between." }, { "question": "What usually stops a roof space becoming a room?", "answer": "Headroom, the floor, and the escape route, roughly in that order. The existing ceiling joists are sized to carry a ceiling and light storage rather than a floor and its occupants, so they are normally strengthened or replaced — which eats headroom from below. A trussed roof has webs through the middle of the space that cannot simply be cut, so a conversion means a structural alteration rather than a fit-out. And a habitable room in a roof brings fire requirements: a protected escape route, often the whole stair enclosure upgraded, and window or means-of-escape provision. Each of those is normal and costed, and each is why the space that looks empty is not simply available." } ], "related": [ "joist" ] }, { "slug": "mortar-designation", "concept": "Mortar designations", "family": "materials", "definition": "How a masonry mortar's strength and composition are specified. Each market uses its own lettering or numbering system, and the labels are not translations of each other.", "url": "https://craftquantities.com/glossary/mortar-designation/", "names": [ { "market": "US", "term": "Type N / S / M / O", "alsoCalled": [ "Type S mortar", "ASTM mortar types" ], "exactness": "false-friend", "note": "Letters name a proportion and a strength, with M the strongest and O the weakest. \"Type M\" has nothing to do with a European M-class number." }, { "market": "CA", "term": "Type N / S / M / O", "alsoCalled": [ "CSA mortar types" ], "exactness": "false-friend", "note": "The same letters as the United States, specified to the Canadian standard — so the letter is familiar and the governing document is not the same one." }, { "market": "UK", "term": "M-class (M2, M4, M6, M12)", "alsoCalled": [ "designation (i) to (iv)", "mortar class" ], "exactness": "false-friend", "note": "The M number is the compressive strength in N/mm², NOT a letter grade — and the older British designations (i) to (iv) run the opposite way, with (i) the strongest." }, { "market": "AU", "term": "M1 to M4", "alsoCalled": [ "mortar class" ], "exactness": "false-friend", "note": "Australian classes run M1 to M4 with M4 the strongest, which is a different numbering again from both the European strength classes and the American letters." } ], "standards": [ { "market": "US", "standard": "ASTM C270", "covers": "Mortar for unit masonry — the Type N/S/M/O specification." }, { "market": "UK", "standard": "BS EN 998-2", "covers": "Masonry mortar — including the M-class strength designation." }, { "market": "AU", "standard": "AS 3700", "covers": "Masonry structures, including mortar classes." } ], "calculators": [ { "slug": "stone-veneer-mortar-calculator", "json": "https://craftquantities.com/api/v1/calculators/stone-veneer-mortar-calculator.json" }, { "slug": "mortar-cubic-yards-to-tons-calculator", "json": "https://craftquantities.com/api/v1/calculators/mortar-cubic-yards-to-tons-calculator.json" }, { "slug": "cmu-block-grout-calculator", "json": "https://craftquantities.com/api/v1/calculators/cmu-block-grout-calculator.json" } ], "confusions": [ { "question": "Is Type M mortar the same as M4 mortar?", "answer": "No, and the collision is close to the worst possible one, because both look like a strength grade and they come from unrelated systems. American Type M is a letter naming a mix proportion and a minimum compressive strength, and it is the strongest of the four letters. A British or European M4 is a strength CLASS whose number is the compressive strength in newtons per square millimetre, so the number is the property directly. A specification reading \"Type M\" and one reading \"M4\" are written in different languages, and picking a mortar by matching the letter M gets a considerably stronger mortar than intended — which, counter-intuitively, is usually the wrong direction." }, { "question": "Why is a stronger mortar not automatically better?", "answer": "Because the mortar is meant to be weaker than the units it joins, and a mortar that is too strong moves the failure. Masonry moves — thermally, with moisture, with settlement — and a comparatively weak mortar accommodates that movement by cracking in the joints, where cracks are fine, distributed and repointable. A mortar stronger than the brick concentrates the movement into the units instead, so the cracks run through the bricks and the wall is no longer repairable by raking out and repointing. That is why specifications call for the weakest mortar consistent with the exposure and the loading, why lime mortars are specified for older soft masonry, and why repointing in a strong cement mortar damages historic brickwork." }, { "question": "How do the older British designations relate to the M-classes?", "answer": "They run in the opposite direction, which is a second trap in the same field. The older British designations (i), (ii), (iii) and (iv) number the mixes with (i) the STRONGEST and (iv) the weakest, so the number rises as the strength falls. The European M-classes number by strength in N/mm², so the number rises as the strength rises. Both appear in British documents — older specifications and many trade references still use the designations, and current standards use the classes — so a document mixing them is not unusual and reading a number without knowing which system it belongs to inverts the intent. The correct approach is to read the mix proportions or the stated strength rather than the label." } ], "related": [ "cement", "pointing" ] }, { "slug": "stopcock", "concept": "Stopcock / shut-off valve", "family": "services", "definition": "The valve that isolates a building's incoming water supply. There are normally two — one at the boundary belonging to the supplier, and one inside the building belonging to the occupier.", "url": "https://craftquantities.com/glossary/stopcock/", "names": [ { "market": "UK", "term": "stopcock", "alsoCalled": [ "stop tap", "internal stop valve", "external stopcock" ], "exactness": "close", "note": "\"Stopcock\" names both the supplier's valve at the boundary and the occupier's inside the building, so the word alone does not say which — and only one of them is yours to operate." }, { "market": "AU", "term": "stop tap", "alsoCalled": [ "water meter valve", "isolation valve" ], "exactness": "close", "note": "Australian practice usually pairs the boundary valve with the water meter, so the outdoor isolation point is commonly described by the meter rather than by the valve." }, { "market": "US", "term": "shut-off valve", "alsoCalled": [ "main shut-off", "curb stop", "water meter valve" ], "exactness": "close", "note": "The boundary valve is a \"curb stop\", operated by the utility with a key — a specific term with no British equivalent word, though the British external stopcock is the same idea." }, { "market": "CA", "term": "shut-off valve", "alsoCalled": [ "main shut-off", "curb stop" ], "exactness": "close", "note": "As the United States, with the curb stop normally the utility's to operate and freezing depth driving how deep the boundary chamber sits." } ], "standards": [ { "market": "UK", "standard": "Water Supply (Water Fittings) Regulations", "covers": "Requirements for fittings, including isolation and backflow prevention." }, { "market": "US", "standard": "IPC / UPC", "covers": "Water service and distribution requirements, including shut-off provision." } ], "calculators": [ { "slug": "domestic-water-pipe-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/domestic-water-pipe-sizing-calculator.json" }, { "slug": "water-meter-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/water-meter-sizing-calculator.json" }, { "slug": "circulator-pump-head-loss-calculator", "json": "https://craftquantities.com/api/v1/calculators/circulator-pump-head-loss-calculator.json" } ], "confusions": [ { "question": "Which valve is mine to turn off?", "answer": "The internal one, almost always — and knowing which is which before there is water on the floor is the point of the distinction. A building normally has two isolation points: one at or near the boundary, in a chamber under the footway or the drive, which belongs to the water undertaker and is often operated with a long key; and one inside, usually where the supply first enters, which is the occupier's. Turning the internal valve isolates the building. The boundary valve is the supplier's, may serve more than one property, and in some jurisdictions operating it without authority is an offence — so the practical advice is to find and label the internal one, and to check it actually turns before it is needed." }, { "question": "Why does an old stopcock often refuse to turn?", "answer": "Because it has not been moved in years and its working parts have seized or bonded. A valve left in one position for a long time collects scale and corrosion around the spindle and the seat, and the washer can adhere to the seating; forcing it then either shears the spindle or tears the washer, so a valve that will not turn becomes a valve that will not seal. The standard advice is to exercise the valve periodically — a full close and open once or twice a year — which keeps it free and reveals the failure at a convenient moment rather than an inconvenient one. It is also why plumbers routinely fit a new isolation valve when working on an old supply rather than trusting the existing one." }, { "question": "What is a service valve, and is it the same thing?", "answer": "No — service or isolation valves are the small local valves fitted at individual fittings and appliances, so that a tap, a cistern or a washing machine can be worked on without shutting the whole building down. They are a different scale of device from the main stop valve and they are not a substitute for it: a building with isolation valves everywhere still needs one point that stops the supply entirely. The related distinction is the drain-down provision — a drain cock at the low point that empties the system once it is isolated, which is what actually lets pipework be opened. Isolating without draining leaves the standing water in the pipe to arrive on the floor." } ], "related": [ "soil-pipe", "hot-water-cylinder", "rising-main" ] }, { "slug": "cavity-wall", "concept": "Cavity wall / drainage cavity", "family": "envelope", "definition": "A wall built in two leaves with a deliberate gap between them, so that water crossing the outer leaf runs down the cavity and out rather than reaching the inner one.", "url": "https://craftquantities.com/glossary/cavity-wall/", "names": [ { "market": "UK", "term": "cavity wall", "alsoCalled": [ "twin-leaf wall", "cavity" ], "exactness": "close", "note": "Names a whole wall TYPE — two masonry leaves tied together — which has been the default British external wall for a century, not a detail within another assembly." }, { "market": "AU", "term": "cavity wall", "alsoCalled": [ "brick veneer cavity", "cavity" ], "exactness": "close", "note": "Used for both the twin-masonry wall and the gap behind a brick veneer on a framed wall, so the phrase covers two quite different constructions." }, { "market": "US", "term": "drainage cavity", "alsoCalled": [ "air space", "brick veneer cavity", "rainscreen gap" ], "exactness": "close", "note": "The gap behind a masonry veneer over a framed and sheathed wall. The structure is the frame, not the outer leaf, which is the opposite arrangement from a British cavity wall." }, { "market": "CA", "term": "drainage cavity", "alsoCalled": [ "air space", "rainscreen gap" ], "exactness": "close", "note": "As the United States, with the cavity width and the drainage provisions set by the Canadian code and by climate zone rather than by the British convention." } ], "standards": [ { "market": "UK", "standard": "BS EN 1996 / Approved Document C", "covers": "Masonry design, and resistance to moisture from the ground and weather." }, { "market": "US", "standard": "TMS 402 / ASTM C1063", "covers": "Masonry structures and veneer anchorage requirements." } ], "calculators": [ { "slug": "wall-tie-density-calculator", "json": "https://craftquantities.com/api/v1/calculators/wall-tie-density-calculator.json" }, { "slug": "cavity-wall-weep-hole-calculator", "json": "https://craftquantities.com/api/v1/calculators/cavity-wall-weep-hole-calculator.json" }, { "slug": "brick-calculator", "json": "https://craftquantities.com/api/v1/calculators/brick-calculator.json" } ], "confusions": [ { "question": "Is a cavity wall the same as a brick veneer wall?", "answer": "They share the cavity and differ in what holds the building up. A British cavity wall is two masonry leaves — traditionally brick outside and block inside — tied together, with the INNER leaf carrying the floor and roof loads. A North American brick veneer wall is a timber or steel frame, sheathed and weather-barriered, with a single leaf of brick hung outside it on ties; the frame carries everything and the brick carries only itself. So the outer leaf looks the same from the street and does a completely different structural job, which changes the ties, the movement provisions, the support at openings and what happens if the veneer is removed." }, { "question": "What are the ties actually for?", "answer": "Transferring wind load between the leaves while letting them move independently, and they are the component most often got wrong. A tie has to be stiff enough in compression and tension to carry wind pressure and suction from the outer leaf into the structure, and free enough to allow the differential movement between two leaves of different materials at different temperatures and moisture contents. It also has to shed water: a tie sloping the wrong way, or one with mortar droppings bridging it, carries water across the cavity to the inner leaf, which is the commonest single cause of damp in a cavity wall. Their type, spacing and embedment are specified, and around openings and at edges the spacing tightens." }, { "question": "Does filling the cavity with insulation defeat it?", "answer": "It changes the wall from a drained cavity to a filled one, which is a different construction with different rules rather than a simple upgrade. A clear cavity works by letting water run down an open gap and out through weeps; a full-fill insulation has to be a material and an installation approved for that use, which resists water transfer across itself rather than relying on an air gap. Partial fill keeps a residual clear cavity of a specified width, which is why board insulation is held against the inner leaf rather than filling the gap. Retrofitting full fill into a wall built as a drained cavity — particularly in a severely exposed location, or where the outer leaf is cracked or the ties are already bridged — is how a dry wall becomes a damp one." } ], "related": [ "dpc", "breeze-block", "wall-tie", "trickle-vent", "weep-hole", "party-wall" ] }, { "slug": "hot-water-cylinder", "concept": "Hot water cylinder / water heater", "family": "services", "definition": "The vessel storing heated water for taps and showers. How it is fed, how it is heated and how its pressure is controlled differ enough between markets that the words carry an assumed system with them.", "url": "https://craftquantities.com/glossary/hot-water-cylinder/", "names": [ { "market": "UK", "term": "hot water cylinder", "alsoCalled": [ "cylinder", "unvented cylinder", "calorifier" ], "exactness": "false-friend", "note": "A \"tank\" in British usage is the COLD storage cistern, usually in the loft — so \"hot water tank\" reads as a category error rather than a synonym for the cylinder." }, { "market": "AU", "term": "hot water unit", "alsoCalled": [ "HWS", "hot water service", "cylinder" ], "exactness": "close", "note": "Australian usage names the whole SERVICE rather than the vessel, and the unit is commonly outdoors — a siting difference that changes the pipe runs and the losses." }, { "market": "US", "term": "water heater", "alsoCalled": [ "hot water tank", "tank water heater" ], "exactness": "false-friend", "note": "Names a vessel that HEATS as well as stores, usually directly fired or electric. The British cylinder is more often heated indirectly by a boiler through a coil." }, { "market": "CA", "term": "water heater", "alsoCalled": [ "hot water tank" ], "exactness": "false-friend", "note": "As the United States, and commonly rented from the utility rather than owned — which has no British or Australian equivalent and changes who replaces it." } ], "standards": [ { "market": "UK", "standard": "Approved Document G / BS EN 12897", "covers": "Hot water safety, and unvented storage water heater requirements." }, { "market": "US", "standard": "ASHRAE 90.1 / IPC", "covers": "Water heating equipment efficiency and installation requirements." } ], "calculators": [ { "slug": "water-heater-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/water-heater-sizing-calculator.json" }, { "slug": "water-heater-recovery-time-calculator", "json": "https://craftquantities.com/api/v1/calculators/water-heater-recovery-time-calculator.json" }, { "slug": "expansion-tank-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/expansion-tank-sizing-calculator.json" } ], "confusions": [ { "question": "Is a hot water tank the same as a cylinder?", "answer": "The words point at the same job and carry different assumptions, and in British usage \"tank\" points somewhere else entirely. A traditional British system has a cold water storage TANK — an open cistern in the loft — feeding a hot water CYLINDER lower down, with the height difference providing the pressure. So a British plumber hearing \"hot water tank\" reaches for a clarification rather than a spanner. American usage has no equivalent loft cistern in most housing, the supply is mains-pressure throughout, and the storage vessel is a tank that heats its own contents. Both deliver hot water; they are different system architectures with different failure modes and different components." }, { "question": "What is the difference between vented and unvented?", "answer": "Where the pressure comes from and what contains it, and it is the distinction with the most safety weight. A vented cylinder is fed from an open cistern above it and is open to atmosphere, so it cannot be pressurised and its flow depends on the height of the cistern. An unvented cylinder is fed directly from the main, sealed, and therefore contains mains pressure and the expansion of heated water — which is why it requires an expansion vessel or air gap, a pressure relief arrangement and a temperature relief device, and why installing or servicing one is a competence-restricted activity in several jurisdictions. A sealed vessel with a failed relief path is a genuine hazard, not merely a leak." }, { "question": "Why does an expansion vessel exist at all?", "answer": "Because water expands when heated and a sealed system has nowhere to put the extra volume. In an open vented system the expansion simply pushes water back up toward the cistern, which is why no vessel is needed. Seal the system — an unvented cylinder, or a pressurised heating circuit — and the same expansion has to be absorbed somewhere, or the pressure rises until a relief device opens and discharges. An expansion vessel gives it a compressible gas cushion behind a diaphragm to push into. Its size follows from the system volume and the temperature rise, and the commonest fault is not a failed vessel but a lost gas charge, which lets the diaphragm bottom out and the pressure spike on every heating cycle." } ], "related": [ "stopcock", "immersion-heater", "combi-boiler", "radiator", "cistern", "pipe-insulation" ] }, { "slug": "joist", "concept": "Joist, rafter and centres", "family": "structure", "definition": "The repeating horizontal or sloping members that carry a floor or a roof, and the spacing between them — which is set by a module the sheet materials are made to suit rather than chosen freely.", "url": "https://craftquantities.com/glossary/joist/", "names": [ { "market": "US", "term": "joist", "alsoCalled": [ "rafter", "on center (o.c.)", "16 o.c." ], "exactness": "false-friend", "note": "The member names match, but spacing is stated in INCHES on centre — 16 or 24 — and sheet goods are made in feet to suit, so the whole module differs from the metric one." }, { "market": "CA", "term": "joist", "alsoCalled": [ "rafter", "on centre" ], "exactness": "false-friend", "note": "American spacing conventions with metric documentation, so drawings commonly state both — and the two do not divide into each other evenly." }, { "market": "UK", "term": "joist", "alsoCalled": [ "rafter", "centres", "400 centres" ], "exactness": "false-friend", "note": "Spacing is stated in MILLIMETRES between centres — 400 or 600 — and boards are 1200 or 2400 mm to suit. A detail drawn for 16 inch centres does not land on 400 mm." }, { "market": "AU", "term": "joist", "alsoCalled": [ "rafter", "centres", "batten spacing" ], "exactness": "false-friend", "note": "Metric centres as the UK, though the standard spacings and the sheet sizes differ from British ones in places, so neither converts cleanly to the other." } ], "standards": [ { "market": "US", "standard": "IRC / NDS", "covers": "Span tables and design values for repetitive framing members." }, { "market": "UK", "standard": "BS EN 1995 (Eurocode 5)", "covers": "Design of timber structures, including floor and roof members." }, { "market": "AU", "standard": "AS 1684", "covers": "Residential timber-framed construction, including span tables." } ], "calculators": [ { "slug": "deck-joist-span-calculator", "json": "https://craftquantities.com/api/v1/calculators/deck-joist-span-calculator.json" }, { "slug": "common-rafter-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/common-rafter-length-calculator.json" }, { "slug": "lumber-dimensional-size-calculator", "json": "https://craftquantities.com/api/v1/calculators/lumber-dimensional-size-calculator.json" }, { "slug": "floor-vibration-frequency-calculator", "json": "https://craftquantities.com/api/v1/calculators/floor-vibration-frequency-calculator.json" } ], "confusions": [ { "question": "Why does the spacing module matter more than the number?", "answer": "Because everything sheet-shaped on a building is manufactured to land on it. Boards, plasterboard, sheathing, insulation batts and plasterboard ceilings are all made in widths that divide evenly by the local spacing — four feet by sixteen or twenty-four inches in North America, 1200 mm by 400 or 600 mm in Britain and Australia. Change the spacing and every sheet has to be cut, every joint lands mid-member or off it, and insulation batts either compress or leave gaps. That is why converting a detail between markets is not a matter of finding the nearest spacing: the whole set of materials above it is dimensioned to the module you left behind." }, { "question": "Are span tables interchangeable between markets?", "answer": "No, and the reasons compound. The member sizes differ, because a nominal 2x4 has no metric equivalent. The grading systems differ, so the design strength assigned to an apparently similar piece is not the same number. The load cases differ, because each market's code sets its own imposed loads for a domestic floor. And the deflection limits differ. A span table is the output of all four decisions, so reading a span off one market's table and building to another market's materials is not a conversion — it is using the wrong design. Where a member has to be sized across markets, it is sized from that market's table and materials, or by an engineer." }, { "question": "What is the difference between a rafter and a truss?", "answer": "How the roof's forces are resolved, and therefore what may be done with the space. A rafter is a single member spanning from wall plate to ridge, so the roof's spread is resisted by ceiling ties, purlins and the walls — which leaves the loft as usable or convertible space. A truss is a prefabricated triangulated frame in which the webs carry the forces internally, so it needs no intermediate support and gives a clear span, but the webs occupy the roof space and cannot be cut or altered without a designed intervention. That distinction is what decides whether a loft conversion is a fit-out or a structural alteration, and it is visible at a glance once you know to look for the webs." } ], "related": [ "nominal-size", "loft", "wall-plate", "noggin", "suspended-floor", "decking" ] }, { "slug": "r-value", "concept": "R-value and U-value", "family": "measurement", "definition": "Two ways of stating how well a construction resists heat flow. R is RESISTANCE and higher is better; U is TRANSMITTANCE and lower is better. They are reciprocals of each other, so a figure read as the wrong one is not merely off — it is inverted.", "url": "https://craftquantities.com/glossary/r-value/", "names": [ { "market": "US", "term": "R-value", "alsoCalled": [ "R-13", "R-30" ], "exactness": "false-friend", "note": "The bare R number is in IMPERIAL units. The same construction stated in metric RSI carries a number roughly five and a half times smaller, with the same letter on it." }, { "market": "CA", "term": "RSI", "alsoCalled": [ "R-value", "metric R" ], "exactness": "false-friend", "note": "Canada uses metric RSI in codes while products are commonly labelled with the American R, so both numbers appear on the same job meaning the same performance." }, { "market": "UK", "term": "U-value", "alsoCalled": [ "thermal transmittance", "R-value (materials)" ], "exactness": "false-friend", "note": "British practice specifies elements by U-value, where LOWER is better — the opposite direction from R. R appears for individual materials, not for the element." }, { "market": "AU", "term": "R-value", "alsoCalled": [ "total R-value", "U-value" ], "exactness": "false-friend", "note": "Australia uses metric R for insulation and elements, so an Australian R number is not comparable with an American one despite the identical letter." } ], "standards": [ { "market": "US", "standard": "ASHRAE 90.1 / IECC", "covers": "Prescriptive R-value and assembly U-factor requirements by climate zone." }, { "market": "UK", "standard": "Approved Document L / BS EN ISO 6946", "covers": "Element U-value limits, and the method for calculating them." }, { "market": "AU", "standard": "NCC Section J / AS/NZS 4859", "covers": "Total R-value requirements and the rating of insulation materials." } ], "calculators": [ { "slug": "r-value-to-u-value-calculator", "json": "https://craftquantities.com/api/v1/calculators/r-value-to-u-value-calculator.json" }, { "slug": "rsi-to-r-value-calculator", "json": "https://craftquantities.com/api/v1/calculators/rsi-to-r-value-calculator.json" }, { "slug": "insulation-batt-calculator", "json": "https://craftquantities.com/api/v1/calculators/insulation-batt-calculator.json" }, { "slug": "r-value-to-rsi-calculator", "json": "https://craftquantities.com/api/v1/calculators/r-value-to-rsi-calculator.json" }, { "slug": "climate-zone-insulation-calculator", "json": "https://craftquantities.com/api/v1/calculators/climate-zone-insulation-calculator.json" } ], "confusions": [ { "question": "Is a higher number better or worse?", "answer": "It depends which letter is in front of it, and getting that backwards inverts every comparison. R is RESISTANCE: it measures how much a construction opposes heat flow, so a higher R is a better-insulated element. U is TRANSMITTANCE: it measures how much heat passes, so a lower U is better. They are reciprocals — one divided by the other — so the two describe the same physics from opposite ends. A reader comparing an American product quoting R against a British specification quoting U is comparing numbers that move in opposite directions, and choosing the larger figure in both cases will pick the best insulation in one market and the worst in the other." }, { "question": "Why is an American R-value so much larger than an Australian one?", "answer": "Because they are different units wearing the same letter. The American R is in imperial units — hour, square foot, degree Fahrenheit per BTU — and the metric R or RSI used in Canada, Australia and Europe is in square metre kelvin per watt. The conversion factor between them is a little over five and a half, so a product labelled R-19 in the United States is roughly R-3.3 in metric terms, and neither number is wrong. Product literature often states only one. That is why an insulation comparison across markets has to establish the UNIT before comparing the figures, and why a specification calling for R-4 means something very different depending on where it was written." }, { "question": "Why does the assembly's figure differ from the insulation's?", "answer": "Because the insulation is only one layer, and the studs, joists and fixings running through it are not insulation. A wall's actual performance is a weighted result across the whole element, including the framing that bridges the insulation — which is why an element built with R-19 batts does not achieve R-19, and why the gap widens as the framing gets denser. Codes handle this in different ways: some set a prescriptive value for the insulation, some require a calculated whole-element figure, and some allow either. The practical consequence is that a specification naming an insulation product has not specified the wall's performance, and a reader comparing a nominal insulation figure with a calculated assembly figure is comparing two different quantities." } ], "related": [ "insulation-batt", "thermal-bridge" ] }, { "slug": "wall-plate", "concept": "Wall plate, top plate and sole plate", "family": "structure", "definition": "The horizontal timbers at the top and bottom of a wall that spread load and give the studs, joists or rafters something to fix to. Which one an unqualified 'plate' means depends on the market and on the construction.", "url": "https://craftquantities.com/glossary/wall-plate/", "names": [ { "market": "UK", "term": "wall plate", "alsoCalled": [ "sole plate", "head plate" ], "exactness": "false-friend", "note": "In masonry construction a wall plate is the timber bedded on TOP of the wall that rafters and joists sit on — not the top of a stud wall, which is the American sense." }, { "market": "AU", "term": "top plate", "alsoCalled": [ "wall plate", "bottom plate" ], "exactness": "close", "note": "Australian framing usage follows the American top/bottom plate convention, while wall plate survives for the member on masonry — so both senses are in use." }, { "market": "US", "term": "top plate", "alsoCalled": [ "double top plate", "sole plate", "bottom plate", "sill plate" ], "exactness": "false-friend", "note": "Names the member at the top of a STUD WALL, commonly doubled. The bottom one is the sole or bottom plate, and the treated member on a foundation is the sill plate." }, { "market": "CA", "term": "top plate", "alsoCalled": [ "sill plate", "bottom plate" ], "exactness": "false-friend", "note": "As the United States, with sill plate the anchored member on the foundation — a word that also means the bottom of a window opening, in the same set of drawings." } ], "standards": [ { "market": "US", "standard": "IRC Chapter 6", "covers": "Wall construction, including plate sizes, splices and anchorage." }, { "market": "UK", "standard": "BS 8103 / Approved Document A", "covers": "Structural design of low-rise housing, including wall plate bedding and strapping." } ], "calculators": [ { "slug": "framing-stud-calculator", "json": "https://craftquantities.com/api/v1/calculators/framing-stud-calculator.json" }, { "slug": "lumber-dimensional-size-calculator", "json": "https://craftquantities.com/api/v1/calculators/lumber-dimensional-size-calculator.json" }, { "slug": "common-rafter-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/common-rafter-length-calculator.json" } ], "confusions": [ { "question": "Which member does an unqualified 'plate' mean?", "answer": "It depends on what the wall is made of and who wrote the drawing. In British masonry construction, the wall plate is the timber bedded along the top of a masonry wall, strapped down, on which the rafters and ceiling joists bear — so it is the interface between the masonry and the roof. In North American light-frame construction, the plates are the horizontal members of the stud wall itself: a top plate, usually doubled so that joints in the two layers are staggered, and a bottom or sole plate the studs stand on. The two conventions describe different members in different positions, and a detail that says only 'plate' is ambiguous the moment it crosses a border." }, { "question": "Why is the top plate doubled in North American framing?", "answer": "Because it does two jobs that a single member does poorly. It carries and distributes the load from joists or trusses above, which may not land over studs; and it ties the wall together in its length, which matters at corners, at intersections and across openings. Doubling it lets the joints in the two layers be staggered and lapped at corners and partitions, so the plate is continuous even though no single piece of timber is. British masonry practice achieves the equivalent differently, with a single wall plate lapped at joints and strapped down to the masonry at intervals — the restraint comes from the strapping rather than from a second layer." }, { "question": "What does 'sill' mean here, and why is it confusing?", "answer": "Two unrelated things that appear in the same set of drawings. In North American framing, a sill plate is the timber bolted to the top of a foundation wall, usually treated because it is in contact with masonry, on which the floor structure sits. In every market, a sill is also the horizontal member at the BOTTOM of a window or door opening — a completely different component with a completely different job, and the one most readers think of first. A drawing note about the sill is therefore ambiguous unless it says which, and the ambiguity is worst in exactly the documents that mix structural and joinery information." } ], "related": [ "joist", "purlin" ] }, { "slug": "sand", "concept": "Sand grades", "family": "materials", "definition": "Fine aggregate, named by completely different logics in different markets: British and Australian names describe the intended USE, and American designations describe the GRADING. Neither translates to the other without going through the property.", "url": "https://craftquantities.com/glossary/sand/", "names": [ { "market": "UK", "term": "sharp sand", "alsoCalled": [ "building sand", "soft sand", "plastering sand", "grit sand" ], "exactness": "false-friend", "note": "Names describe the USE and by implication the particle shape: sharp is angular and coarse for concrete and screeds, soft or building sand is finer and rounder for mortar and rendering." }, { "market": "AU", "term": "sharp sand", "alsoCalled": [ "brickies sand", "washed sand", "fatty sand" ], "exactness": "false-friend", "note": "As the UK, use-based names, with local trade words — brickies sand is the mortar sand and is chosen for workability rather than strength." }, { "market": "US", "term": "concrete sand", "alsoCalled": [ "masonry sand", "C-33 sand", "mason sand", "play sand" ], "exactness": "false-friend", "note": "Designations reference a GRADING specification rather than a use, so the same product name means a particle size distribution, not a job it suits." }, { "market": "CA", "term": "concrete sand", "alsoCalled": [ "masonry sand", "bedding sand" ], "exactness": "false-friend", "note": "As the United States in naming, with provincial specifications setting the gradings — so the designation identifies a spec rather than a product available everywhere." } ], "standards": [ { "market": "US", "standard": "ASTM C33", "covers": "Concrete aggregates, including the grading limits for fine aggregate." }, { "market": "UK", "standard": "BS EN 12620 / BS EN 13139", "covers": "Aggregates for concrete, and aggregates for mortar." } ], "calculators": [ { "slug": "sand-cubic-yards-to-tons-calculator", "json": "https://craftquantities.com/api/v1/calculators/sand-cubic-yards-to-tons-calculator.json" }, { "slug": "concrete-mix-ratio-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-mix-ratio-calculator.json" }, { "slug": "mortar-cubic-yards-to-tons-calculator", "json": "https://craftquantities.com/api/v1/calculators/mortar-cubic-yards-to-tons-calculator.json" } ], "confusions": [ { "question": "What is the difference between sharp sand and building sand?", "answer": "Particle shape and grading, and therefore what each is good at. Sharp sand is coarser and more angular, so its particles interlock and it produces a stronger, less workable mix — which is why it goes into concrete, screeds and bedding. Building or soft sand is finer and its particles are rounder, which makes a mortar that spreads and holds its shape on a trowel; the same properties make it a poor choice for concrete, because the mix is weaker and needs more water. Using one where the other belongs is a real error rather than a preference: soft sand in a screed gives a weak, dusty floor, and sharp sand in mortar gives a mix a bricklayer cannot work with." }, { "question": "Why can I not just look up the American equivalent?", "answer": "Because the two naming systems answer different questions. A British name tells you what the sand is FOR and leaves you to infer the grading; an American designation tells you the GRADING and leaves you to decide the use. So there is no dictionary entry that maps sharp sand to a single American product — the honest route is to read through the name to the property. Establish what the specification actually needs (coarse and angular, or fine and rounded, and within what grading envelope), then find the local product that meets it. That is the same approach that applies to sub-base designations and mortar classes, and for the same reason." }, { "question": "Does washed or unwashed matter?", "answer": "Substantially, and it is a property neither naming system puts in the name. Unwashed sand carries fines, silt and clay, which increase the water demand of a mix and reduce its strength, and in a concrete they can interfere with the bond between the paste and the aggregate. Washed sand has had those removed. For mortar a small clay content is sometimes tolerated or even valued for workability; for concrete and screed it is a defect, which is why specifications reference a grading standard that limits it rather than naming a product. Where a bulk delivery looks dusty or stains the hand, that is the fines showing, and it is worth establishing what was actually supplied before it goes into a structural mix." } ], "related": [ "cement", "hardcore", "aggregate-size" ] }, { "slug": "slump", "concept": "Slump and consistence", "family": "materials", "definition": "How workable fresh concrete is — how far a moulded cone of it subsides when the mould is lifted. American practice states a measured distance, European practice states a CLASS covering a range, and the two are not the same kind of number.", "url": "https://craftquantities.com/glossary/slump/", "names": [ { "market": "US", "term": "slump", "alsoCalled": [ "4 inch slump", "slump test" ], "exactness": "false-friend", "note": "A measured distance in INCHES, quoted as a target with a tolerance — a point value rather than a band." }, { "market": "CA", "term": "slump", "alsoCalled": [ "slump in mm" ], "exactness": "false-friend", "note": "The same test stated in millimetres, so a Canadian slump figure and an American one describe the same measurement in different units." }, { "market": "UK", "term": "consistence class", "alsoCalled": [ "S1 to S5", "slump class", "slump in mm" ], "exactness": "false-friend", "note": "An S-class is a BAND of slump values, not a measurement — so S3 covers a range and cannot be converted to a single figure." }, { "market": "AU", "term": "slump", "alsoCalled": [ "slump in mm" ], "exactness": "close", "note": "Measured in millimetres as a value rather than a class, so Australian practice is closer to the North American convention than to the European one." } ], "standards": [ { "market": "US", "standard": "ASTM C143", "covers": "Slump of hydraulic-cement concrete — the test method." }, { "market": "UK", "standard": "BS EN 12350-2 / BS EN 206", "covers": "Slump test method, and the consistence classes concrete is specified by." } ], "calculators": [ { "slug": "concrete-mix-ratio-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-mix-ratio-calculator.json" }, { "slug": "concrete-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-calculator.json" }, { "slug": "aci-211-water-cement-ratio-calculator", "json": "https://craftquantities.com/api/v1/calculators/aci-211-water-cement-ratio-calculator.json" } ], "confusions": [ { "question": "Can I convert an S-class to a slump figure?", "answer": "Not to a single figure, because they are different kinds of quantity. A slump specified in inches or millimetres is a target value with a tolerance around it, so the concrete is accepted if it measures within that tolerance. A European consistence class such as S2 or S3 is a BAND: any slump inside the class's range conforms, and two loads at opposite ends of the same class behave noticeably differently on site. So an S-class maps to a range rather than a number, and a specification that converts a class to a single figure has narrowed it — which may be what was wanted, but it is a change to the specification rather than a translation of it." }, { "question": "Does a higher slump mean weaker concrete?", "answer": "Not by itself, and this is the more damaging confusion. Slump measures workability, not strength. A mix can be made wetter by adding water, which does reduce strength because it raises the water-cement ratio — and that is where the association comes from. But it can also be made more workable by a plasticiser or superplasticiser at the same water content, which raises the slump and leaves the strength alone or improves it. So a high-slump mix arriving on site is not evidence of a weak one. What IS evidence of a weak one is water added at the site after batching, which is why specifications prohibit it and why the delivery ticket matters." }, { "question": "Why is the slump measured at all?", "answer": "Because it is the only property of fresh concrete that can be checked in two minutes at the point of delivery, and because consistency between loads matters as much as the value. A load that arrives noticeably different from the last one indicates something changed at the plant or in transit, and that is worth knowing before it is placed. The test is also a conformity check: the concrete was specified at a consistence, and this is how the site establishes that what arrived matches. It says nothing about strength, which is established by cubes or cylinders tested later — so a load can pass the slump test and fail at twenty-eight days, and the two tests are not substitutes." } ], "related": [ "cement", "formwork", "concrete-grade", "concrete-placing" ] }, { "slug": "aggregate-size", "concept": "Aggregate size designations", "family": "materials", "definition": "How the stone in concrete and sub-base is specified. European practice gives a size range in millimetres; North American practice gives a NUMBER that indexes a grading envelope. The number is not a dimension.", "url": "https://craftquantities.com/glossary/aggregate-size/", "names": [ { "market": "UK", "term": "20 mm aggregate", "alsoCalled": [ "4/20", "single size", "graded aggregate" ], "exactness": "false-friend", "note": "Stated as a size range — the lower and upper sieve sizes — so 4/20 means the material passes 20 mm and is retained on 4 mm. The numbers ARE dimensions." }, { "market": "AU", "term": "20 mm aggregate", "alsoCalled": [ "nominal size", "graded aggregate" ], "exactness": "close", "note": "Metric nominal sizes as the UK, with Australian standard gradings — so the convention matches even where the specific envelopes do not." }, { "market": "US", "term": "#57 stone", "alsoCalled": [ "No. 57", "#8", "#4", "size number" ], "exactness": "false-friend", "note": "The number indexes a GRADING TABLE, not a size. A #57 is not 57 of anything — it names an envelope of sieve percentages." }, { "market": "CA", "term": "size number", "alsoCalled": [ "#57 stone", "clear stone", "20 mm clear" ], "exactness": "false-friend", "note": "Both conventions in use — American size numbers alongside metric descriptions — so a Canadian specification may carry either and they are not interchangeable." } ], "standards": [ { "market": "US", "standard": "ASTM C33 / AASHTO M43", "covers": "Standard sizes of coarse aggregate, defined as grading envelopes by size number." }, { "market": "UK", "standard": "BS EN 12620", "covers": "Aggregates for concrete, designated by lower and upper sieve size." } ], "calculators": [ { "slug": "gravel-cubic-yards-to-tons-calculator", "json": "https://craftquantities.com/api/v1/calculators/gravel-cubic-yards-to-tons-calculator.json" }, { "slug": "aggregate-fineness-modulus-calculator", "json": "https://craftquantities.com/api/v1/calculators/aggregate-fineness-modulus-calculator.json" }, { "slug": "concrete-mix-ratio-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-mix-ratio-calculator.json" } ], "confusions": [ { "question": "What does the number in #57 stone mean?", "answer": "It is an index, not a measurement. American and Canadian coarse aggregate is specified by a SIZE NUMBER that refers to a row in a standard grading table, and that row gives the percentage passing each of a series of sieves. So a #57 is defined by a distribution of particle sizes rather than by a single dimension, and the number itself carries no length. That is the opposite of the European convention, where a designation such as 4/20 states the lower and upper sieve sizes directly and the numbers are millimetres. Reading a size number as though it were a dimension, or converting it as though it had units, produces nonsense — the route across is through the grading table." }, { "question": "What is the difference between single-size and graded aggregate?", "answer": "Whether the material spans a range of particle sizes or is concentrated near one. Graded aggregate contains a spread from fine to coarse, so the smaller particles pack into the spaces between the larger ones — which gives a dense, well-interlocked material that compacts to a stable layer, and is what a sub-base wants. Single-size aggregate is concentrated near one dimension, so it has large voids between its particles and drains freely; that is what a drainage layer, a soakaway or a filter wants, and it is why the same job can call for both. Using one where the other belongs gives either a sub-base that will not compact or a drain that silts up." }, { "question": "Why does maximum aggregate size matter in concrete?", "answer": "Because it has to fit, and because it changes the mix. The stone must pass between the reinforcement and into the corners of the formwork, so the maximum size is limited by the bar spacing, the cover and the section's dimensions — which is why a thin, heavily reinforced element is specified with a smaller aggregate than a mass pour. It also affects the mix economics: larger aggregate reduces the surface area the paste has to coat, so a mix with bigger stone generally needs less cement and less water for the same workability. Reducing the maximum size to get concrete into a congested section is therefore a real change to the mix rather than a substitution." } ], "related": [ "hardcore", "sand" ] }, { "slug": "verge", "concept": "Verge and rake", "family": "envelope", "definition": "The edge of a roof at a gable — where the covering stops at the sloping end of the roof rather than at the eaves. Named differently by market, and the British word has an unrelated highway meaning.", "url": "https://craftquantities.com/glossary/verge/", "names": [ { "market": "UK", "term": "verge", "alsoCalled": [ "gable edge", "barge" ], "exactness": "false-friend", "note": "In highway and landscaping work a verge is the grass strip beside a carriageway — a completely unrelated element that appears on the same site drawings." }, { "market": "AU", "term": "verge", "alsoCalled": [ "gable end", "barge" ], "exactness": "false-friend", "note": "As the UK, and in Australian usage the highway sense is if anything more common — the nature strip beside a road is widely called the verge." }, { "market": "US", "term": "rake", "alsoCalled": [ "rake edge", "gable edge" ], "exactness": "close", "note": "\"Rake\" names the sloping edge itself and the trim along it; American usage has no roofing sense of verge at all." }, { "market": "CA", "term": "rake", "alsoCalled": [ "rake edge", "gable trim" ], "exactness": "close", "note": "As the United States, with the rake board and the drip edge along it named separately from the eaves components." } ], "standards": [ { "market": "UK", "standard": "BS 5534", "covers": "Slating and tiling, including verge detailing and fixing in wind." }, { "market": "US", "standard": "IRC Chapter 9 / ASTM D3161", "covers": "Roof coverings and their wind resistance, including edge details." } ], "calculators": [ { "slug": "roof-squares-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-squares-calculator.json" }, { "slug": "common-rafter-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/common-rafter-length-calculator.json" }, { "slug": "fascia-board-calculator", "json": "https://craftquantities.com/api/v1/calculators/fascia-board-calculator.json" } ], "confusions": [ { "question": "Is the verge the same as the eaves?", "answer": "No — they are the two different edges of a pitched roof and they behave differently. The EAVES is the horizontal lower edge, where water leaves the roof and where the gutter is; the VERGE or rake is the sloping edge at a gable, running from eaves up to ridge, where water is not collected but where wind pressure is highest. That difference in exposure is why verge details are about FIXING and wind rather than about drainage, and why a covering's fixing specification tightens along both the verge and the eaves. A specification that treats the two edges identically has usually not thought about either." }, { "question": "Why does the verge need extra fixing?", "answer": "Because wind uplift is concentrated at edges and corners, and the verge is an edge running the full slope of the roof. Air flowing over a building separates at its edges and generates strong local suction there — considerably higher than over the middle of the roof — so the tiles, slates or sheets along a verge are the ones most likely to be lifted. That is why fixing specifications state a tighter pattern in the perimeter zones than in the field, why dry verge systems and mechanical clips exist, and why a mortar-bedded verge that has begun to crack is a maintenance item rather than a cosmetic one." }, { "question": "What is a bargeboard, and is it part of the verge?", "answer": "It is the board along the verge, and the distinction matters when pricing. The verge is the EDGE — the line where the roof covering stops at the gable. The bargeboard, or rake board in American usage, is the timber or composite board fixed along that edge, closing the ends of the battens or sheathing and finishing the line. So a verge detail might be a dry verge system, a mortar bed, a cloaked tile or an overhanging bargeboard, and each is a different material and a different fixing. Asking for a verge repair without saying which of those is meant leaves the pricing open by a wide margin." } ], "related": [ "soffit", "eaves", "valley" ] }, { "slug": "lintel", "concept": "Lintel and header", "family": "structure", "definition": "The beam over a door, window or other opening that carries the wall above it and delivers that load to the masonry or framing each side. Called a lintel in British and Australian practice and a header in North American framing.", "url": "https://craftquantities.com/glossary/lintel/", "names": [ { "market": "UK", "term": "lintel", "alsoCalled": [ "cavity lintel", "box lintel", "catnic" ], "exactness": "close", "note": "Usually a manufactured steel section or a precast concrete unit rather than timber, and in a cavity wall a single lintel commonly spans both leaves and carries a damp-proof tray." }, { "market": "AU", "term": "lintel", "alsoCalled": [ "head beam", "galvanised lintel" ], "exactness": "close", "note": "As the UK for masonry, but in timber-framed construction the member over an opening is frequently called a head or head trimmer instead." }, { "market": "US", "term": "header", "alsoCalled": [ "door header", "window header", "lintel" ], "exactness": "false-friend", "note": "In British usage a header is a brick laid with its end showing, a header tank is a cold-water cistern, and a header is a pipework manifold. None of them spans an opening." }, { "market": "CA", "term": "header", "alsoCalled": [ "lintel", "built-up header" ], "exactness": "false-friend", "note": "As the United States, with lintel reserved more often for masonry and header used for the timber member in framing." } ], "standards": [ { "market": "UK", "standard": "BS EN 845-2", "covers": "Specification for ancillary components: lintels, including their load classification and testing." }, { "market": "US", "standard": "IRC Table R602.7", "covers": "Prescriptive header spans for wood framing, by species, size and loading condition." } ], "calculators": [ { "slug": "lintel-bearing-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/lintel-bearing-length-calculator.json" }, { "slug": "lintel-load-capacity-calculator", "json": "https://craftquantities.com/api/v1/calculators/lintel-load-capacity-calculator.json" }, { "slug": "steel-i-beam-weight-calculator", "json": "https://craftquantities.com/api/v1/calculators/steel-i-beam-weight-calculator.json" } ], "confusions": [ { "question": "Does a header mean the same thing as a lintel?", "answer": "Structurally yes, materially usually not, and the word itself is a trap in British usage. Both name the member spanning an opening and carrying what sits above it. But an American header is typically built up from dimensional lumber — two or three members nailed together with packing between them, sized from a span table — whereas a British lintel is generally a manufactured steel profile or a precast concrete unit selected from a manufacturer's load tables. So converting a specification is not a matter of swapping the word: a timber header span table has no entry for a cavity-wall steel lintel, and the British lintel additionally carries a damp-proof tray across the cavity that the timber member never had to. And in British usage the word header is already taken three times over, by a brick laid end-on, a cold-water cistern and a pipework manifold." }, { "question": "What is bearing length, and why does it get specified separately?", "answer": "It is how far the lintel sits onto the wall at each end, and it is a separate check because the lintel can be strong enough while the masonry under its ends is not. The load the lintel collects has to pass into the wall through that contact area, so a short bearing concentrates the same force over less masonry and can crush it — which is why manufacturers state a minimum bearing, commonly 100 mm or 150 mm depending on the span and load, and why a padstone appears under a heavily loaded end. It also changes the ORDER LENGTH: the lintel you buy is the clear opening plus two bearings, so a 1,800 mm opening with 150 mm bearings needs a 2,100 mm lintel. Ordering to the opening size is one of the commonest measuring errors on a job." }, { "question": "Why do lintels over cavity walls look so different from solid-wall ones?", "answer": "Because they are doing a second job as well as spanning. A cavity wall has two leaves with a gap between them, and water that crosses the outer leaf has to be caught and sent back out rather than reaching the inner leaf. So a cavity lintel is profiled to support both leaves and to act as a tray, with a rise across the cavity and stop ends, and weep holes are left in the perimeter joint above it so the collected water can escape. A solid-wall lintel only has to span. That is why a cavity lintel is specified by the wall build-up it suits — cavity width, leaf thicknesses, insulation — and not by span and load alone." } ], "related": [ "rsj", "brick-bond" ] }, { "slug": "noggin", "concept": "Noggins and blocking", "family": "structure", "definition": "Short pieces fixed at right angles between studs or between joists, to stiffen them, to stop them twisting, and to give a fixing where a board edge or a heavy fitting lands between members.", "url": "https://craftquantities.com/glossary/noggin/", "names": [ { "market": "UK", "term": "noggin", "alsoCalled": [ "nogging", "dwang", "strutting" ], "exactness": "close", "note": "Dwang is Scottish and northern usage for the same piece; strutting more often names the equivalent between joists rather than between studs." }, { "market": "AU", "term": "nogging", "alsoCalled": [ "noggin", "blocking" ], "exactness": "close", "note": "Both words in use, with nogging the more common in framing documents and blocking increasingly common under American influence." }, { "market": "US", "term": "blocking", "alsoCalled": [ "bridging", "fire blocking", "backing" ], "exactness": "false-friend", "note": "Bridging in North American usage usually means DIAGONAL cross-bracing between joists, not a solid piece — so a British noggin translates to solid blocking, and calling it bridging names a different member." }, { "market": "CA", "term": "blocking", "alsoCalled": [ "strapping", "bridging", "cross-bridging" ], "exactness": "false-friend", "note": "As the United States, and Canadian strapping adds a second trap — it means the light battens run across the underside of joists, not the pieces between them." } ], "standards": [ { "market": "US", "standard": "IRC R502.7 / R602.8", "covers": "Lateral restraint of joists and fireblocking requirements in concealed framing spaces." }, { "market": "UK", "standard": "BS EN 1995-1-1 / Approved Document B", "covers": "Timber structure design, and cavity barriers within concealed spaces in construction." } ], "calculators": [ { "slug": "framing-stud-calculator", "json": "https://craftquantities.com/api/v1/calculators/framing-stud-calculator.json" }, { "slug": "stud-bore-notch-limit-calculator", "json": "https://craftquantities.com/api/v1/calculators/stud-bore-notch-limit-calculator.json" }, { "slug": "linear-feet-to-studs-16-oc-calculator", "json": "https://craftquantities.com/api/v1/calculators/linear-feet-to-studs-16-oc-calculator.json" } ], "confusions": [ { "question": "Are noggins structural, or just somewhere to screw into?", "answer": "Both, and which one governs decides where they go. As structure they stop a slender member buckling sideways or rotating under load, which is why rows appear at intervals along a long stud or across a joist span rather than wherever convenient. As a fixing they carry things a board alone will not hold — a wall-hung basin, a television bracket, a handrail, a heavy cupboard — and those go exactly where the fitting lands, which is a decision made from the layout drawing rather than from a spacing rule. A third role is neither: in some constructions the same piece acts as a cavity barrier or fireblock, and then its material and its fit to the surrounding timber are specified rather than left to the carpenter." }, { "question": "Why does the American word bridging mean something different?", "answer": "Because it names the diagonal version rather than the solid one. Restraint between joists can be provided two ways: a solid piece the full depth of the joist, or a pair of diagonal members crossing between adjacent joists in an X. North American usage calls the solid one blocking and the diagonal one bridging or cross-bridging, and they are ordered, priced and installed differently — diagonal bridging is a much smaller section, cut at an angle, and much faster to fix. British usage tends to call both strutting, distinguishing solid strutting from herringbone strutting. So a drawing that says bridging is not asking for a noggin, and reading it as one changes both the material list and the labour." }, { "question": "Where do noggins go if the drawing does not say?", "answer": "Three places, and only the first is a rule of thumb. First, at the height where board edges meet — plasterboard, sheathing or panelling needs a fixing along every edge, and a horizontal joint between sheets has nothing behind it unless a noggin is put there. Second, wherever a fitting will be hung, taken from the sanitaryware and joinery layouts rather than guessed, because a noggin fixed after the boards are on means cutting the boards. Third, at whatever interval the structural design requires, which for studs is commonly around mid-height on a standard wall and for joists depends on the span. If a drawing shows none at all on a long span, that is worth querying rather than assuming." } ], "related": [ "joist", "stud" ] }, { "slug": "purlin", "concept": "Purlin", "family": "structure", "definition": "A member running horizontally along the length of a roof, at right angles to the slope direction. What it supports depends on the roof system: rafters in traditional carpentry, the roof sheeting itself in portal-frame and metal buildings.", "url": "https://craftquantities.com/glossary/purlin/", "names": [ { "market": "UK", "term": "purlin", "alsoCalled": [ "under-purlin", "side purlin", "Z-purlin" ], "exactness": "false-friend", "note": "In a cut timber roof it supports the rafters at mid-span; in a steel portal frame the same word names the cold-formed Z or C section spanning between frames and carrying the cladding." }, { "market": "AU", "term": "purlin", "alsoCalled": [ "top hat purlin", "C-purlin", "batten" ], "exactness": "false-friend", "note": "As the UK, and in Australian sheet-roofing practice the light top-hat section carrying the sheeting is often called a batten rather than a purlin, with the distinction resting on size rather than on position." }, { "market": "US", "term": "purlin", "alsoCalled": [ "roof purlin", "Z-purlin", "girt" ], "exactness": "false-friend", "note": "Most often the metal-building sense. A girt is the same kind of member on a WALL rather than a roof, and the two are frequently listed together on a schedule." }, { "market": "CA", "term": "purlin", "alsoCalled": [ "purline", "Z-purlin", "girt" ], "exactness": "false-friend", "note": "As the United States, with purline appearing as an older spelling in timber-framing documents." } ], "standards": [ { "market": "US", "standard": "AISI S100 / MBMA Metal Building Systems Manual", "covers": "Design of cold-formed steel members, including purlins and their bracing." }, { "market": "UK", "standard": "BS EN 1993-1-3", "covers": "Design of cold-formed thin-gauge steel members and sheeting, including purlin systems." } ], "calculators": [ { "slug": "purlin-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/purlin-spacing-calculator.json" }, { "slug": "steel-purlin-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/steel-purlin-spacing-calculator.json" }, { "slug": "common-rafter-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/common-rafter-length-calculator.json" } ], "confusions": [ { "question": "Is a purlin the same thing in a timber roof and a steel building?", "answer": "The word is the same and the position in the load path is not, which is why purlin spacing means two different calculations. In a traditional cut roof the rafters run from eaves to ridge and would be too slender to make the trip alone, so a purlin runs along the roof under them and halves the span each rafter has to manage — the purlin supports rafters, and the rafters support the covering. In a portal-frame or metal building there are no rafters: the purlins span between the frames and the sheeting is fixed straight onto them, so purlin spacing is set by what the SHEET can span, not by what the rafter needs. Read a purlin spacing figure out of the wrong system and it is not conservative or generous, it is answering a different question." }, { "question": "What decides purlin spacing?", "answer": "Whichever member is being rescued by the purlin. Where purlins support rafters, the spacing comes from the rafter: its section, species and grade give an allowable span under the roof load, and the purlins are placed to keep every rafter segment inside it — so a heavier rafter can accept purlins further apart. Where the sheeting sits directly on the purlins, the spacing comes from the manufacturer's load-span table for that profile and gauge, checked at the wind uplift for the site, and tightened in the perimeter zones where suction is highest. In both cases the purlin itself then has to span between its own supports, which is a separate check people frequently skip: getting the spacing right does not make the purlin adequate." }, { "question": "What is a girt, and why does it appear next to purlins?", "answer": "It is the same kind of member turned through ninety degrees onto a wall. In a metal building the cladding needs a line of support at intervals in both places: purlins do it on the roof and girts do it on the walls, and both are typically the same family of cold-formed Z or C sections from the same supplier, differing in spacing and in how they are loaded. The practical difference is the direction of the main load — a purlin carries gravity load from snow and the roof build-up, so its strong axis works with it, while a girt mainly resists wind pressure and suction across its face and carries the cladding's self-weight along its length. They appear together on schedules because they are ordered together, and mixing up which line of a schedule is which is an easy way to get the wrong lengths delivered." } ], "related": [ "wall-plate", "roof-truss" ] }, { "slug": "batten", "concept": "Battens, furring and strapping", "family": "envelope", "definition": "A thin strip of timber or metal fixed across a structure to carry a covering, to hold it off the surface behind, or to cover a joint. The word travels across markets; what it is carrying does not.", "url": "https://craftquantities.com/glossary/batten/", "names": [ { "market": "UK", "term": "batten", "alsoCalled": [ "tile batten", "counter-batten", "roofing batten" ], "exactness": "false-friend", "note": "A UK tile batten is a structural component with a graded specification and a gauged spacing set by the covering. A counter-batten runs the other way beneath it to form a drainage and ventilation path." }, { "market": "AU", "term": "batten", "alsoCalled": [ "roof batten", "top hat batten", "ceiling batten" ], "exactness": "close", "note": "Frequently a steel top-hat section rather than timber, and in sheet-roofing practice the batten does the job a purlin does elsewhere." }, { "market": "US", "term": "furring strip", "alsoCalled": [ "furring", "batten", "1x3" ], "exactness": "false-friend", "note": "Furring is usually about levelling a surface or creating an air gap, not about carrying a tile. And board-and-batten names a cladding pattern where the batten is the visible strip over a board joint." }, { "market": "CA", "term": "strapping", "alsoCalled": [ "furring", "batten", "1x3 strapping" ], "exactness": "false-friend", "note": "Canadian strapping is the light battens run across joists or studs before boarding. In UK usage strapping means metal restraint straps tying a wall to a floor, which is a structural component." } ], "standards": [ { "market": "UK", "standard": "BS 5534 / BS EN 15228", "covers": "Batten sizes, grading and fixing for slating and tiling, and preservative treatment." }, { "market": "US", "standard": "ASTM E2925 / IRC Chapter 7", "covers": "Furring and rainscreen assemblies, and requirements for wall covering support." } ], "calculators": [ { "slug": "roof-batten-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-batten-spacing-calculator.json" }, { "slug": "board-and-batten-siding-calculator", "json": "https://craftquantities.com/api/v1/calculators/board-and-batten-siding-calculator.json" }, { "slug": "rain-screen-furring-calculator", "json": "https://craftquantities.com/api/v1/calculators/rain-screen-furring-calculator.json" } ], "confusions": [ { "question": "Is a roofing batten the same as a furring strip?", "answer": "No, and the difference is that one is graded structure and the other is packing. A British roofing batten carries the whole weight of the tiles or slates plus anybody walking on the roof, spans between rafters, and resists the uplift trying to pull the covering off — so it has a specified size, a strength grade, a knot and wane limit, and a preservative treatment, and substituting an ungraded strip of the same dimensions is a real reduction in the roof. A furring strip is normally doing none of that: it levels an uneven surface, holds a covering off the wall to create a drained cavity, or gives a fixing line. Both are thin strips of timber, and only one of them is a structural member." }, { "question": "What does the batten gauge mean, and why is it not simply the tile length?", "answer": "The gauge is the distance from one batten to the next, and it is the tile length MINUS the lap, divided by however many courses cover a given tile. Each course has to overlap the one below by enough to keep water out, so the exposed part of a tile is always shorter than the tile — which is why a 265 mm tile at a 65 mm lap gives a gauge around 100 mm on a double-lap covering rather than anything resembling 265 mm. The lap itself depends on the roof pitch and on the exposure of the site, so the same tile on a shallower roof needs a bigger lap, a tighter gauge, more battens and more tiles. Taking the gauge from a table without checking the pitch it was written for is one of the ways a tile order comes out short." }, { "question": "Why would a roof have battens running in both directions?", "answer": "Because the second set creates a drainage and ventilation path that the first set blocks. Where an underlay is laid over the rafters and the tile battens go straight onto it, each batten sits tight against the underlay and acts as a small dam: water running down the underlay is held at every batten line, and air cannot move up the slope. Counter-battens fixed along the rafters first, with the tile battens across them, lift the whole grid clear so water runs to the eaves and air passes behind the covering. It matters most on low pitches, on long slopes, and wherever the underlay is vapour-permeable and depends on that air movement to work. It also adds a full extra set of timber and a longer fixing to the material list, which is why it should be identified before pricing rather than discovered on site." } ], "related": [ "sarking" ] }, { "slug": "sarking", "concept": "Sarking and roof underlay", "family": "envelope", "definition": "The layer between the rafters and the roof covering. What that layer physically IS varies by market more sharply than almost any other roofing term: boarding in one, a membrane in another, a reflective foil in a third.", "url": "https://craftquantities.com/glossary/sarking/", "names": [ { "market": "UK", "term": "sarking", "alsoCalled": [ "sarking board", "underlay", "roofing felt", "breather membrane" ], "exactness": "false-friend", "note": "In Scottish practice sarking means the timber BOARDING laid over the rafters; in English usage it usually means the membrane laid over them. The same word names a board and a sheet on either side of one border." }, { "market": "AU", "term": "sarking", "alsoCalled": [ "reflective foil laminate", "roof sarking", "anticon" ], "exactness": "false-friend", "note": "Australian sarking is normally a reflective foil laminate, valued for its radiant barrier performance as much as for shedding water — a different material from both the Scottish board and the English membrane." }, { "market": "US", "term": "roofing underlayment", "alsoCalled": [ "felt", "synthetic underlayment", "tar paper" ], "exactness": "absent", "note": "Sarking is not used in American practice at all. The membrane is underlayment, and the boarding beneath it is sheathing or decking — the two jobs the word covers elsewhere have separate names." }, { "market": "CA", "term": "roof underlayment", "alsoCalled": [ "felt", "ice and water shield", "roof deck protection" ], "exactness": "absent", "note": "As the United States, with an additional self-adhering membrane at eaves and valleys named separately because code requires it in most of the country." } ], "standards": [ { "market": "UK", "standard": "BS 5534 / BS EN 13859-1", "covers": "Underlay for discontinuous roofing, its classification, and its role in resisting wind uplift." }, { "market": "US", "standard": "ASTM D226 / ASTM D1970", "covers": "Asphalt-saturated felt underlayment, and self-adhering polymer-modified membranes for ice-dam protection." } ], "calculators": [ { "slug": "roofing-underlayment-calculator", "json": "https://craftquantities.com/api/v1/calculators/roofing-underlayment-calculator.json" }, { "slug": "radiant-barrier-coverage-calculator", "json": "https://craftquantities.com/api/v1/calculators/radiant-barrier-coverage-calculator.json" }, { "slug": "roof-batten-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-batten-spacing-calculator.json" } ], "confusions": [ { "question": "If a specification says sarking, what should be ordered?", "answer": "Ask, because the word alone cannot settle it and the three answers differ by an order of magnitude in cost. A Scottish drawing saying sarking usually means timber boarding fixed over the rafters, which is a structural deck with its own thickness, grade and fixing pattern. An English drawing saying sarking usually means a roll of underlay membrane. An Australian one usually means a reflective foil laminate. Ordering boards against a membrane specification puts several thousand pounds of timber on a job that wanted rolls; ordering rolls against a boarding specification leaves the roof without the deck it was designed around. The tell is normally elsewhere on the drawing — a thickness in millimetres means boards, a roll width and a lap dimension means a membrane, and a reference to emissivity or an R-value means foil." }, { "question": "What is the difference between a breather membrane and a traditional felt?", "answer": "Whether water vapour can pass through it, which decides how the roof space gets rid of moisture. A traditional bitumen felt is effectively closed, so moisture rising from the building has to leave through deliberate ventilation openings at the eaves and ridge, and a roof built with felt and no ventilation path collects condensation on the underside. A vapour-permeable breather membrane lets vapour out through the sheet itself while still shedding liquid water, which is why it can allow a roof to be built with less ventilation — but only when it is installed the way its certification assumes, including the right way up, supported correctly, and usually with an air gap beneath it. Substituting one for the other without revisiting the ventilation is a common cause of a roof that drips in winter." }, { "question": "Does the underlay do anything structural?", "answer": "More than most people expect, which is why it is specified rather than chosen on price. On a tiled or slated roof the underlay is a designed part of the wind resistance: air pressure inside the roof space pushing up against the covering is partly balanced by the underlay, and a sheet that tears, sags too far between rafters or is fixed with too few battens changes the uplift the tiles have to survive. British practice treats it that way explicitly — the underlay's resistance class and its fixing are part of the tiling specification, not an accessory to it. It is also the roof's second line of defence against wind-driven rain and snow, which is why the lap dimensions and the detailing at eaves, valleys and abutments matter as much as the sheet itself." } ], "related": [ "batten" ] }, { "slug": "architrave", "concept": "Architrave and casing", "family": "finishes", "definition": "The moulding fixed around a door or window opening on the face of the wall, covering the joint between the frame or lining and the plaster. Decorative in appearance and a joint cover in function.", "url": "https://craftquantities.com/glossary/architrave/", "names": [ { "market": "UK", "term": "architrave", "alsoCalled": [ "arch", "door architrave", "ogee architrave" ], "exactness": "close", "note": "Names the moulding on the wall face only. The board forming the inside of the opening is the lining, and it is ordered and priced separately." }, { "market": "AU", "term": "architrave", "alsoCalled": [ "door architrave", "arki" ], "exactness": "close", "note": "As the UK, with the reveal board inside the opening called the jamb rather than the lining." }, { "market": "US", "term": "casing", "alsoCalled": [ "door casing", "window casing", "trim" ], "exactness": "false-friend", "note": "In British usage casing means the lining inside the opening, the sheet metal round a boiler, or the tube lining a borehole — never the moulding on the wall face." }, { "market": "CA", "term": "casing", "alsoCalled": [ "door trim", "brickmould", "moulding" ], "exactness": "false-friend", "note": "As the United States, and brickmould is a further trap: it is the exterior casing against the masonry, not an interior moulding at all." } ], "standards": [ { "market": "UK", "standard": "BS 1186-3", "covers": "Timber for joinery: workmanship, including the fit and finish of mouldings and their joints." }, { "market": "US", "standard": "WM series / WDMA I.S.4", "covers": "Standard moulding profile numbers and the specification of wood mouldings." } ], "calculators": [ { "slug": "door-window-casing-calculator", "json": "https://craftquantities.com/api/v1/calculators/door-window-casing-calculator.json" }, { "slug": "baseboard-trim-calculator", "json": "https://craftquantities.com/api/v1/calculators/baseboard-trim-calculator.json" }, { "slug": "crown-molding-calculator", "json": "https://craftquantities.com/api/v1/calculators/crown-molding-calculator.json" } ], "confusions": [ { "question": "How much architrave does one door actually take?", "answer": "Usually more than the obvious sum, and the mitres are why. A single side of a standard doorway takes two vertical legs and one head, and if each leg is cut from the opening height and the head from the opening width you have measured the SHORT edge of a mitred piece — the long edge of each piece is longer by the width of the moulding at each mitred end. Then a door that is trimmed on both faces doubles everything, which people forget on internal doors. Stock lengths make it worse: legs commonly come from a length that leaves an offcut too short for another leg, so the practical order is set by how the stock divides rather than by the total run. Ordering the bare run plus a nominal percentage tends to fall short on a job with many doors." }, { "question": "What is the difference between architrave and the lining?", "answer": "Which surface it covers, and they are two separate orders. The lining — jamb in Australian and American usage — is the board forming the INSIDE of the opening, the surface you see when you stand in the doorway and look at the edge of the wall; it is as wide as the wall is thick, and it is what the door stop and the hinges are fixed to. The architrave is the moulding on the FACE of the wall, covering the joint where the lining meets the plaster. A door set quoted as including casing in North America may include both, whereas a British quote for architrave rarely includes the lining. That is one of the commoner mismatches when a package is priced from a specification written in another market." }, { "question": "Why do some mitres open up and others do not?", "answer": "Because the moulding is still moving after it is fixed, and the mitre is the joint least able to tolerate it. Timber shrinks across its width far more than along its length, so a mitred corner — where the grain of one piece meets the grain of another at forty-five degrees — opens as the two pieces shrink in different directions. That is why a mitre cut in timber delivered wet, or fixed in a building still drying out, is the one that gapes months later, and why MDF mouldings, which move much less across their width, tend to hold a mitre better while being far less tolerant of damp. The other cause is mechanical: a mitre held only by the paint pulls apart, whereas one glued and pinned through the joint stays closed even when the pieces move." } ], "related": [ "skirting" ] }, { "slug": "trap", "concept": "Trap and water seal", "family": "services", "definition": "The bend beneath a sink, basin, bath or toilet that holds a small volume of water permanently, so that the drain beyond it cannot vent sewer gases back into the room. The water is the seal; the fitting only holds it in place.", "url": "https://craftquantities.com/glossary/trap/", "names": [ { "market": "UK", "term": "trap", "alsoCalled": [ "U-bend", "bottle trap", "P-trap", "gully" ], "exactness": "close", "note": "U-bend is used colloquially for any trap regardless of shape, including bottle traps that contain no U at all." }, { "market": "AU", "term": "trap", "alsoCalled": [ "P-trap", "S-trap", "water seal", "gully trap" ], "exactness": "close", "note": "As the UK, with the external gully trap a standard part of the drainage arrangement rather than an occasional fitting." }, { "market": "US", "term": "P-trap", "alsoCalled": [ "trap", "trap seal", "drum trap" ], "exactness": "false-friend", "note": "The shape is named rather than generic: the S-trap is prohibited by plumbing code in most of the country because it siphons dry, so trap and P-trap are used almost interchangeably." }, { "market": "CA", "term": "P-trap", "alsoCalled": [ "trap", "trap arm", "running trap" ], "exactness": "false-friend", "note": "As the United States, and the trap ARM — the pipe between the trap and the vent — is a separately dimensioned component that British documents do not name." } ], "standards": [ { "market": "UK", "standard": "BS EN 12056-2 / Approved Document H", "covers": "Sanitary pipework inside buildings, including trap seal depths and the conditions that break them." }, { "market": "US", "standard": "IPC Chapter 10 / UPC Chapter 10", "covers": "Traps, trap seals, prohibited trap types, and the maximum distance from a trap to its vent." } ], "calculators": [ { "slug": "trap-primer-flow-calculator", "json": "https://craftquantities.com/api/v1/calculators/trap-primer-flow-calculator.json" }, { "slug": "drain-pipe-slope-calculator", "json": "https://craftquantities.com/api/v1/calculators/drain-pipe-slope-calculator.json" }, { "slug": "backflow-preventer-velocity-calculator", "json": "https://craftquantities.com/api/v1/calculators/backflow-preventer-velocity-calculator.json" } ], "confusions": [ { "question": "Why is an S-trap a problem when a P-trap is not?", "answer": "Because of what the outgoing pipe does immediately after the seal. A P-trap turns and runs roughly HORIZONTALLY into the wall, so water leaving the fitting slows and breaks contact with the pipe, and the seal behind it is left full. An S-trap drops VERTICALLY straight down, so a full basin discharging gives the falling column enough momentum to pull the seal out behind it — the trap self-siphons and is left dry, and a dry trap is an open pipe to the drain. That is why American and Canadian codes prohibit the S-trap outright and why British guidance limits the conditions in which a vertical leg is acceptable. The failure is silent: the fitting looks correct and only smells wrong days later, when the remaining water has evaporated as well." }, { "question": "What does trap seal depth mean, and when does it matter?", "answer": "It is the vertical depth of water the trap holds — typically 50 mm or 75 mm — and it is the budget the seal has to survive pressure changes in the drain. Every discharge elsewhere in the system pushes and pulls air past the trap, and each event takes a little water with it. A deeper seal survives more of that, which is why a shallow seal is specified only where the run is short and well vented, and why a shower trap that had to be shallow to fit under the tray is the one most likely to smell. Evaporation spends the same budget: an unused trap loses its seal over weeks, which is why a guest bathroom, a floor gully or a rarely used utility sink smells and a daily-use basin does not." }, { "question": "Is a grease trap the same kind of thing?", "answer": "No, and the shared word causes real specification errors. A sanitary trap exists to hold a water seal against gas, and it is sized in millimetres of seal depth. A grease trap — or grease interceptor — exists to separate fats from wastewater so they cool and solidify before they reach the drain, and it is sized in litres or gallons of retention volume against a flow rate and a retention time. A petrol or silt interceptor does the same job for a different contaminant. They are all called traps, they all sit in a drainage line, and only one of them is about smell. Sizing one with the other's rules produces either a fitting that cannot hold a seal or a chamber far too small for the kitchen it serves." } ], "related": [ "soil-pipe", "gully" ] }, { "slug": "rcd", "concept": "Residual current and ground-fault protection", "family": "services", "definition": "A device that continuously compares the current flowing out along the line with the current returning along the neutral, and disconnects when they differ — because the missing current has found another path to earth, and a person can be that path.", "url": "https://craftquantities.com/glossary/rcd/", "names": [ { "market": "UK", "term": "RCD", "alsoCalled": [ "residual current device", "trip switch", "RCBO", "RCCB" ], "exactness": "close", "note": "An RCD alone does not protect against overload; an RCBO combines residual-current and overcurrent protection in one module, which is what a modern consumer unit mostly contains." }, { "market": "AU", "term": "RCD", "alsoCalled": [ "safety switch", "earth leakage circuit breaker", "RCBO" ], "exactness": "close", "note": "As the UK. Safety switch is the common non-trade term and appears in consumer-facing documents and in tenancy requirements." }, { "market": "US", "term": "GFCI", "alsoCalled": [ "ground fault circuit interrupter", "GFI", "AFCI", "receptacle GFCI" ], "exactness": "close", "note": "Same principle at a lower trip threshold — nominally around 5 mA against the 30 mA typical of a UK RCD — and commonly built into a receptacle rather than into the panel. AFCI is a different device detecting arcing, with no direct UK equivalent." }, { "market": "CA", "term": "GFCI", "alsoCalled": [ "ground fault circuit interrupter", "AFCI", "dual function breaker" ], "exactness": "close", "note": "As the United States under Canadian Electrical Code rules, with dual-function breakers combining ground-fault and arc-fault detection." } ], "standards": [ { "market": "UK", "standard": "BS 7671 (IET Wiring Regulations)", "covers": "Where additional protection by RCD is required, the 30 mA threshold, and disconnection times." }, { "market": "US", "standard": "NFPA 70 (NEC) Article 210.8", "covers": "Locations requiring GFCI protection for personnel, and the class of device required." } ], "calculators": [ { "slug": "breaker-size-calculator", "json": "https://craftquantities.com/api/v1/calculators/breaker-size-calculator.json" }, { "slug": "short-circuit-current-calculator", "json": "https://craftquantities.com/api/v1/calculators/short-circuit-current-calculator.json" }, { "slug": "wire-gauge-voltage-drop-calculator", "json": "https://craftquantities.com/api/v1/calculators/wire-gauge-voltage-drop-calculator.json" } ], "confusions": [ { "question": "Is a GFCI the same as an RCD?", "answer": "The principle is identical and the numbers are not, which matters when reading a specification across markets. Both measure the imbalance between line and neutral current and disconnect when it exceeds a threshold, on the reasoning that the missing current has gone to earth through something — possibly a person. An American GFCI protecting personnel trips at roughly 5 mA; a British RCD providing additional protection trips at 30 mA. The 30 mA figure is not chosen to prevent a shock but to disconnect fast enough that the shock is survivable, which is a different design intent, and it is why British practice pairs the RCD with strict earthing and disconnection-time rules rather than relying on the device alone. Reading one market's threshold into the other's system produces either nuisance tripping or a device that does not do what the code assumed." }, { "question": "What is the difference between an RCD, an RCBO and an MCB?", "answer": "They protect against three different failures, and a board can contain all three. An MCB — miniature circuit breaker — protects the CABLE against too much current, whether from an overload or a short circuit; it does nothing about a current leaking to earth. An RCD protects PEOPLE against that leakage, and does nothing about overload, so an RCD on its own still needs overcurrent protection somewhere upstream. An RCBO is one module doing both jobs for one circuit, which is why a modern consumer unit populated with RCBOs loses only the affected circuit when something trips, where an older board with one RCD covering half the installation loses everything on that side. The American equivalent split is a standard breaker against a GFCI breaker against a dual-function breaker." }, { "question": "Why does an RCD trip when nothing appears to be wrong?", "answer": "Because leakage is normal in small amounts and it accumulates. Every appliance with a filter, a heating element or a long cable run leaks a fraction of a milliamp to earth as a matter of design, and an RCD covering many circuits sums all of it. Add a damp exterior socket, an old immersion element, a freezer and a run of outdoor lighting, and the standing leakage can sit close to the trip threshold — so the device trips on the next small addition rather than on a fault. That is the diagnostic pattern: a trip that follows switching something on has a suspect, while a trip that happens with nothing changing, or only in wet weather, is usually accumulated leakage plus moisture. It is also the practical argument for splitting circuits across separate devices rather than putting one RCD in front of everything." } ], "related": [ "consumer-unit", "earthing" ] }, { "slug": "ring-final-circuit", "concept": "Ring final and branch circuits", "family": "services", "definition": "How the socket outlets in a building are connected back to the board. British practice commonly runs a loop that leaves the board and returns to it; North American practice runs a line that leaves the board and stops. The difference changes the cable size, the protection, and what a plug contains.", "url": "https://craftquantities.com/glossary/ring-final-circuit/", "names": [ { "market": "UK", "term": "ring final circuit", "alsoCalled": [ "ring main", "ring circuit", "radial circuit" ], "exactness": "false-friend", "note": "Ring MAIN is the common trade term and is technically wrong — a main is the supply into the building, not the final circuit off the board. Radial circuits also exist in British practice and are increasingly specified." }, { "market": "AU", "term": "final subcircuit", "alsoCalled": [ "power circuit", "radial circuit" ], "exactness": "close", "note": "Australian practice is radial rather than ring, so the term describes the same position in the system with a different topology behind it." }, { "market": "US", "term": "branch circuit", "alsoCalled": [ "circuit", "small appliance branch circuit", "home run" ], "exactness": "absent", "note": "There is no ring. Each branch circuit leaves the panel and terminates, and loop wiring of socket outlets is not a recognised arrangement." }, { "market": "CA", "term": "branch circuit", "alsoCalled": [ "circuit", "split receptacle circuit" ], "exactness": "absent", "note": "As the United States, with the split-receptacle kitchen arrangement a Canadian particularity that has no British counterpart." } ], "standards": [ { "market": "UK", "standard": "BS 7671 Appendix 15", "covers": "Ring and radial final circuit arrangements, conductor sizes and the conditions for each." }, { "market": "US", "standard": "NFPA 70 (NEC) Article 210", "covers": "Branch circuits: ratings, required outlets, and the circuits a dwelling must have." } ], "calculators": [ { "slug": "outlets-per-circuit-calculator", "json": "https://craftquantities.com/api/v1/calculators/outlets-per-circuit-calculator.json" }, { "slug": "lighting-circuit-load-calculator", "json": "https://craftquantities.com/api/v1/calculators/lighting-circuit-load-calculator.json" }, { "slug": "wire-gauge-voltage-drop-calculator", "json": "https://craftquantities.com/api/v1/calculators/wire-gauge-voltage-drop-calculator.json" }, { "slug": "outlet-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/outlet-spacing-calculator.json" }, { "slug": "ev-charger-circuit-calculator", "json": "https://craftquantities.com/api/v1/calculators/ev-charger-circuit-calculator.json" } ], "confusions": [ { "question": "Why does a British plug have a fuse in it and an American one not?", "answer": "Because the ring circuit protects the cable in the wall, not the flex on the appliance. A ring final circuit is typically protected at 32 A, since current can reach any socket along two paths and the cable is sized on that basis. But the flex on a table lamp is nowhere near able to carry 32 A, so something has to protect it — and that something is the fuse in the plug, sized to the appliance. An American branch circuit is protected at 15 A or 20 A, which the appliance cord can survive, so no fuse in the plug is needed. This is the clearest illustration that the plug is not a national quirk: it is a component of a circuit design, and it exists because the protection upstream is deliberately larger than any one appliance needs." }, { "question": "What actually goes wrong if a ring is broken?", "answer": "It keeps working, which is exactly the danger. Break one leg of a ring — a loose terminal, a screw through a cable, a socket wired through instead of looped — and every outlet still has power, because current simply arrives the long way round. But the circuit is now two radial legs protected by a 32 A device, and a leg carrying its full share of the load on cable sized for a shared ring can overheat without ever tripping anything. Nothing on the surface indicates it. That is why a ring is tested by measuring end-to-end continuity of each conductor and cross-connecting them rather than by checking that the sockets work, and why a break is one of the commonest findings on an inspection of an installation that has been altered by non-electricians." }, { "question": "Is a ring better than a radial?", "answer": "It is a trade, and British practice increasingly chooses radial for new work. A ring uses a smaller conductor for a given load because current shares two paths, which mattered a great deal when copper was scarce after the war and is the reason the arrangement exists at all. It also allows a large floor area on one circuit. Against that: a ring depends on remaining continuous, it is harder to test and far easier to compromise during alterations, and a fault anywhere on it affects a large part of the house. A radial circuit is simpler to verify, simpler to extend, and fails in a more contained way, at the cost of more cable or a larger conductor. Neither is a correction of the other; the ring is a design optimised for a constraint that has largely gone." } ], "related": [ "consumer-unit", "fused-spur", "chase" ] }, { "slug": "tanking", "concept": "Tanking and below-ground waterproofing", "family": "envelope", "definition": "Keeping water out of a structure that sits below the surrounding ground, where water can arrive under pressure rather than merely running down a face. Achieved by a barrier, by the structure itself, or by draining the water away before it reaches the inside.", "url": "https://craftquantities.com/glossary/tanking/", "names": [ { "market": "UK", "term": "tanking", "alsoCalled": [ "structural waterproofing", "Type A barrier", "cavity drain membrane" ], "exactness": "close", "note": "Names the intent rather than the method, and covers three different approaches that BS 8102 separates as Types A, B and C." }, { "market": "AU", "term": "tanking", "alsoCalled": [ "below-ground waterproofing", "basement membrane" ], "exactness": "close", "note": "As the UK, and also used for wet-area waterproofing inside bathrooms, which British usage more often calls a wet-room system." }, { "market": "US", "term": "below-grade waterproofing", "alsoCalled": [ "basement waterproofing", "dampproofing", "foundation waterproofing" ], "exactness": "false-friend", "note": "Waterproofing and DAMPPROOFING are distinct code terms: dampproofing resists moisture only and is not accepted where a hydrostatic head exists. The two are commonly sold as though interchangeable." }, { "market": "CA", "term": "below-grade waterproofing", "alsoCalled": [ "dampproofing", "foundation wrap", "drainage board" ], "exactness": "false-friend", "note": "As the United States, with the drainage layer against the wall treated as a standard component rather than an upgrade." } ], "standards": [ { "market": "UK", "standard": "BS 8102", "covers": "Protection of below-ground structures against water ingress, defining Type A, B and C protection and grades of internal environment." }, { "market": "US", "standard": "IBC 1805 / ASTM D5385", "covers": "When dampproofing suffices and when waterproofing is required, and hydrostatic-pressure testing of membranes." } ], "calculators": [ { "slug": "basement-waterproofing-coating-calculator", "json": "https://craftquantities.com/api/v1/calculators/basement-waterproofing-coating-calculator.json" }, { "slug": "waterproofing-membrane-roll-calculator", "json": "https://craftquantities.com/api/v1/calculators/waterproofing-membrane-roll-calculator.json" }, { "slug": "cavity-drainage-mat-calculator", "json": "https://craftquantities.com/api/v1/calculators/cavity-drainage-mat-calculator.json" } ], "confusions": [ { "question": "What is the difference between Type A, Type B and Type C?", "answer": "Where the water is stopped, and each fails differently. TYPE A is a barrier applied to the structure — a membrane or a coating — so the water is held back at a surface, and the whole system depends on that surface being continuous; a single defect at a service penetration or a construction joint is a leak. TYPE B is the structure itself: concrete designed and detailed to be water-resistant, so there is nothing applied to fail, but the construction joints and the reinforcement cover become the critical items. TYPE C accepts that water will reach the wall and manages it: a cavity drain membrane holds the water off the internal finish and takes it to a drainage channel and a sump, which is maintainable but depends on a pump and its power. British practice frequently combines two, because the combination fails more gracefully than either alone." }, { "question": "Why does tanking so often get applied to the wrong side?", "answer": "Because the accessible side is the inside, and water pressure does not care about access. A barrier on the OUTSIDE of a wall is pushed against the structure by the water, so the pressure helps hold it in place. A barrier on the INSIDE is pushed away from the structure by the same pressure, so it depends entirely on its bond and on the strength of whatever backs it — and a tanking slurry on an internal face of an old wall can be forced off in sheets. That is why external tanking is the preferred arrangement and why internal work is usually specified as a cavity drain system instead, which does not try to resist the pressure at all. The practical consequence for pricing: retrofitting external tanking means excavating, and the excavation is usually the larger number." }, { "question": "Does a damp-proof course do the same job?", "answer": "No — a DPC stops moisture rising through a wall by capillary action, and tanking resists water arriving under pressure. They are different mechanisms with different magnitudes. A DPC is a horizontal barrier a few millimetres thick placed in a bed joint; it deals with water climbing slowly through pore structure, and above ground that is the whole problem. Below ground the water table can stand against the wall with real pressure behind it, and a capillary barrier does nothing about that. This matters when a basement is converted: the walls may well have a functioning DPC at ground level and still be entirely unprotected below it, and a specification that says the walls are damp-proofed has not said they are tanked." } ], "related": [ "dpc", "wet-room" ] }, { "slug": "paving-flag", "concept": "Paving flags, slabs and pavers", "family": "site", "definition": "The individual units laid over a prepared base to form a hard surface. Markets divide them differently: British usage separates large flat flags from small block paviors, while North American usage groups almost all of them as pavers and reserves flagstone for irregular natural stone.", "url": "https://craftquantities.com/glossary/paving-flag/", "names": [ { "market": "UK", "term": "paving flag", "alsoCalled": [ "paving slab", "flag", "patio slab", "block paving" ], "exactness": "false-friend", "note": "A flag is the large flat unit; small rectangular units laid in a pattern are block paving or paviors, and the two are priced, laid and bedded differently." }, { "market": "AU", "term": "paver", "alsoCalled": [ "paving slab", "flag", "brick paver" ], "exactness": "close", "note": "Paver is the general term as in North America, with slab used for the larger units — so Australian usage sits between the two conventions." }, { "market": "US", "term": "paver", "alsoCalled": [ "patio paver", "concrete paver", "flagstone", "hardscape unit" ], "exactness": "false-friend", "note": "Flagstone in American usage means IRREGULAR natural stone, not a regular manufactured slab — close to the opposite of the usual British sense of flag." }, { "market": "CA", "term": "paver", "alsoCalled": [ "patio stone", "paving stone", "slab" ], "exactness": "close", "note": "As the United States, with patio stone common for the larger square units in retail usage." } ], "standards": [ { "market": "UK", "standard": "BS EN 1339 / BS 7533", "covers": "Concrete paving flags, and the structural design and laying of pavements in modular units." }, { "market": "US", "standard": "ASTM C936 / ICPI guidance", "covers": "Solid interlocking concrete paving units and their installation over an aggregate base." } ], "calculators": [ { "slug": "paver-calculator", "json": "https://craftquantities.com/api/v1/calculators/paver-calculator.json" }, { "slug": "paver-base-calculator", "json": "https://craftquantities.com/api/v1/calculators/paver-base-calculator.json" }, { "slug": "paver-polymeric-sand-calculator", "json": "https://craftquantities.com/api/v1/calculators/paver-polymeric-sand-calculator.json" } ], "confusions": [ { "question": "Are flags and block paving interchangeable?", "answer": "They look like alternatives in a catalogue and they behave differently under load, which is why the choice is not only aesthetic. Block paving is many small units, so a wheel load spreads through interlock between them and the pavement flexes without cracking — which is why it is used on driveways and why the edge restraint holding the blocks in is a structural component rather than a trim. A large flag carries the load across its own span and relies on continuous support beneath it; unsupported at a corner, it rocks and eventually cracks, and one cracked flag is a replacement rather than a repair. So a surface that will take vehicles usually wants blocks or a thicker flag on a bound bed, and the laying course, the base depth and the edge detail all change with the choice, not just the unit price." }, { "question": "How much extra should be ordered for cutting?", "answer": "It depends on the pattern and the shape of the area far more than on a flat percentage, and a flat percentage is what usually gets used. A rectangular area laid in a stack or stretcher pattern with units that divide neatly into it can need almost nothing beyond breakages. The same area laid DIAGONALLY generates a cut at every perimeter unit and each cut wastes most of a unit, which is why diagonal and herringbone layouts carry a much larger allowance. Circles, curved edges and a random or mixed-size pattern raise it again, because a cut piece from one position rarely fits another. The other quantity people forget is the laying course and the jointing material, both of which are consumed by the actual depth achieved on site rather than the nominal one." }, { "question": "What does the base under paving actually have to do?", "answer": "Spread the load and stay put, and most failures are a base problem wearing a surface problem's appearance. Paving units transmit load into the layer beneath them, and that layer has to distribute it over ground soft enough that concentrated load would sink — so the sub-base is compacted granular material at a depth set by the traffic and the subgrade, not a token layer to level things up. Above it the laying course is thin and uniform, because its job is to seat the units, not to take out variation in the base. The classic failure is a thick sand bed used to correct an uneven base: it consolidates unevenly under use, and the surface dips exactly where the bed was deepest. The second is an unrestrained edge, which lets the whole field creep outward until the joints open." } ], "related": [ "hardcore" ] }, { "slug": "cill", "concept": "Cill, sill and sill plate", "family": "envelope", "definition": "The horizontal member at the bottom of an opening. Whether that means the weathering piece under a window, the board on the inside, or the timber a wall is framed off depends entirely on the market and on the spelling.", "url": "https://craftquantities.com/glossary/cill/", "names": [ { "market": "UK", "term": "cill", "alsoCalled": [ "window cill", "sill", "window board", "sub-cill" ], "exactness": "false-friend", "note": "Trade usage tends to spell the window component cill and the structural member sill. The internal shelf is a window board, which is a separate item from the external cill." }, { "market": "AU", "term": "sill", "alsoCalled": [ "window sill", "sill trim", "bottom plate" ], "exactness": "close", "note": "One spelling for both, with bottom plate used for the framing member rather than sill plate." }, { "market": "US", "term": "sill", "alsoCalled": [ "sill plate", "mudsill", "stool", "window sill" ], "exactness": "false-friend", "note": "Unqualified, sill usually means the SILL PLATE — the timber bolted to the foundation. The internal shelf under a window is the stool, and the piece beneath it the apron." }, { "market": "CA", "term": "sill", "alsoCalled": [ "sill plate", "sill gasket", "stool" ], "exactness": "false-friend", "note": "As the United States, with the sill gasket between plate and foundation a standard line item." } ], "standards": [ { "market": "UK", "standard": "BS 8000-0 / Approved Document C", "covers": "Workmanship on building sites, and resistance to moisture at openings including cill and DPC detailing." }, { "market": "US", "standard": "IRC R317 / R703", "covers": "Protection against decay for sill plates, and exterior wall covering and flashing at openings." } ], "calculators": [ { "slug": "storefront-sill-flashing-calculator", "json": "https://craftquantities.com/api/v1/calculators/storefront-sill-flashing-calculator.json" }, { "slug": "window-setting-block-calculator", "json": "https://craftquantities.com/api/v1/calculators/window-setting-block-calculator.json" }, { "slug": "opening-flashing-membrane-calculator", "json": "https://craftquantities.com/api/v1/calculators/opening-flashing-membrane-calculator.json" } ], "confusions": [ { "question": "If a drawing says sill, which component is it?", "answer": "In North American practice, unqualified, assume the SILL PLATE — the treated timber bolted to the top of the foundation that the wall framing sits on — because that is the member most drawings are discussing when they say sill without a qualifier. The piece under a window is then usually the window sill on the outside and the STOOL on the inside, with the apron below it. In British practice, unqualified, assume the window component, because the framing equivalent is the sole plate or the wall plate and has its own name. The consequence of getting it wrong is not cosmetic: one is a weathering detail measured in linear metres of stone, cast or uPVC, the other is preservative-treated structural timber with a fixing schedule and a gasket." }, { "question": "What does the drip groove under a cill do, and why does blocking it matter?", "answer": "It stops water tracking back along the underside and reaching the wall. Water running off the face of a window reaches the front of the cill and, left alone, surface tension will carry it around the bottom edge and back inwards along the soffit of the cill until it meets the wall — where it soaks in, exactly where the cill was meant to protect. A groove, or a sharp projecting edge, breaks that path: the water cannot follow the corner and drops clear. It is why the cill projects beyond the face of the wall at all, and why a render or a paint build-up that fills the groove, or a replacement cill fitted flush, reproduces the damp patch the original detail existed to prevent. The same logic governs the stop ends at each side of the cill." }, { "question": "Why does the cill need a DPC or flashing behind it?", "answer": "Because the cill is a joint as well as a surface, and joints leak eventually. Water that gets past the frame, around a failed sealant line or through a porous cill unit arrives on top of the wall beneath the opening, which is a horizontal surface inside the construction — the one place it can sit. A cill DPC or a flashing tray beneath the cill catches that water and returns it outwards, usually with stop ends so it cannot escape sideways into the reveals. This is why the flashing membrane at a window opening is detailed before the window goes in and cannot sensibly be added afterwards, and why replacement windows fitted into an old opening frequently produce damp at the reveals: the new frame is sound and the tray was never there." } ], "related": [ "dpc", "threshold", "double-glazing" ] }, { "slug": "breeze-block", "concept": "Concrete block", "family": "materials", "definition": "The precast unit a masonry wall is built from, larger than a brick and laid in the same bedded courses. Markets divide them by what they are made of, how dense they are, and — in two cases — by a word that no longer describes the material.", "url": "https://craftquantities.com/glossary/breeze-block/", "names": [ { "market": "UK", "term": "concrete block", "alsoCalled": [ "breeze block", "blockwork", "aerated block", "dense block" ], "exactness": "false-friend", "note": "Breeze originally meant coke breeze, the fuel ash the block was made with. Almost no block sold today contains any, and the word now loosely covers lightweight aggregate and aerated blocks that are chemically unrelated." }, { "market": "AU", "term": "concrete block", "alsoCalled": [ "besser block", "blockwork", "masonry block" ], "exactness": "false-friend", "note": "Besser is a manufacturer's name used generically, in the same way Hoover or Biro are — so a specification saying besser block has named a shape and a tradition rather than a product." }, { "market": "US", "term": "CMU", "alsoCalled": [ "concrete masonry unit", "cinder block", "breeze block", "block" ], "exactness": "false-friend", "note": "Cinder block carries the same history as breeze and the same inaccuracy. And in American usage BREEZE BLOCK means the decorative perforated screen block, which is a different product entirely." }, { "market": "CA", "term": "CMU", "alsoCalled": [ "concrete block", "cinder block", "block" ], "exactness": "close", "note": "As the United States under CSA rather than ASTM, with the same cinder-block inaccuracy in everyday speech." } ], "standards": [ { "market": "UK", "standard": "BS EN 771-3 / BS EN 772-1", "covers": "Specification for aggregate concrete masonry units, and the determination of compressive strength." }, { "market": "US", "standard": "ASTM C90 / TMS 402", "covers": "Loadbearing concrete masonry units, and the design of masonry structures." } ], "calculators": [ { "slug": "retaining-wall-block-calculator", "json": "https://craftquantities.com/api/v1/calculators/retaining-wall-block-calculator.json" }, { "slug": "cmu-wall-self-weight-calculator", "json": "https://craftquantities.com/api/v1/calculators/cmu-wall-self-weight-calculator.json" }, { "slug": "cmu-block-grout-calculator", "json": "https://craftquantities.com/api/v1/calculators/cmu-block-grout-calculator.json" } ], "confusions": [ { "question": "Is a breeze block the same as a cinder block?", "answer": "Historically they were close cousins and today neither word describes what is in the bag. Both named a block made with the ash left over from burning fuel — coke breeze in Britain, coal cinders in the United States — which was cheap, plentiful and light. That material is essentially gone from block production, and what a merchant sells under either name today is made with a lightweight aggregate, a dense aggregate, or is an autoclaved aerated block, which is a completely different material made by expanding a cement slurry with aluminium powder. The practical consequence is that the word tells you nothing about the two properties that matter — density and compressive strength — and both are printed on the block or its documentation." }, { "question": "Why does block density matter so much?", "answer": "Because it decides four different things at once and they pull against each other. A DENSE block carries more load, so it goes where the structure needs it; it also conducts heat readily, weighs a great deal to lift, and holds a fixing well. A LIGHTWEIGHT or aerated block insulates far better and can be cut with a hand saw, but carries less, and a heavy fixing into it needs a specific anchor rather than a normal plug — a kitchen cupboard pulling out of an aerated block wall is one of the commonest failures in a converted room. Sound is a fifth axis pulling the other way from insulation: mass blocks sound, so the lightweight block that keeps heat in lets noise through. A specification that names only the size has not specified the block." }, { "question": "What does a breeze block mean in American usage?", "answer": "The decorative screen block, which is not a structural unit at all. Mid-century American and Australian architecture used perforated concrete blocks to build screen walls that admit light and air while giving privacy, and those are what a US supplier means by breeze block — the name comes from the breeze passing through them. They are ornamental, they are laid in a stack bond with reinforcement in the joints, and they are not interchangeable with anything a British specification means by the term. Somebody ordering breeze blocks across markets can quite easily receive a pallet of perforated screen units for a load-bearing inner leaf." } ], "related": [ "cavity-wall" ] }, { "slug": "flashing", "concept": "Flashing at abutments and penetrations", "family": "envelope", "definition": "The sheet material that closes the junction between a roof and something interrupting it — a wall, a chimney, a pipe, a valley — so that water is returned to the surface rather than entering the joint.", "url": "https://craftquantities.com/glossary/flashing/", "names": [ { "market": "UK", "term": "flashing", "alsoCalled": [ "soakers", "cover flashing", "apron", "back gutter", "stepped flashing" ], "exactness": "close", "note": "A slated or plain-tiled abutment uses SOAKERS, one per course under the tiles, with a separate cover flashing over them. The cover flashing alone is not a detail." }, { "market": "AU", "term": "flashing", "alsoCalled": [ "apron flashing", "barge flashing", "storm mould", "over-flashing" ], "exactness": "close", "note": "Sheet-roof dominated, so most flashings are one-piece pressed profiles fixed over the sheeting rather than the interleaved soaker-and-cover pair." }, { "market": "US", "term": "flashing", "alsoCalled": [ "step flashing", "counter flashing", "base flashing", "kickout flashing" ], "exactness": "close", "note": "Step flashing is an L-shaped piece woven into each shingle course — the closest equivalent of a soaker — with counter flashing let into the wall above it. Kickout flashing at the bottom of a run has no standard British name." }, { "market": "CA", "term": "flashing", "alsoCalled": [ "step flashing", "counter flashing", "drip edge" ], "exactness": "close", "note": "As the United States, with drip edge at eaves and rakes a separately specified component that British practice usually details in the tile or the fascia instead." } ], "standards": [ { "market": "UK", "standard": "BS EN 12588 / Lead Sheet Association guidance", "covers": "Rolled lead sheet, its codes and thicknesses, and the maximum piece sizes that limit thermal movement." }, { "market": "US", "standard": "IRC R903.2 / SMACNA Architectural Sheet Metal Manual", "covers": "Where flashing is required at roof and wall intersections, and the detailing of sheet-metal work." } ], "calculators": [ { "slug": "flashing-trim-sheet-calculator", "json": "https://craftquantities.com/api/v1/calculators/flashing-trim-sheet-calculator.json" }, { "slug": "opening-flashing-membrane-calculator", "json": "https://craftquantities.com/api/v1/calculators/opening-flashing-membrane-calculator.json" }, { "slug": "roof-curb-flashing-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-curb-flashing-calculator.json" } ], "confusions": [ { "question": "Is step flashing the same thing as a soaker?", "answer": "They do the same job at the same junction, and the geometry differs enough that one cannot be substituted for the other. A SOAKER is a flat piece folded up the wall and out under one course of slates or plain tiles, invisible once laid, with a separate cover flashing over the top lapping down the wall. STEP FLASHING is an L-shaped piece woven into each shingle course so that its upstand is exposed against the wall in a staircase pattern, with counter flashing let into a chase above it. The systems are two-part in both cases, but the parts sit differently: a British cover flashing steps down over soakers it does not touch, while an American counter flashing overlaps the step flashing directly. Reading one market's detail drawing and ordering the other market's components leaves a junction that looks right and is not." }, { "question": "Why is lead specified in codes rather than thicknesses?", "answer": "Because the code number is the traditional designation and it travels with a colour, which is how it is identified on site. British rolled lead runs from Code 3 to Code 8, each a specific thickness and weight, and each is colour-marked on the roll — so a roofer asks for Code 4 rather than for 1.80 mm. The code is not a free choice: it is selected by application and by the length of the piece, because lead expands and contracts substantially with temperature, and a piece too long for its thickness fatigues and splits at the fixing. That is why a specification gives both a code and a maximum piece length, and why a long abutment is made from several overlapping pieces rather than one continuous run — a detail that looks like extra joints and is actually what stops the lead tearing itself apart." }, { "question": "What is kickout flashing and why does it have no British name?", "answer": "It is the piece at the BOTTOM of a step-flashed run that throws water out into the gutter instead of letting it run down behind the cladding, and its absence is one of the most common and most expensive defects in North American construction — it rots the wall below quietly for years. British practice tends not to name it because the equivalent condition is usually handled differently: the abutment commonly meets a gutter or a lower roof rather than continuing past the eaves line, and where it does continue the cover flashing is dressed to discharge outward as a matter of course. The absence of a word is not the absence of the problem, though. Where a British roof does present that geometry, the same water goes to the same place, and nobody has a standard component to order for it." } ], "related": [ "gutter", "flat-roof-covering" ] }, { "slug": "manhole", "concept": "Drainage access chambers", "family": "services", "definition": "The points at which a buried drain can be reached — to inspect it, to rod it, or to enter it. Markets divide the same range of sizes differently, and the words do not line up at the small end.", "url": "https://craftquantities.com/glossary/manhole/", "names": [ { "market": "UK", "term": "manhole", "alsoCalled": [ "inspection chamber", "access chamber", "rodding eye", "IC" ], "exactness": "false-friend", "note": "Graded by depth and access: a rodding eye takes a rod only, an inspection chamber takes an arm, and a manhole is deep enough that a person enters — which makes it a confined space with all that follows." }, { "market": "AU", "term": "inspection opening", "alsoCalled": [ "IO", "inspection shaft", "maintenance hole", "manhole" ], "exactness": "close", "note": "Maintenance hole is increasingly the official term in Australian and New Zealand documents, with manhole surviving in speech." }, { "market": "US", "term": "manhole", "alsoCalled": [ "maintenance hole", "cleanout", "access structure" ], "exactness": "false-friend", "note": "A CLEANOUT is a capped opening in the pipe itself, not a chamber. It is the nearest thing to a rodding eye and is NOT the equivalent of a British inspection chamber, which is a boxed structure with a benched invert." }, { "market": "CA", "term": "maintenance hole", "alsoCalled": [ "manhole", "cleanout", "catch basin" ], "exactness": "false-friend", "note": "As the United States, and a catch basin is a further trap — it is a surface water inlet with a sump, not an access chamber on a foul drain." } ], "standards": [ { "market": "UK", "standard": "Approved Document H / BS EN 476", "covers": "Drainage and waste disposal, including where access must be provided and the sizes of chamber for each depth." }, { "market": "US", "standard": "IPC Chapter 7 / ASTM C478", "covers": "Sanitary drainage cleanout requirements and spacing, and precast reinforced concrete manhole sections." } ], "calculators": [ { "slug": "manhole-ring-segment-calculator", "json": "https://craftquantities.com/api/v1/calculators/manhole-ring-segment-calculator.json" }, { "slug": "drain-pipe-slope-calculator", "json": "https://craftquantities.com/api/v1/calculators/drain-pipe-slope-calculator.json" }, { "slug": "storm-drain-slope-calculator", "json": "https://craftquantities.com/api/v1/calculators/storm-drain-slope-calculator.json" } ], "confusions": [ { "question": "Is a cleanout the same as an inspection chamber?", "answer": "No, and pricing one against the other is a substantial error in both directions. A CLEANOUT is a fitting in the pipe run with a removable cap, brought to the surface in a small box or a cover — it lets a rod or a jetting hose into the pipe and nothing else. A British INSPECTION CHAMBER is a structure: a chamber of a specified internal size, with the drain running through it in an open channel, benching sloped up each side so that flow is guided and solids are not left standing, and a cover rated for the traffic above it. One is a fitting costing tens of pounds, the other is an excavation with a base, a chamber, benching and a cover. An American drawing that calls for cleanouts translated as inspection chambers multiplies the drainage cost several times over." }, { "question": "When does a chamber become a manhole, and why does it matter?", "answer": "When it is deep enough that a person has to go in, and it matters because that changes it from a builder's item into a confined space. British guidance grades access by depth: shallow chambers are worked from the surface with an arm and a rod, and at greater depth the chamber has to be large enough to enter, with step irons or a ladder, and with the cover size to admit somebody wearing equipment. Entering it is then a controlled operation with gas testing, ventilation, a rescue plan and a permit — because a foul drainage chamber can hold hydrogen sulphide and can be oxygen-deficient, and both have killed people who went in to clear a blockage. That is the practical reason to design a system with as few deep chambers as the falls allow." }, { "question": "What is benching, and what happens without it?", "answer": "Benching is the sloped concrete either side of the open channel in the base of a chamber, rising from the channel to the chamber walls. Its job is to keep the flow moving and to shed anything that surcharges back into the channel rather than leaving it stranded on a flat shelf. A chamber built with a flat base instead is a settling tank: solids drop out where the velocity falls, build up, and eventually block the outgoing pipe — so the access provided to clear blockages becomes the place that causes them. The same logic explains the channel itself being a half pipe rather than a box: the flow keeps its depth and its speed through the chamber instead of spreading out and slowing down." } ], "related": [ "soil-pipe" ] }, { "slug": "dado-rail", "concept": "Dado rail and chair rail", "family": "finishes", "definition": "A moulding running horizontally around a room partway up the wall, dividing the wall into a lower and an upper zone that are usually decorated differently.", "url": "https://craftquantities.com/glossary/dado-rail/", "names": [ { "market": "UK", "term": "dado rail", "alsoCalled": [ "chair rail", "dado", "waist moulding" ], "exactness": "close", "note": "Named from the dado — in classical architecture the lower part of a wall treated as the pedestal of a column — so the rail marks the TOP of that zone rather than the back of a chair." }, { "market": "AU", "term": "dado rail", "alsoCalled": [ "chair rail", "picture rail" ], "exactness": "false-friend", "note": "Picture rail is a different moulding entirely, set much higher near the cornice and designed to hang pictures from. The two get conflated in conversation and never in a specification." }, { "market": "US", "term": "chair rail", "alsoCalled": [ "dado cap", "chair molding" ], "exactness": "close", "note": "Named for the furniture it protects the wall from, which implies a height set by a chair back — typically lower than the classical dado line, and the reason the same room reads differently under the two conventions." }, { "market": "CA", "term": "chair rail", "alsoCalled": [ "dado rail", "chair molding" ], "exactness": "close", "note": "As the United States, with dado rail understood and used more often than south of the border." } ], "standards": [ { "market": "UK", "standard": "BS 1186-3", "covers": "Timber for joinery: workmanship, including the fit of mouldings and the tolerance on their joints." }, { "market": "US", "standard": "WM series / WDMA I.S.4", "covers": "Standard moulding profile numbers and the specification of wood mouldings." } ], "calculators": [ { "slug": "baseboard-trim-calculator", "json": "https://craftquantities.com/api/v1/calculators/baseboard-trim-calculator.json" }, { "slug": "crown-molding-calculator", "json": "https://craftquantities.com/api/v1/calculators/crown-molding-calculator.json" }, { "slug": "door-window-casing-calculator", "json": "https://craftquantities.com/api/v1/calculators/door-window-casing-calculator.json" } ], "confusions": [ { "question": "How high should it go, and why do the two names disagree?", "answer": "Because they descend from two different ideas of the thing. The classical DADO is the pedestal zone of a wall, and its proportions come from the order the room is imitating — which puts the rail somewhere around a fifth to a quarter of the wall height, so it rises in a tall room and drops in a low one. The American CHAIR RAIL is named for what it protects the plaster from, which fixes it at the height of a chair back regardless of the ceiling. In a standard modern room the two land close enough that nobody notices; in a tall Victorian room they are far apart, and a chair-rail height in a four-metre room reads as a mistake because the proportion is wrong even though the function is served. The practical rule is that the rail should relate to the openings in the room — ideally aligning with a window cill or a door rail — rather than to a number." }, { "question": "Is a picture rail the same thing higher up?", "answer": "No, it is a different component with a working job. A picture rail is a moulding set near the top of the wall, usually just below the cornice, with a lipped profile shaped to take a hook — so pictures hang from cords rather than from nails driven into the plaster. That was the point of it: in a lath-and-plaster room, hanging from the rail avoids making holes in a surface that does not take them well, and it lets a picture be moved without repair. A dado rail has no such profile and will not hold a hook. Both are horizontal mouldings on a wall, and confusing them on an order produces a length of the wrong section that cannot do either job." }, { "question": "How much does a room actually take, and why is it more than the perimeter?", "answer": "The run is the perimeter of the room minus the door openings, plus the length lost to mitres and plus what is spoiled in cutting. Two things push it past the obvious figure. Every external corner is mitred, and the long edge of a mitred piece is longer than the wall it covers by the depth of the moulding at each end — so a bay window with five short returns loses noticeably more than a plain wall of the same length. And the stock length is what actually governs: mouldings come in fixed lengths, and a wall a little longer than one stock length needs two, leaving an offcut usually too short to be the next wall. Ordering the bare perimeter plus a flat percentage tends to come up short in rooms with many corners and over-order in plain ones." } ], "related": [ "skirting" ] }, { "slug": "scaffold", "concept": "Scaffold members", "family": "site", "definition": "The tubes making up a tube-and-fitting or system scaffold: the verticals carrying load to the ground, the horizontals running along the face, and the horizontals running into the building.", "url": "https://craftquantities.com/glossary/scaffold/", "names": [ { "market": "UK", "term": "standard, ledger, transom", "alsoCalled": [ "upright", "putlog", "brace", "sole plate" ], "exactness": "false-friend", "note": "STANDARD is the vertical, LEDGER the horizontal along the face, TRANSOM the horizontal across it. A putlog scaffold has one row of standards and rests its transoms in the wall, which is a different structure from an independent scaffold." }, { "market": "AU", "term": "standard, ledger, transom", "alsoCalled": [ "upright", "bearer", "putlog" ], "exactness": "close", "note": "British terms under Australian standards, with bearer used where British usage says transom in some system-scaffold documentation." }, { "market": "US", "term": "post, runner, bearer", "alsoCalled": [ "upright", "ledger", "leg", "putlog" ], "exactness": "false-friend", "note": "POST is the vertical, RUNNER the horizontal along the face, BEARER the one across it carrying the platform. Ledger is used loosely for a runner — and in American CARPENTRY a ledger is the board bolted to a wall carrying a deck, which is not a scaffold member at all." }, { "market": "CA", "term": "post, ledger, bearer", "alsoCalled": [ "runner", "upright", "stringer" ], "exactness": "false-friend", "note": "As the United States, with the same carpentry collision on ledger." } ], "standards": [ { "market": "UK", "standard": "TG20 / BS EN 12811-1", "covers": "Good practice guidance for tube-and-fitting scaffolds, and the performance requirements for temporary works equipment." }, { "market": "US", "standard": "OSHA 29 CFR 1926 Subpart L", "covers": "Scaffolds: capacity, platform construction, access, fall protection and competent-person duties." } ], "calculators": [ { "slug": "scaffold-face-area-calculator", "json": "https://craftquantities.com/api/v1/calculators/scaffold-face-area-calculator.json" }, { "slug": "scaffold-baseplate-bearing-calculator", "json": "https://craftquantities.com/api/v1/calculators/scaffold-baseplate-bearing-calculator.json" }, { "slug": "temp-fence-panel-count-calculator", "json": "https://craftquantities.com/api/v1/calculators/temp-fence-panel-count-calculator.json" }, { "slug": "toe-board-compliance-calculator", "json": "https://craftquantities.com/api/v1/calculators/toe-board-compliance-calculator.json" }, { "slug": "ladder-setup-angle-calculator", "json": "https://craftquantities.com/api/v1/calculators/ladder-setup-angle-calculator.json" }, { "slug": "extension-ladder-height-calculator", "json": "https://craftquantities.com/api/v1/calculators/extension-ladder-height-calculator.json" } ], "confusions": [ { "question": "Which tube is which, across the markets?", "answer": "Take them by direction and the translation is mechanical. The VERTICAL that carries load down to the ground is a standard in British and Australian usage and a post or leg in American. The HORIZONTAL running along the face of the building, tying the standards together lengthways, is a ledger in British usage and a runner in American. The horizontal running ACROSS, from the outer standards towards the wall, carrying the boards, is a transom in British usage and a bearer in American. The trap is ledger, which American practice also uses loosely for a runner, so a mixed-vocabulary drawing can have ledger meaning either the along-the-face member or the across member depending on which page you are reading. Direction is unambiguous and the words are not: describe the member by where it runs before ordering anything." }, { "question": "What is the difference between a putlog and an independent scaffold?", "answer": "Whether the building is carrying part of the scaffold. A PUTLOG scaffold has a single row of standards away from the wall, and the inner end of each transom — the putlog — is flattened and rests in a hole left in the masonry, so the wall takes that load. It is cheap, it uses far less tube, and it only works on a building with masonry able to take it, which in practice means new brickwork being built up behind it. An INDEPENDENT scaffold has two rows of standards and stands on its own, tied to the building for stability but not supported by it, which is why it is the normal choice for refurbishment, for cladding, and for anything where the wall's condition is not known. The difference is not a preference: putting a putlog scaffold against a wall that cannot take it is how a scaffold comes down." }, { "question": "Why does a scaffold have a sole plate, and what happens without one?", "answer": "Because the base plate at the foot of each standard concentrates the whole leg load onto a small area, and most ground cannot take it. The sole plate — a timber or a proprietary spreader under the base plate — spreads that load over enough ground to keep the bearing pressure within what the soil can carry. Without one, or with one on soft or recently disturbed ground, the standard settles: not dramatically, just enough to take the scaffold out of level, which throws load onto the ties and the braces that were never designed to carry it. It is why the ground beneath a scaffold is a design input rather than a detail, why scaffolds on pavements sit on plates rather than on the slabs, and why a scaffold erected over a newly backfilled trench is a specific and well-known hazard." } ], "related": [ "skip", "acrow-prop" ] }, { "slug": "immersion-heater", "concept": "Immersion heater", "family": "services", "definition": "An electric resistance element inserted into a hot water cylinder to heat the water directly. What varies is whether it is the primary heat source or a backup to something else — and that difference reshapes the whole system around it.", "url": "https://craftquantities.com/glossary/immersion-heater/", "names": [ { "market": "UK", "term": "immersion heater", "alsoCalled": [ "immersion", "immersion element", "backup immersion" ], "exactness": "absent", "note": "Normally a BACKUP in a cylinder heated by a boiler or a heat pump, on its own circuit with its own switch, used when the primary source is off or has failed." }, { "market": "AU", "term": "element", "alsoCalled": [ "heating element", "booster element", "immersion heater" ], "exactness": "close", "note": "Electric storage water heating is common, so the element is frequently the primary source rather than the backup — and a solar hot water system's element is called the booster." }, { "market": "US", "term": "heating element", "alsoCalled": [ "upper element", "lower element", "water heater element" ], "exactness": "absent", "note": "There is no separate word, because an electric water heater IS a tank with elements: typically two, upper and lower, staged so the top of the tank recovers first. Nothing is being backed up." }, { "market": "CA", "term": "heating element", "alsoCalled": [ "upper element", "lower element" ], "exactness": "absent", "note": "As the United States, with the same two-element staged arrangement standard." } ], "standards": [ { "market": "UK", "standard": "BS EN 60335-2-73 / BS 7671", "covers": "Safety of fixed immersion heaters, and the electrical installation requirements for the circuit serving one." }, { "market": "US", "standard": "UL 174 / NFPA 70 Article 422", "covers": "Household electric storage tank water heaters, and the branch circuit and disconnect requirements for appliances." } ], "calculators": [ { "slug": "water-heater-recovery-time-calculator", "json": "https://craftquantities.com/api/v1/calculators/water-heater-recovery-time-calculator.json" }, { "slug": "water-heater-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/water-heater-sizing-calculator.json" }, { "slug": "tankless-water-heater-calculator", "json": "https://craftquantities.com/api/v1/calculators/tankless-water-heater-calculator.json" } ], "confusions": [ { "question": "Why is an immersion heater a backup in Britain and the main thing in America?", "answer": "Because the systems grew from different starting points. British houses are overwhelmingly heated by a gas boiler, and once a boiler is present it is by far the cheapest way to heat water too — so the cylinder takes a coil from the boiler and the electric element is there for summer, for a boiler breakdown, or for a cheap overnight tariff. American electric water heating grew up without that boiler in the picture, so the tank and its elements are the whole appliance. The consequence when reading across markets is that a specification saying 'water heater' in American usage names a complete appliance, while a British cylinder specification names a vessel and says separately what heats it. Ordering one against the other leaves either a tank with no heat source or a duplicate." }, { "question": "Why does an immersion heater take so long, and why does the top get hot first?", "answer": "Because the power is modest and the water stratifies. A typical domestic element is around three kilowatts, and raising a 150 litre cylinder through 45 degrees takes roughly nine kilowatt hours of energy — so about three hours at full power even before losses, against a boiler putting in five or six times that rate. The stratification is the useful part: hot water is less dense, so it sits at the top and does not mix downward, which means the top of the cylinder reaches temperature long before the bottom. That is why an element near the top gives a usable amount of hot water quickly while a full reheat takes hours, why American tanks stage an upper and a lower element deliberately, and why a British cylinder often has two immersion positions for exactly the same reason." }, { "question": "What actually fails, and what does that say about the water?", "answer": "Three things, and each points somewhere different. The ELEMENT itself burns out, usually after scaling up in a hard-water area — scale insulates the element from the water, so it runs hotter than it was designed to and fails, which makes a short element life a statement about the water rather than about the part. The THERMOSTAT fails, and the symptom is either no heat at all or water far too hot, which is the dangerous one and is the reason a system has a separate non-resettable thermal cut-out behind the thermostat. And the SACRIFICIAL ANODE in the cylinder is consumed — it is there to corrode instead of the tank, and once it is gone the tank starts. An element replaced repeatedly in the same cylinder is usually a water-treatment question." } ], "related": [ "hot-water-cylinder" ] }, { "slug": "wall-tie", "concept": "Wall ties and veneer anchors", "family": "structure", "definition": "The metal components crossing the cavity between an outer and an inner leaf, transferring lateral load between them while carrying no vertical load and returning no water across the gap.", "url": "https://craftquantities.com/glossary/wall-tie/", "names": [ { "market": "UK", "term": "wall tie", "alsoCalled": [ "cavity tie", "butterfly tie", "double-triangle tie", "housing tie" ], "exactness": "close", "note": "Both leaves are usually structural, so the tie makes them act together against wind. Type and spacing come from a schedule set by cavity width, wall height and exposure." }, { "market": "AU", "term": "wall tie", "alsoCalled": [ "cavity tie", "brick tie", "veneer tie" ], "exactness": "close", "note": "Both patterns in use — a true cavity wall and a brick veneer over a timber or steel frame — so the term covers the British and the American case and the drawing has to say which." }, { "market": "US", "term": "veneer anchor", "alsoCalled": [ "brick tie", "wall tie", "corrugated tie", "adjustable anchor" ], "exactness": "false-friend", "note": "A brick veneer is NOT structural: it hangs off the frame or the backup wall and carries only itself. The anchor restrains it laterally, and the corrugated strip commonly used has nothing like the stiffness of a cavity-wall tie." }, { "market": "CA", "term": "veneer tie", "alsoCalled": [ "brick tie", "masonry anchor", "wall tie" ], "exactness": "false-friend", "note": "As the United States under CSA, with corrosion-resistance requirements driven by a harsher freeze-thaw exposure." } ], "standards": [ { "market": "UK", "standard": "BS EN 845-1 / PD 6697", "covers": "Specification for wall ties, and recommendations for their type, spacing and embedment by cavity width and exposure." }, { "market": "US", "standard": "TMS 402 Chapter 12 / ASTM A951", "covers": "Anchored veneer requirements, anchor spacing and area limits, and steel wire for masonry joint reinforcement." } ], "calculators": [ { "slug": "wall-tie-density-calculator", "json": "https://craftquantities.com/api/v1/calculators/wall-tie-density-calculator.json" }, { "slug": "cavity-wall-weep-hole-calculator", "json": "https://craftquantities.com/api/v1/calculators/cavity-wall-weep-hole-calculator.json" }, { "slug": "brick-calculator", "json": "https://craftquantities.com/api/v1/calculators/brick-calculator.json" } ], "confusions": [ { "question": "Is a brick tie the same as a wall tie?", "answer": "The words are used interchangeably and the walls they belong to are not. A British cavity wall has TWO structural leaves, and the ties make them act as one against wind pressure — so the tie is a stiffness component, its type is selected against the cavity width and the exposure, and its spacing comes from a schedule. An American brick veneer is a single skin hung in front of a frame or a backup wall; it carries nothing but its own weight, and the anchor exists only to stop it falling away or being pushed in. That is why a corrugated strip is acceptable there and would be nowhere near adequate as a cavity-wall tie. Reading one market's spacing table into the other's wall is not conservative in either direction: it is answering a different structural question." }, { "question": "Why do wall ties fail, and what does it look like?", "answer": "Corrosion, and it announces itself in a very specific way. A mild steel tie embedded in mortar rusts, and rust occupies several times the volume of the steel it came from — so the tie expands inside the bed joint and lifts the brickwork above it. Because ties sit at a regular vertical spacing, the result is HORIZONTAL cracking at regular intervals up the wall, commonly every few courses, sometimes with the outer leaf bulging outward as the cumulative lift adds up. That pattern is close to diagnostic: very little else produces regularly spaced horizontal cracks. It is a particular concern in walls of the era when ties were mild steel with a thin coating, and it is why modern ties are stainless." }, { "question": "Why does the tie have a drip or a twist in the middle?", "answer": "To stop it carrying water across the cavity, which is the whole point of having a cavity. Water crossing the outer leaf runs down the inside face of it, and anything bridging the gap gives that water a path to the inner leaf — so the tie is shaped to break the path: a twist, a kink, or a formed drip at the centre makes the water gather and fall rather than track along. It also has to be installed the right way up and sloping very slightly toward the OUTER leaf, and it must be kept clear of mortar droppings, because a tie buried in a lump of mortar that spans the cavity is a bridge whatever shape it is. Cavity-wall damp that appears in a regular pattern up a wall is very often mortar on the ties rather than the ties themselves." } ], "related": [ "cavity-wall", "anchor" ] }, { "slug": "soakaway", "concept": "Soakaway and infiltration structures", "family": "site", "definition": "A void in the ground that receives surface water and lets it disperse into the surrounding soil, rather than discharging it to a sewer or a watercourse. Sized by how fast that soil accepts water and by how much water arrives.", "url": "https://craftquantities.com/glossary/soakaway/", "names": [ { "market": "UK", "term": "soakaway", "alsoCalled": [ "soakage pit", "infiltration crate", "rubble soakaway" ], "exactness": "close", "note": "Covers both the traditional stone-filled pit and the modern modular crate system, which hold very different volumes of water per volume of excavation." }, { "market": "AU", "term": "soakwell", "alsoCalled": [ "soak well", "absorption trench", "leach drain" ], "exactness": "close", "note": "Soakwell normally means a precast concrete or polymer chamber rather than a filled pit, and is a standard stocked product in a way the British equivalent is not." }, { "market": "US", "term": "drywell", "alsoCalled": [ "dry well", "seepage pit", "infiltration trench", "French drain" ], "exactness": "false-friend", "note": "French drain is the trap: in American usage it frequently means a perforated pipe in gravel that CONVEYS water elsewhere, which is a different job from dispersing it into the ground." }, { "market": "CA", "term": "drywell", "alsoCalled": [ "soakaway pit", "infiltration gallery", "sump" ], "exactness": "close", "note": "As the United States, with frost depth a governing constraint that milder markets do not have to design around." } ], "standards": [ { "market": "UK", "standard": "BRE Digest 365 / Approved Document H3", "covers": "Soakaway design, including the percolation test method and the storage volume calculation." }, { "market": "US", "standard": "ASTM D3385 / local stormwater manuals", "covers": "Infiltration rate of soils using a double-ring infiltrometer, and jurisdiction-specific sizing rules." } ], "calculators": [ { "slug": "french-drain-calculator", "json": "https://craftquantities.com/api/v1/calculators/french-drain-calculator.json" }, { "slug": "picp-infiltration-storage-calculator", "json": "https://craftquantities.com/api/v1/calculators/picp-infiltration-storage-calculator.json" }, { "slug": "sheet-drain-rate-calculator", "json": "https://craftquantities.com/api/v1/calculators/sheet-drain-rate-calculator.json" } ], "confusions": [ { "question": "Why does a soakaway need a percolation test rather than a rule of thumb?", "answer": "Because the soil is the whole design and it varies enormously over short distances. A soakaway has to store the water that arrives during a storm and release it into the ground before the next one, so its size is set by two numbers: the volume arriving, which comes from the roof or paved area and the design rainfall, and the rate the ground accepts it, which comes from a test. That rate can differ by a factor of a hundred between a sandy gravel and a clay, and it can differ substantially between two corners of the same garden. The test — BRE Digest 365's method fills a pit three times and times the fall from 75% to 25% full — exists because that number cannot be guessed. A soakaway sized without it is either several times bigger than needed or useless, and the useless case is the one that shows up as a flooded lawn." }, { "question": "How much water does a rubble-filled pit actually hold?", "answer": "Around a quarter to a third of its own volume, which is the fact that surprises people pricing one. Water is stored in the VOIDS between the stones, not in the stones, so a pit filled with clean single-size aggregate stores roughly 30% of the excavation — meaning a soakaway needing three cubic metres of storage needs about ten cubic metres of hole. Modern modular crates exist precisely because of that arithmetic: they are around 95% void, so the same storage fits in a little over three cubic metres of excavation, and on a constrained site that difference decides whether a soakaway is possible at all. The trade is cost per unit and the need for a silt trap upstream, because a crate cannot be dug out and washed the way a stone pit theoretically can." }, { "question": "Where can a soakaway NOT go?", "answer": "Close to a building, close to a boundary, in ground that is already wet, and above certain things. British guidance keeps them a minimum distance from any structure — commonly five metres — because the whole purpose of the thing is to put water into the ground, and putting it next to a foundation is putting it under the foundation. They cannot work where the water table rises into them seasonally, which is why a test done in August and a soakaway used in February can disagree completely. They are restricted over contaminated ground, in groundwater protection zones, and where infiltration could destabilise a slope. The commonest real-world failure is none of these: it is a soakaway discharging into ground that was disturbed and backfilled during the build, which behaves nothing like the ground that was tested." } ], "related": [ "hardcore", "sustainable-drainage" ] }, { "slug": "combi-boiler", "concept": "Combination boiler", "family": "services", "definition": "A single wall-mounted appliance that heats a wet central heating circuit AND produces domestic hot water on demand, with no stored hot water and no cold water tank.", "url": "https://craftquantities.com/glossary/combi-boiler/", "names": [ { "market": "UK", "term": "combi boiler", "alsoCalled": [ "combination boiler", "combi", "instantaneous boiler" ], "exactness": "absent", "note": "The dominant arrangement in British housing. The alternatives are named against it — a system boiler and a heat-only boiler both keep a cylinder, and a combi is defined by not having one." }, { "market": "AU", "term": "combi boiler", "alsoCalled": [ "continuous flow hot water", "instantaneous gas" ], "exactness": "absent", "note": "Hydronic heating is uncommon, so the hot-water half of the idea exists widely as continuous-flow gas and the heating half rarely does." }, { "market": "US", "term": "combi boiler", "alsoCalled": [ "combination boiler", "tankless water heater", "boiler" ], "exactness": "false-friend", "note": "A TANKLESS WATER HEATER does the hot water only and does not heat the house. American combi boilers exist and are a specialist product; the default is a furnace or heat pump for heating plus a separate water heater." }, { "market": "CA", "term": "combi boiler", "alsoCalled": [ "combination boiler", "tankless coil", "on-demand" ], "exactness": "false-friend", "note": "As the United States, with hydronic heating more common, so a true combi is less unusual than south of the border." } ], "standards": [ { "market": "UK", "standard": "BS EN 15502 / Gas Safe requirements", "covers": "Gas-fired central heating boilers, and who may lawfully install or work on one." }, { "market": "US", "standard": "ASME CSD-1 / NFPA 54", "covers": "Controls and safety devices for automatically fired boilers, and the national fuel gas code." } ], "calculators": [ { "slug": "tankless-water-heater-calculator", "json": "https://craftquantities.com/api/v1/calculators/tankless-water-heater-calculator.json" }, { "slug": "water-heater-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/water-heater-sizing-calculator.json" }, { "slug": "boiler-makeup-water-calculator", "json": "https://craftquantities.com/api/v1/calculators/boiler-makeup-water-calculator.json" } ], "confusions": [ { "question": "Is a combi boiler the same as a tankless water heater?", "answer": "It contains one and is not one. A tankless water heater heats domestic hot water on demand and does nothing else; a combi does that AND runs the radiators, switching between the two with a diverter valve that gives hot water priority — which is why the heating drops out briefly while somebody runs a bath and then comes back. Specifying one against the other across markets leaves either a house with hot taps and no heating, or a duplicated appliance. The second difference matters for sizing: a tankless unit is sized on hot water flow alone, while a combi is sized on the LARGER of its two duties, and for most British houses that is the hot water rather than the heat loss — which is why combis are routinely far more powerful than the house needs for heating." }, { "question": "Why does a combi struggle with two showers at once?", "answer": "Because it heats water as it flows, so its output is a flow RATE at a temperature rise, not a quantity. A combi rated at 30 kW can lift roughly twelve litres a minute by about 35 degrees — enough for one good shower. Open a second outlet and the same energy is spread across twice the flow, so both run cooler, or the flow regulator holds the temperature and halves the flow instead. A stored-cylinder system behaves completely differently: it has a reservoir, so it will serve several outlets at full flow until the reservoir runs out and then serve none. That is the real trade between the two, and it is why a house with two bathrooms in simultaneous use is frequently the wrong house for a combi regardless of the boiler's rating." }, { "question": "Why does the incoming water temperature change what a combi can do?", "answer": "Because the boiler's job is the temperature RISE, and the rise it has to deliver changes with the season. Mains water arrives at perhaps 20 degrees in late summer and perhaps 5 in February, and a shower wants around 40 — so the same appliance is being asked for a 20-degree lift in one season and a 35-degree lift in the other, which is three quarters more energy for the identical shower. That is why a combi that was adequate in September feels weak in January, why manufacturers quote flow rate at a stated rise and the quoted figure is usually the generous one, and why a specification should state the rise it assumes. A flow rate quoted without a temperature rise is not a specification." } ], "related": [ "hot-water-cylinder" ] }, { "slug": "gully", "concept": "Gullies and surface water inlets", "family": "services", "definition": "A trapped opening at ground level where water enters a drain — from a downpipe, from a waste pipe, or from the surface — with a water seal that stops drain air coming back out of it.", "url": "https://craftquantities.com/glossary/gully/", "names": [ { "market": "UK", "term": "gully", "alsoCalled": [ "gulley", "back inlet gully", "yard gully", "road gully", "trapped gully" ], "exactness": "close", "note": "One word covering several fittings. A BACK INLET gully takes a waste or rainwater pipe below the grating; a road gully is a much larger chambered unit with a silt bucket." }, { "market": "AU", "term": "gully", "alsoCalled": [ "gully trap", "surface inlet pit", "overflow relief gully" ], "exactness": "close", "note": "The overflow relief gully is an Australian particularity with no British equivalent: a deliberately low, easily lifted grating outside the house so that a blocked drain surcharges into the garden rather than through a shower waste." }, { "market": "US", "term": "area drain", "alsoCalled": [ "catch basin", "yard drain", "trench drain", "floor drain" ], "exactness": "false-friend", "note": "A CATCH BASIN has a sump BELOW the outlet to trap grit, which an ordinary British gully does not — so the two are not interchangeable, and a catch basin requires periodic emptying that a gully does not." }, { "market": "CA", "term": "catch basin", "alsoCalled": [ "area drain", "yard drain", "sump" ], "exactness": "false-friend", "note": "As the United States, with frost depth and grit from winter salting making the sump a practical necessity rather than an option." } ], "standards": [ { "market": "UK", "standard": "Approved Document H / BS EN 1253", "covers": "Foul and surface water drainage, and the classification and testing of gullies for buildings." }, { "market": "US", "standard": "IPC Chapter 11 / ASTM C913", "covers": "Storm drainage and area drain requirements, and precast concrete water and wastewater structures." } ], "calculators": [ { "slug": "sump-pit-catch-basin-calculator", "json": "https://craftquantities.com/api/v1/calculators/sump-pit-catch-basin-calculator.json" }, { "slug": "drain-pipe-slope-calculator", "json": "https://craftquantities.com/api/v1/calculators/drain-pipe-slope-calculator.json" }, { "slug": "storm-drain-slope-calculator", "json": "https://craftquantities.com/api/v1/calculators/storm-drain-slope-calculator.json" } ], "confusions": [ { "question": "What is a back inlet gully, and why does it matter which one is fitted?", "answer": "It is a gully where the incoming pipe discharges BELOW the grating, straight into the trapped chamber, rather than spilling onto the grating from above. The difference is entirely practical. A pipe discharging over an open grating is exposed to leaves and debris landing on the same grating, it splashes, and in a hard frost the flow can ice over the grating and back up. A back inlet takes the pipe under the grating so the discharge is enclosed, which is why it is normally required for a waste pipe from a kitchen or a washing machine and is the better arrangement for a rainwater downpipe. Substituting a plain gully for a specified back inlet one looks like the same item on an invoice and is a different fitting doing a worse job." }, { "question": "Is a catch basin the same as a gully?", "answer": "Close in position and different in design, and the difference is maintenance. Both sit at ground level and take surface water into a drain. A CATCH BASIN has a sump — a chamber extending below the level of the outgoing pipe — so grit, sand and leaf litter settle out and stay there instead of travelling into the system. That is valuable where road grit or winter salting loads the runoff, and it is a liability if nobody ever empties it, because a full sump stops catching anything and eventually stagnates. A typical British domestic gully has no such sump: the trap holds a water seal and the flow carries debris through. So a drawing calling for catch basins is calling for a structure with a maintenance schedule, not just a grating." }, { "question": "Why does a gully smell, and why is that not usually the gully's fault?", "answer": "Because the water seal has gone, and the commonest reason is that nothing has run into it. A gully's trap holds a small volume of water against drain air, and that water evaporates — so a gully serving a downpipe in a long dry spell, or one serving a waste pipe from an appliance nobody uses, loses its seal in weeks and becomes an open hole into the drain. The fix is to pour water into it, and if it smells again within days the problem is different: either the trap is damaged, or the drain itself is surcharging and pushing air up. The second diagnostic is whether nearby gullies smell too. One gully is its own trap; several at once is the system, and that is a blockage rather than a seal." } ], "related": [ "trap", "fall" ] }, { "slug": "trickle-vent", "concept": "Trickle vents and background ventilation", "family": "envelope", "definition": "A small permanent, usually closable opening through a window frame or the wall beside it, providing a continuous low rate of air exchange independent of opening the window.", "url": "https://craftquantities.com/glossary/trickle-vent/", "names": [ { "market": "UK", "term": "trickle vent", "alsoCalled": [ "background ventilator", "night vent", "slot vent" ], "exactness": "absent", "note": "Required in most new and replacement windows, sized in equivalent area in square millimetres per room, and the commonest reason a replacement window job needs more than a like-for-like swap." }, { "market": "AU", "term": "trickle vent", "alsoCalled": [ "window vent", "background ventilator" ], "exactness": "close", "note": "Present in the vocabulary and far less commonly required, since the climate and the construction tradition lean on openable windows and on mechanical extract." }, { "market": "US", "term": "(no common term)", "alsoCalled": [ "window vent", "fresh air vent" ], "exactness": "absent", "note": "Not part of standard practice. Background ventilation is delivered by a mechanical system — an exhaust fan running continuously, or a balanced ERV or HRV — and the envelope is sealed rather than deliberately perforated." }, { "market": "CA", "term": "(no common term)", "alsoCalled": [ "make-up air inlet", "passive inlet" ], "exactness": "absent", "note": "As the United States, with balanced mechanical ventilation effectively mandatory in new housing, so a passive hole in the window is contrary to the design intent." } ], "standards": [ { "market": "UK", "standard": "Approved Document F / BS EN 13141-1", "covers": "Means of ventilation, including background ventilator equivalent areas per room, and the performance testing of externally and internally mounted air transfer devices." }, { "market": "US", "standard": "ASHRAE 62.2", "covers": "Ventilation and acceptable indoor air quality in residential buildings, delivered mechanically rather than by envelope openings." } ], "calculators": [ { "slug": "rain-screen-ventilation-area-calculator", "json": "https://craftquantities.com/api/v1/calculators/rain-screen-ventilation-area-calculator.json" }, { "slug": "air-changes-per-hour-calculator", "json": "https://craftquantities.com/api/v1/calculators/air-changes-per-hour-calculator.json" }, { "slug": "cfm-ventilation-calculator", "json": "https://craftquantities.com/api/v1/calculators/cfm-ventilation-calculator.json" } ], "confusions": [ { "question": "Why does Britain put holes in its windows when everyone else seals them?", "answer": "Because the two traditions answered the same question with different technology. As houses were draughtproofed, the incidental air exchange that had always removed moisture disappeared, and something had to replace it. North American practice replaced it with a MECHANICAL system — continuous extract, or a balanced heat recovery unit — and sealed the envelope so that system is actually in control of the air. British practice replaced it with controllable PASSIVE openings, distributed through the rooms, backed by intermittent extract in the wet rooms. Each is coherent on its own terms. The failure mode is mixing them: a British house that has been sealed up without background ventilators has no path at all, which is the condensation and mould complaint in a great many modern homes, and it is also why fitting an extractor fan without providing replacement air does not fix it." }, { "question": "What is equivalent area, and why not just state the hole size?", "answer": "Because the hole size does not tell you how much air passes through it. A ventilator is not an open aperture: it has a grille, a hood, an insect mesh, a closing flap and a path with bends in it, and each of those resists flow. EQUIVALENT AREA is the measured answer — the area of a sharp-edged orifice that would pass the same airflow at the same pressure difference — so it is a performance figure derived from a test rather than a dimension read off a drawing. That is why a ventilator's equivalent area is always smaller than its visible slot, why two products of the same apparent size can differ substantially, and why a specification states equivalent area in square millimetres per room rather than naming a product. Substituting a similar-looking vent is a change to the ventilation of the room." }, { "question": "Do they make the house cold, and should they be taped shut?", "answer": "They cost a little heat and closing them costs more than that. The airflow through background ventilators is small — the design intent is a continuous trickle, not a draught — and its heat cost is real but modest against the heat lost through the glass beside it. What closing them costs is the moisture path: the water vapour a household generates has to leave, and if it cannot leave through the ventilators it leaves by condensing on the coldest surface available, which is usually a window reveal, an external wall corner or a cold bridge. So a taped-over vent is very often the hidden cause of a mould complaint on the wall next to it. The correct response to a vent that feels draughty is usually to close its flap in the coldest weather and open it again, which is what the flap is for." } ], "related": [ "cavity-wall", "conservatory", "airtightness" ] }, { "slug": "dpm", "concept": "Damp-proof membrane under a floor", "family": "envelope", "definition": "A continuous impermeable sheet laid horizontally beneath or within a ground-bearing floor, stopping moisture rising out of the ground into the slab and into whatever is laid on it.", "url": "https://craftquantities.com/glossary/dpm/", "names": [ { "market": "UK", "term": "DPM", "alsoCalled": [ "damp-proof membrane", "visqueen", "polythene", "radon barrier" ], "exactness": "false-friend", "note": "Not the same as a DPC, which is the horizontal strip in a WALL. The two must be lapped together or the floor and the wall each stop moisture and hand it to the other." }, { "market": "AU", "term": "vapour barrier", "alsoCalled": [ "under-slab membrane", "damp-proof membrane", "builder's film" ], "exactness": "close", "note": "Named as a vapour barrier despite being the same under-slab polythene, with a specified thickness and a termite-resistance requirement in much of the country." }, { "market": "US", "term": "vapor barrier", "alsoCalled": [ "vapor retarder", "under-slab membrane", "poly", "capillary break" ], "exactness": "false-friend", "note": "VAPOR RETARDER in a wall or roof is a permeance class controlling diffusion in a breathing assembly. Under a slab the sheet is stopping LIQUID and capillary moisture, which is a different mechanism with a different failure mode." }, { "market": "CA", "term": "vapour barrier", "alsoCalled": [ "under-slab poly", "air/vapour barrier", "moisture barrier" ], "exactness": "false-friend", "note": "As the United States, and the wall-side confusion is sharper because Canadian practice specifies a continuous air/vapour barrier in the wall by name." } ], "standards": [ { "market": "UK", "standard": "BS 8102 / BS 8215 / Approved Document C", "covers": "Protection against water from the ground, and the placing of damp-proof courses and membranes." }, { "market": "US", "standard": "ASTM E1745 / ACI 302.2R", "covers": "Plastic water vapor retarders used in contact with soil under concrete slabs, and guidance on slabs receiving moisture-sensitive flooring." } ], "calculators": [ { "slug": "vapor-barrier-calculator", "json": "https://craftquantities.com/api/v1/calculators/vapor-barrier-calculator.json" }, { "slug": "under-slab-seam-tape-calculator", "json": "https://craftquantities.com/api/v1/calculators/under-slab-seam-tape-calculator.json" }, { "slug": "under-slab-perimeter-foam-calculator", "json": "https://craftquantities.com/api/v1/calculators/under-slab-perimeter-foam-calculator.json" } ], "confusions": [ { "question": "What is the difference between a DPM and a DPC?", "answer": "Which plane they sit in, and they only work as a pair. A DPC is a horizontal strip built into a WALL, usually a couple of courses above external ground level, stopping moisture climbing the wall by capillary action. A DPM is a horizontal SHEET under or within the ground floor, stopping moisture rising through the slab. Each protects its own element and hands the problem to the other at the junction — so the DPM has to be lapped and sealed to the DPC around the whole perimeter, and a building where both are present but not joined has a continuous gap at the wall-floor line, which is precisely where damp appears. It is the commonest defect in a retrofitted floor: a perfect membrane over the whole slab, dressed up the wall and stopped, with nothing lapping it to the wall's own barrier." }, { "question": "Does it go above or below the slab?", "answer": "Either, and the choice changes what else has to be right. BELOW the slab, on sand blinding over the hardcore, is the common arrangement: the membrane protects the concrete itself as well as everything above it, and the blinding exists specifically to stop the stones puncturing it. ABOVE the slab, under a screed, protects the finish but leaves the slab permanently wet from below, which matters if anything in it can corrode and matters a great deal for drying time. The version that causes most trouble is a sandwich — a membrane above and below with concrete between — because the slab then has no route to dry in either direction, and a screed or a floor covering laid on it is being laid on a slab that will never reach the moisture content the adhesive assumes." }, { "question": "Why do membranes fail when the material itself is waterproof?", "answer": "Because a membrane is a system of laps and penetrations, and the sheet is the part least likely to fail. The classic failures are all at the edges: a lap not taped or not wide enough, a service pipe passing through with nothing sealing around it, a column base, a stanchion, a drain. The second family is mechanical: a sheet laid straight onto coarse hardcore is punctured by the stones under foot traffic and under the weight of the pour, which is why a sand blinding layer is specified beneath it and why walking a barrow across an unprotected membrane is a real risk rather than a fussy rule. And the third is thickness — a membrane specified at a gauge for the loading it will see, substituted with thinner polythene because it looks the same on the roll." } ], "related": [ "dpc", "vapour-control-layer" ] }, { "slug": "chipboard", "concept": "Chipboard and particleboard", "family": "materials", "definition": "A panel pressed from wood particles bonded with resin. The grades differ enormously in what they tolerate — ordinary board disintegrates when wet, and the flooring and moisture-resistant grades are a different specification rather than the same board treated.", "url": "https://craftquantities.com/glossary/chipboard/", "names": [ { "market": "UK", "term": "chipboard", "alsoCalled": [ "particle board", "flooring grade", "P5", "moisture-resistant chipboard" ], "exactness": "close", "note": "Graded P1 to P7 under BS EN 312. Domestic flooring is normally P5, which is moisture-resistant and tongue-and-grooved; the grade is what matters and the word does not carry it." }, { "market": "AU", "term": "particleboard", "alsoCalled": [ "chipboard", "structural flooring", "yellow tongue" ], "exactness": "close", "note": "Yellow tongue names the flooring grade by the colour of its tongue — a genuinely useful convention, since it identifies the grade at a glance on site in a way a British board does not." }, { "market": "US", "term": "particleboard", "alsoCalled": [ "chipboard", "PB", "underlayment" ], "exactness": "false-friend", "note": "Mostly a furniture and shelving material. American subfloors are overwhelmingly OSB or plywood, so a specification calling for particleboard underfoot reads as an error rather than a grade choice." }, { "market": "CA", "term": "particleboard", "alsoCalled": [ "chipboard", "MDF core", "underlayment" ], "exactness": "false-friend", "note": "As the United States, with OSB the default sheathing and subfloor material." } ], "standards": [ { "market": "UK", "standard": "BS EN 312 / BS EN 13986", "covers": "Particleboard grades P1 to P7 and their requirements, and wood-based panels for use in construction." }, { "market": "US", "standard": "ANSI A208.1 / APA rated sheathing", "covers": "Particleboard grades for industrial and furniture use, and the panel ratings that govern structural sheathing instead." } ], "calculators": [ { "slug": "plywood-sheet-calculator", "json": "https://craftquantities.com/api/v1/calculators/plywood-sheet-calculator.json" }, { "slug": "floor-underlayment-roll-calculator", "json": "https://craftquantities.com/api/v1/calculators/floor-underlayment-roll-calculator.json" }, { "slug": "access-floor-panel-count-calculator", "json": "https://craftquantities.com/api/v1/calculators/access-floor-panel-count-calculator.json" } ], "confusions": [ { "question": "Is all chipboard the same thing in different thicknesses?", "answer": "No, and it is the assumption behind most chipboard failures. The European grading runs from P1, a general-purpose board for dry interior use, up through P5, which is load-bearing and moisture-resistant, to P7 for heavy-duty humid conditions. They look similar on a stack and behave nothing alike: ordinary board exposed to water swells irreversibly, loses its strength, and does not recover when it dries — the particles have been pushed apart and the resin bond is gone. P5 flooring board is made with a different resin system and is dimensionally far more stable when wet, which is why it survives a building being closed in and why a bathroom floor in the wrong grade fails around the WC and the bath within a few years. The grade is printed on the board; it is worth reading." }, { "question": "Why does a chipboard floor squeak and dip at the joints when plywood does not?", "answer": "Because of how the panel carries load at its edge and what holds the edge down. Chipboard flooring is tongue-and-grooved so that adjacent boards support each other along their long edges, and that joint depends on being glued: the specification is to glue the tongue, not merely to push it home. Left unglued, the edge relies on the tongue alone, and the repeated flexing of two boards moving independently wears the joint, dips under foot and squeaks. The second factor is the fixing — chipboard's screw-holding is weaker than plywood's, so a screw that is overdriven strips its own hole and the board lifts back onto it. The practical consequences are that chipboard flooring is a glued-and-screwed installation rather than a nailed one, and that a squeaky chipboard floor is rarely fixed by adding screws in the same places." }, { "question": "Chipboard, MDF or OSB — what actually decides?", "answer": "Particle size and where the strength comes from, which sends each to a different job. CHIPBOARD is pressed from relatively large flakes and chips, giving reasonable stiffness across a panel and mediocre edges. MDF is milled to fibres and pressed to a uniform density, so it has no grain and a machinable edge — which is why it takes a moulded profile and a painted finish and why it is the joinery and moulding material. OSB is made from long strands laid in oriented layers, so it behaves far more like a structural panel and is what carries load in a North American wall or roof. Asking chipboard to do OSB's job underfoot in a wet area, or MDF's job on a moulded edge, is the usual way each of them disappoints." } ], "related": [ "osb" ] }, { "slug": "snagging", "concept": "Snagging and the punch list", "family": "site", "definition": "The stage at the end of a job where the remaining defects and incomplete items are identified, listed, and worked through before the job is accepted as complete.", "url": "https://craftquantities.com/glossary/snagging/", "names": [ { "market": "UK", "term": "snagging", "alsoCalled": [ "snag list", "snags", "defects list", "de-snagging" ], "exactness": "close", "note": "Commonly done by the buyer or an independent inspector on a new home, which is why a British snagging list arrives from OUTSIDE the contract rather than from the contractor's own inspection." }, { "market": "AU", "term": "defects list", "alsoCalled": [ "snag list", "practical completion inspection", "PCI" ], "exactness": "close", "note": "The inspection is named for the contract milestone rather than the list, and the PCI is a scheduled event with its own rights attached." }, { "market": "US", "term": "punch list", "alsoCalled": [ "punchlist", "punch out", "deficiency list" ], "exactness": "close", "note": "Traditionally generated by the architect or owner's representative walking the job at substantial completion, and the list is a contract instrument tied to the release of retainage." }, { "market": "CA", "term": "deficiency list", "alsoCalled": [ "punch list", "deficiencies", "takeover inspection" ], "exactness": "close", "note": "Deficiency is the standard contract word, with punch list understood from American usage." } ], "standards": [ { "market": "UK", "standard": "JCT contracts / NHBC standards", "covers": "Practical completion, the rectification period, and the tolerances a new home is judged against." }, { "market": "US", "standard": "AIA A201", "covers": "Substantial completion, the punch list procedure, and the withholding and release of retainage against it." } ], "calculators": [ { "slug": "project-contingency-calculator", "json": "https://craftquantities.com/api/v1/calculators/project-contingency-calculator.json" }, { "slug": "cost-per-square-foot-calculator", "json": "https://craftquantities.com/api/v1/calculators/cost-per-square-foot-calculator.json" }, { "slug": "material-waste-cost-calculator", "json": "https://craftquantities.com/api/v1/calculators/material-waste-cost-calculator.json" } ], "confusions": [ { "question": "Is a snag list the same as a punch list?", "answer": "The stage is the same and the authorship usually is not, which is where cross-market jobs go wrong. An American punch list is traditionally produced BY the design team or the owner's representative at substantial completion, and it is a contract instrument: it defines what remains before final payment and the release of retainage. A British snagging list, particularly on a new home, is frequently produced by the BUYER or an inspector they engaged, and it has no automatic contractual standing at all — the developer's own inspection is the one the contract refers to. So the two documents can describe the same building and carry completely different weight, and a party assuming their own convention will either over-estimate or under-estimate what their list obliges anybody to do." }, { "question": "What is the difference between a snag and a defect?", "answer": "Timing and severity, and the two lead to different remedies. A SNAG is an item outstanding at completion — something not finished, not adjusted, or damaged during the works — and the expectation is that it is put right as part of finishing the job. A DEFECT is something that fails after the job is accepted, during whatever period the contract or the warranty runs, and the remedy usually sits with a different obligation and sometimes a different party: the contractor under a rectification period, or a structural warranty provider for items beyond it. Listing a defect as a snag under-states it; listing a snag as a defect delays it until after completion when the trades have left. On a new home the distinction also decides which body a complaint goes to." }, { "question": "What actually belongs on the list, and what does not?", "answer": "Departures from the specification and from the stated tolerances — not departures from what somebody hoped for. That is the most useful thing to know before writing one, because a list that mixes the two loses its force: the recipient works through the items that are plainly wrong, disputes the ones that are matters of taste, and the whole document becomes negotiable. Standards bodies publish tolerances precisely so this argument has an answer — how far out of plumb a wall may be, how much a floor may deviate over a given length, how visible a plaster blemish may be under normal lighting rather than under a raking lamp. A list that cites the tolerance it says has been exceeded is a different document from one that says a wall looks uneven." } ], "related": [ "skip" ] }, { "slug": "coping", "concept": "Coping and capping", "family": "envelope", "definition": "The unit laid along the top of a free-standing or parapet wall to shed water off it. A coping projects beyond both faces and throws water clear; a capping sits flush and does not.", "url": "https://craftquantities.com/glossary/coping/", "names": [ { "market": "UK", "term": "coping", "alsoCalled": [ "coping stone", "capping", "cope", "wall coping" ], "exactness": "false-friend", "note": "A COPING overhangs both faces with a drip; a CAPPING is flush. The words are used interchangeably in speech and are not the same detail. And in carpentry a cope is a scribed cut, not a component." }, { "market": "AU", "term": "capping", "alsoCalled": [ "coping", "wall capping", "pool coping" ], "exactness": "close", "note": "Capping is the more common term for a wall top, with coping reserved more often for the pool edge." }, { "market": "US", "term": "coping", "alsoCalled": [ "cap", "wall cap", "parapet coping", "pool coping" ], "exactness": "false-friend", "note": "Pool coping is the commonest use of the word in domestic American English and means the edge trim around a swimming pool, not a wall capping. In carpentry, to cope a joint is to scribe one moulding to fit another's profile." }, { "market": "CA", "term": "coping", "alsoCalled": [ "wall cap", "parapet cap", "cap flashing" ], "exactness": "close", "note": "As the United States, with metal cap flashing over a parapet a distinct component specified alongside the masonry coping." } ], "standards": [ { "market": "UK", "standard": "BS 5642-2 / Approved Document C", "covers": "Copings of precast concrete, cast stone, clayware, slate and natural stone, and resistance to moisture." }, { "market": "US", "standard": "IBC 1503.3 / SMACNA Architectural Sheet Metal Manual", "covers": "Parapet coping requirements, and the detailing of metal copings and cap flashings." } ], "calculators": [ { "slug": "coping-cap-calculator", "json": "https://craftquantities.com/api/v1/calculators/coping-cap-calculator.json" }, { "slug": "seat-wall-concrete-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/seat-wall-concrete-volume-calculator.json" }, { "slug": "retaining-wall-block-calculator", "json": "https://craftquantities.com/api/v1/calculators/retaining-wall-block-calculator.json" } ], "confusions": [ { "question": "What is the difference between a coping and a capping, and does it matter?", "answer": "The overhang, and it matters more than almost any other detail on a free-standing wall. A COPING projects beyond both faces of the wall and has a drip groove or a weathered profile underneath, so rain running off it falls clear rather than tracking back onto the wall face. A CAPPING sits flush with the wall, so the water runs straight down the face — which saturates the masonry immediately below the top, and that band is the first part of any wall to fail by freeze-thaw. On a garden wall the difference shows up as a strip of eroded mortar and spalled brick along the top few courses. A capping is not wrong in itself; it is a choice that puts the water on the wall, and the wall then has to be built to take it." }, { "question": "Why does a coping need a damp-proof course under it?", "answer": "Because the top of a wall is the one place water can get in from ABOVE, and a free-standing wall has no roof to stop it. Rain lands on the coping, works into the joints between coping units, and travels down into the masonry — where, with no way out and no way to dry from both sides quickly, it saturates and then freezes. A DPC bedded under the coping intercepts that, which is why it is specified even on garden walls that are otherwise unremarkable, and why the DPC has to be continuous through the joints rather than stopped at each unit. The other half of the detail is the joints in the coping themselves: they are the weak point, which is why copings are bedded and pointed carefully and why a cracked coping joint is a genuine defect rather than a cosmetic one." }, { "question": "What does coping mean in carpentry?", "answer": "A cut, not a component, and it is the better way to join two mouldings at an internal corner. A mitred internal corner puts two angled cuts against each other, and because timber moves and no corner is exactly square, that joint opens. A COPED joint instead leaves one piece running straight into the corner and scribes the second piece to the first one's profile, so it sits against the moulded face rather than against another cut end — the joint closes on itself as the timber moves, and a slightly out-of-square corner is absorbed rather than exposed. It is why skirting and coving are coped at internal angles and mitred only at external ones, and why a coping saw is called that." } ], "related": [ "dpc" ] }, { "slug": "stud", "concept": "Stud and framed partition", "family": "structure", "definition": "The vertical member in a framed wall, spanning between a bottom and a top plate and carrying the wall's covering — and, in a loadbearing wall, the floor or roof above.", "url": "https://craftquantities.com/glossary/stud/", "names": [ { "market": "UK", "term": "stud", "alsoCalled": [ "stud wall", "timber frame", "partition", "CLS", "metal stud" ], "exactness": "false-friend", "note": "Stud wall is used for the whole partition, so a quantity of studs and a quantity of stud wall are different things. A stud is also a threaded bar and a fixing, both of which appear on the same drawing." }, { "market": "AU", "term": "stud", "alsoCalled": [ "wall frame", "noggin", "top plate", "bottom plate" ], "exactness": "close", "note": "As the UK, with the framing usually supplied as prefabricated wall frames rather than cut on site, so the stud is a component of a delivered panel." }, { "market": "US", "term": "stud", "alsoCalled": [ "2x4", "2x6", "king stud", "jack stud", "cripple" ], "exactness": "close", "note": "The framing vocabulary is far more differentiated: king, jack, cripple and trimmer name a stud by its role at an opening, and British usage has no standard word for most of them." }, { "market": "CA", "term": "stud", "alsoCalled": [ "2x4", "2x6", "wall stud", "trimmer" ], "exactness": "close", "note": "As the United States, with 2x6 exterior walls far more common because the insulation depth is driven by a colder design temperature." } ], "standards": [ { "market": "UK", "standard": "BS EN 1995-1-1 / BS 8212", "covers": "Design of timber structures, and code of practice for dry lining and partitioning with gypsum board." }, { "market": "US", "standard": "IRC R602 / AWC NDS", "covers": "Wood wall framing, stud size and spacing tables by storey and loading, and the national design specification for wood construction." } ], "calculators": [ { "slug": "framing-stud-calculator", "json": "https://craftquantities.com/api/v1/calculators/framing-stud-calculator.json" }, { "slug": "stud-calculator", "json": "https://craftquantities.com/api/v1/calculators/stud-calculator.json" }, { "slug": "curved-wall-stud-layout-calculator", "json": "https://craftquantities.com/api/v1/calculators/curved-wall-stud-layout-calculator.json" }, { "slug": "cfs-stud-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/cfs-stud-spacing-calculator.json" }, { "slug": "cfs-stud-deflection-calculator", "json": "https://craftquantities.com/api/v1/calculators/cfs-stud-deflection-calculator.json" } ], "confusions": [ { "question": "Why is a 2x4 not two inches by four?", "answer": "Because it was, before it was planed. Timber is sawn to the nominal size green and then dried and surfaced, and both take material off — so a nominal 2x4 finishes at about 1½ by 3½ inches, a 2x6 at 1½ by 5½, and the nominal figure survives as a name rather than a measurement. British practice has the same phenomenon with an extra wrinkle: timber is sold both SAWN and PLANED, and a 'four by two' regularised for framing is typically around 38 by 89 mm — which is the same finished section as an American 2x4 by a different route, since 38 by 89 is 1½ by 3½ inches converted. So the two markets nominally disagree and physically arrive at the same stick. What does not travel is the assumption: a specification quoting a nominal size has not stated a dimension, and a specification quoting millimetres usually has." }, { "question": "What are king, jack and cripple studs, and what does British practice call them?", "answer": "They are studs named by their job at an opening, and British practice mostly has no equivalent words. A KING stud runs full height beside an opening; a JACK or trimmer stud is the shorter one nailed to it that carries the header or lintel; a CRIPPLE is a short stud above a header or below a sill, filling the gap at the normal spacing so the covering still has a fixing. British drawings tend to describe the same arrangement geometrically — a full-height stud each side with a trimmer under the lintel and short studs over — without naming the members. The consequence when reading American framing guidance is that the count matters: a specification calling for two jacks each side is calling for four extra studs per opening, and that is not a detail a British take-off derived from a stud spacing will have picked up." }, { "question": "Why is stud spacing 400 or 600 mm rather than anything else?", "answer": "Because the BOARD decides it, not the stud. Plasterboard and sheathing come in fixed widths — 1200 mm, or 4 feet — and every sheet edge has to land on a member. Divide 1200 by 400 and you get exactly three bays with an edge on a stud at each end; divide by 600 and you get two. That is the whole reason those two numbers dominate: they are the divisors of the sheet, and 16 and 24 inches are the same two numbers in the other system. The structural question — whether a stud of a given size can carry the load at that spacing — is then checked against the spacing the boards imposed, rather than the other way round. It is also why a non-standard spacing costs more in board than it saves in timber: every sheet needs cutting and the offcut is usually waste." } ], "related": [ "noggin" ] }, { "slug": "brick-bond", "concept": "Brickwork bond", "family": "structure", "definition": "The pattern in which bricks are laid so that vertical joints do not line up between courses. In a solid wall the bond also ties the wall's thickness together; in a single-leaf wall it is a pattern and nothing more.", "url": "https://craftquantities.com/glossary/brick-bond/", "names": [ { "market": "UK", "term": "bond", "alsoCalled": [ "stretcher bond", "English bond", "Flemish bond", "header bond" ], "exactness": "false-friend", "note": "A STRETCHER is a brick laid lengthways; a HEADER is one laid with its end showing. That is the original sense of header, and it is why the American use of the word for a lintel collides so badly here." }, { "market": "AU", "term": "bond", "alsoCalled": [ "stretcher bond", "running bond", "Flemish bond" ], "exactness": "close", "note": "British names in specifications, with running bond understood from American usage in everyday speech." }, { "market": "US", "term": "bond", "alsoCalled": [ "running bond", "common bond", "American bond", "stack bond" ], "exactness": "close", "note": "RUNNING bond is the British stretcher bond. COMMON or American bond is stretcher courses with a header course at intervals, which British usage does not have as a single named pattern." }, { "market": "CA", "term": "bond", "alsoCalled": [ "running bond", "stack bond", "Flemish bond" ], "exactness": "close", "note": "As the United States, with stack bond — no overlap at all — used decoratively and requiring reinforcement in the joints because it has no bond in the structural sense." } ], "standards": [ { "market": "UK", "standard": "BS EN 1996-1-1 / PD 6697", "covers": "Design of masonry structures, and recommendations for bonding, overlap and the strength that depends on it." }, { "market": "US", "standard": "TMS 402 / ASTM C216", "covers": "Masonry design including bond patterns and joint reinforcement for stack bond, and facing brick specification." } ], "calculators": [ { "slug": "brick-calculator", "json": "https://craftquantities.com/api/v1/calculators/brick-calculator.json" }, { "slug": "masonry-bond-beam-rebar-calculator", "json": "https://craftquantities.com/api/v1/calculators/masonry-bond-beam-rebar-calculator.json" }, { "slug": "masonry-control-joint-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/masonry-control-joint-spacing-calculator.json" }, { "slug": "masonry-prism-ht-ratio-calculator", "json": "https://craftquantities.com/api/v1/calculators/masonry-prism-ht-ratio-calculator.json" } ], "confusions": [ { "question": "What does a header actually do, and why is only one market's word for it ambiguous?", "answer": "In brickwork a header is a brick laid with its short end showing on the face, and in a solid wall it is laid ACROSS the thickness, tying the front of the wall to the back. That is what bonding a solid wall means: without headers the two faces are two separate skins standing beside each other, and the wall is far weaker than the sum of them. The word travelled into American framing to mean the beam over an opening, which is a completely different member — and that is why a British reader meeting header on an American drawing has to check which is meant. On a British drawing header means the brick, and a header tank is a cistern, and a header in pipework is a manifold. None of them spans an opening." }, { "question": "Can you tell a solid wall from a cavity wall by looking at the bond?", "answer": "Usually, and it is the fastest external clue there is. A cavity wall's outer leaf is a single brick thick, so it can only be laid in stretchers — every brick lengthways, every course offset by half — which is stretcher or running bond. A solid wall has to be tied through its thickness, so it shows HEADERS: English bond alternates whole courses of stretchers and headers, Flemish bond alternates stretcher and header within each course. So a brick elevation showing no header bricks anywhere is almost certainly a cavity wall, and one showing a regular pattern of short brick ends is almost certainly solid. It is not infallible — snapped headers can be used decoratively on a cavity wall — but it is the first thing to look at, and it changes what can be assumed about insulation, damp and fixing into the wall." }, { "question": "Why does stack bond need reinforcement when other bonds do not?", "answer": "Because it has no overlap, so it is not bonded at all in the structural sense. Every other pattern offsets the vertical joints between courses, which forces a crack or a load to travel a longer, interrupted path and lets the wall distribute stress sideways. Stack bond puts every vertical joint directly above the last, creating continuous unbroken lines from bottom to top — a ready-made crack path — and each column of bricks is effectively independent of the ones beside it. Codes respond by requiring reinforcement in the bed joints to do the job the overlap would have done. It is a useful illustration of what bond is FOR: the pattern is not decoration that happens to be structural, it is structure that happens to be visible." } ], "related": [ "lintel", "frog", "engineering-brick" ] }, { "slug": "weep-hole", "concept": "Weep holes and cavity drainage", "family": "envelope", "definition": "Deliberate openings at the base of a cavity, and above every tray or obstruction within it, letting water that has crossed the outer leaf escape back out instead of collecting.", "url": "https://craftquantities.com/glossary/weep-hole/", "names": [ { "market": "UK", "term": "weep hole", "alsoCalled": [ "open perpend", "weep vent", "perp vent" ], "exactness": "close", "note": "Usually formed by leaving a perpend — the vertical joint between bricks — unmortared, often with a plastic weep vent inserted to keep insects out while passing water." }, { "market": "AU", "term": "weephole", "alsoCalled": [ "weep vent", "open perp", "vermin-proof weep" ], "exactness": "close", "note": "As the UK, with vermin-proofing a standard requirement rather than an option." }, { "market": "US", "term": "weep hole", "alsoCalled": [ "weep", "rope weep", "tube weep", "weep screed" ], "exactness": "false-friend", "note": "WEEP SCREED is a different component: a perforated metal profile at the base of a stucco wall forming both a stop for the render and a drainage path. It is not a hole in a brick joint." }, { "market": "CA", "term": "weep hole", "alsoCalled": [ "weep vent", "drainage opening", "weeping tile" ], "exactness": "false-friend", "note": "WEEPING TILE is the further trap — it means the perforated drain pipe around a foundation, nothing to do with a cavity wall, and the name survives from when it was made of clay tile lengths." } ], "standards": [ { "market": "UK", "standard": "Approved Document C / PD 6697", "covers": "Resistance to moisture, and recommendations for cavity trays, weep holes and their spacing." }, { "market": "US", "standard": "TMS 402 Chapter 12 / IBC 1405", "covers": "Anchored veneer drainage requirements, weep spacing, and the flashing that has to accompany them." } ], "calculators": [ { "slug": "cavity-wall-weep-hole-calculator", "json": "https://craftquantities.com/api/v1/calculators/cavity-wall-weep-hole-calculator.json" }, { "slug": "stone-veneer-weep-screed-calculator", "json": "https://craftquantities.com/api/v1/calculators/stone-veneer-weep-screed-calculator.json" }, { "slug": "wall-tie-density-calculator", "json": "https://craftquantities.com/api/v1/calculators/wall-tie-density-calculator.json" } ], "confusions": [ { "question": "Why does a wall need holes in it on purpose?", "answer": "Because a cavity wall is designed to let the outer leaf get wet. Brickwork is not waterproof — driving rain passes through it — and the cavity's job is to catch that water on the inside face of the outer leaf and give it somewhere to go. Without an escape at the bottom, the water runs down and collects on whatever stops it: the base of the cavity, a cavity tray, a lintel, the top of a floor slab. It then stands there, saturates the masonry around it, and eventually finds the inner leaf. Weep holes are the exit. That is why they appear not only at the base of the wall but immediately above every tray and every obstruction — because each of those is a new floor for the water and each needs its own way out." }, { "question": "What happens when they get blocked, and how do you tell?", "answer": "The cavity fills, and the symptom shows up somewhere that looks unrelated. Weeps get blocked by mortar droppings during construction, by pointing done later, by render or paint applied over the elevation, by insects nesting, and by ground level being raised against the wall. Once blocked, water standing in the cavity above a tray finds the inner leaf, and the damp appears internally at that level — commonly above a window, which is where a tray sits. The diagnostic is that the damp is at a consistent HEIGHT rather than rising from the floor or coming from above, and the check is to look for open perpends at that level outside and see whether they are clear. Poking one open often produces water immediately." }, { "question": "Is a weep screed the same thing?", "answer": "No — same purpose, different component, different wall. A weep screed is a perforated metal profile fixed along the BOTTOM of a stucco or render wall, usually over a framed structure. It does three things at once: it stops the render at a clean line, it holds the render off the foundation so water cannot wick up into it, and its perforations drain the drainage plane behind the render. So it is a manufactured trim, installed once along a length, rather than a set of openings left in masonry joints. The confusion matters when reading an American detail on a British wall: a specification calling for a weep screed is calling for a product to be ordered by the metre, not for perpends to be left open." } ], "related": [ "cavity-wall", "cavity-tray" ] }, { "slug": "padstone", "concept": "Padstone and bearing plate", "family": "structure", "definition": "A block of concrete, stone or steel placed under the end of a beam to spread its reaction over enough masonry that the masonry is not crushed. It does nothing for the beam; it protects what the beam sits on.", "url": "https://craftquantities.com/glossary/padstone/", "names": [ { "market": "UK", "term": "padstone", "alsoCalled": [ "pad stone", "bearing pad", "spreader", "template" ], "exactness": "close", "note": "Normally a precast concrete block of a size the structural engineer states, and its dimensions are a calculation rather than a standard item — a beam schedule gives the padstone with the beam." }, { "market": "AU", "term": "padstone", "alsoCalled": [ "bearing pad", "spreader plate", "engaged pier" ], "exactness": "close", "note": "As the UK, with an engaged pier — a thickening of the wall under the bearing — used as an alternative where the load is high." }, { "market": "US", "term": "bearing plate", "alsoCalled": [ "beam pocket", "bond beam", "steel bearing plate", "column cap" ], "exactness": "false-friend", "note": "There is no single standard word. The equivalent is a steel bearing plate, a filled and reinforced bond beam under the bearing, or a formed beam pocket — and a BASEPLATE is a different component at the BOTTOM of a column." }, { "market": "CA", "term": "bearing plate", "alsoCalled": [ "beam seat", "bond beam", "lintel bearing" ], "exactness": "false-friend", "note": "As the United States, with beam seat used where British practice would say bearing." } ], "standards": [ { "market": "UK", "standard": "BS EN 1996-1-1 / PD 6697", "covers": "Design of masonry including concentrated loads, bearing areas and the local compressive stress under a beam end." }, { "market": "US", "standard": "TMS 402 Chapter 5 / AISC 360", "covers": "Concentrated loads on masonry and the distribution area assumed, and bearing plate design for steel members." } ], "calculators": [ { "slug": "lintel-bearing-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/lintel-bearing-length-calculator.json" }, { "slug": "footing-bearing-pressure-calculator", "json": "https://craftquantities.com/api/v1/calculators/footing-bearing-pressure-calculator.json" }, { "slug": "steel-baseplate-bearing-calculator", "json": "https://craftquantities.com/api/v1/calculators/steel-baseplate-bearing-calculator.json" } ], "confusions": [ { "question": "Why does a beam need a padstone when the wall is already strong?", "answer": "Because the wall's strength is quoted over an area and the beam delivers its whole reaction to a very small one. A masonry wall might safely carry several newtons per square millimetre spread out, and a steel beam bearing 150 mm onto a 100 mm wide wall is applying its entire end reaction through 15,000 square millimetres — which for a beam carrying a floor and a roof can put the local stress far past what the masonry takes. The masonry then crushes locally, the beam end drops, and everything it carries drops with it. The padstone is a block stiff enough to spread that reaction over a larger footprint of wall, and its SIZE is the answer to that arithmetic. It is not a packing piece and it is not optional because the wall looks solid." }, { "question": "What decides how big it has to be?", "answer": "The beam's end reaction divided by what the masonry beneath can take, with the spread through the padstone allowed for. Three things move it. The LOAD — a beam removing a wall in a two-storey house has a far larger reaction than one over a garage door. The MASONRY — a dense concrete block or engineering brick takes several times the stress a lightweight aerated block does, so the same beam on a different wall needs a different padstone or a different block locally. And the BEARING LENGTH, because the padstone's own length is part of the spread. That is why a padstone appears on a structural engineer's calculation with a size, a concrete grade and sometimes reinforcement, and why substituting a convenient block from the merchant is a change to the design rather than to the shopping list." }, { "question": "Can one be added after the beam is in?", "answer": "Sometimes, and it is a great deal more work than putting it in first, which is why the omission is expensive rather than merely awkward. The bearing has to be relieved — the beam temporarily supported by props or needles taking the load past the bearing point — and then the masonry under the end cut out and the padstone built in and allowed to gain strength before the load is returned to it. That is a propping operation with its own design, in a building that is by definition already relying on the beam. It is also the reason a beam installed without its specified padstone is a genuine finding rather than a paperwork one: the wall beneath may already be crushing, and the settlement it causes will have redistributed load elsewhere before anybody notices." } ], "related": [ "rsj" ] }, { "slug": "flue", "concept": "Flue, chimney and vent", "family": "services", "definition": "The passage that carries the products of combustion from an appliance to outside. The flue is the passage; the chimney is the structure containing it; and one chimney can contain several flues.", "url": "https://craftquantities.com/glossary/flue/", "names": [ { "market": "UK", "term": "flue", "alsoCalled": [ "chimney", "flue liner", "balanced flue", "room-sealed flue" ], "exactness": "false-friend", "note": "Flue and chimney are distinguished: the flue is the passage, the chimney the structure. A VENT in British usage almost always brings air in, which is the opposite direction." }, { "market": "AU", "term": "flue", "alsoCalled": [ "chimney", "flue pipe", "cowl" ], "exactness": "close", "note": "As the UK, with flue used for the metal pipe on a stove or heater far more often than chimney." }, { "market": "US", "term": "vent", "alsoCalled": [ "flue", "chimney", "vent connector", "B-vent", "direct vent" ], "exactness": "false-friend", "note": "VENT is the standard word for a combustion outlet, which is the reverse of British usage. A direct vent appliance is the equivalent of a room-sealed balanced flue." }, { "market": "CA", "term": "vent", "alsoCalled": [ "flue", "chimney", "direct vent", "chimney liner" ], "exactness": "false-friend", "note": "As the United States, with vent used for both combustion outlets and plumbing vent stacks, which is a third meaning again." } ], "standards": [ { "market": "UK", "standard": "Approved Document J / BS EN 1443", "covers": "Combustion appliances and fuel storage systems, and the performance requirements and designation system for chimneys." }, { "market": "US", "standard": "NFPA 211 / NFPA 54", "covers": "Chimneys, fireplaces, vents and solid fuel-burning appliances, and the national fuel gas code for venting." } ], "calculators": [ { "slug": "cfm-ventilation-calculator", "json": "https://craftquantities.com/api/v1/calculators/cfm-ventilation-calculator.json" }, { "slug": "air-changes-per-hour-calculator", "json": "https://craftquantities.com/api/v1/calculators/air-changes-per-hour-calculator.json" }, { "slug": "attic-ventilation-calculator", "json": "https://craftquantities.com/api/v1/calculators/attic-ventilation-calculator.json" }, { "slug": "chimney-chase-clearance-calculator", "json": "https://craftquantities.com/api/v1/calculators/chimney-chase-clearance-calculator.json" }, { "slug": "combustion-air-free-area-calculator", "json": "https://craftquantities.com/api/v1/calculators/combustion-air-free-area-calculator.json" } ], "confusions": [ { "question": "Is a flue the same as a chimney?", "answer": "The flue is the passage and the chimney is the structure around it, and the distinction matters most on an old house. A Victorian chimney stack commonly contains several separate flues, one per fireplace, rising side by side and separated only by a brick withe — so a single chimney can be serving three rooms with three independent passages, and a blockage or a leak in one says nothing about the others. It also explains a class of problem that baffles people: smoke from one room appearing in another, which is a withe that has broken down and let two flues communicate. The American word vent sidesteps the distinction entirely by naming the function, which is clearer in a modern installation and unhelpful when discussing an existing stack." }, { "question": "What is a balanced flue, and why is it sealed from the room?", "answer": "It is a concentric arrangement that takes combustion air IN through the outer passage and sends products OUT through the inner one, so the appliance never draws air from the room it stands in — hence room-sealed. The American term is a direct vent, and it names the same thing. The reason it matters is that an open-flued appliance is in competition with the building for air: it needs a permanent air supply, it can be starved by an extractor fan, and it can spill combustion products back into the room when the house goes to negative pressure. A room-sealed appliance has neither problem, which is why it has become standard, and why a modern boiler needs no ventilation opening in the room while an older one did." }, { "question": "Why does an old chimney need lining before a stove goes in?", "answer": "Because the flue it offers is the wrong size and the wrong condition for the appliance. An open fire needed a large flue moving a large volume of relatively cool gas; a modern stove produces a much smaller volume of hotter gas, and putting it into an oversized flue means the gases cool on the way up, lose buoyancy, and deposit tar rather than leaving. That is both a draught problem and a chimney fire risk. The second reason is integrity: the mortar joints and the withes in a stack of any age are rarely gas-tight, so products can leak into adjoining flues or into rooms the chimney passes through. A liner solves both by giving the appliance a correctly sized, continuous, sealed passage — which is why liner diameter is specified by the appliance and not by the chimney." } ], "related": [ "soil-pipe" ] }, { "slug": "radiator", "concept": "Radiator and heat emitter", "family": "services", "definition": "The component in a wet heating system that transfers heat from the circulating water into the room. Despite the name, most of that transfer is convection rather than radiation.", "url": "https://craftquantities.com/glossary/radiator/", "names": [ { "market": "UK", "term": "radiator", "alsoCalled": [ "rad", "panel radiator", "convector", "towel rail" ], "exactness": "false-friend", "note": "Almost always a pressed steel panel with convector fins, on a pumped low-temperature water circuit. The name is a misnomer: a panel radiator moves most of its heat by convection." }, { "market": "AU", "term": "radiator", "alsoCalled": [ "panel heater", "hydronic radiator", "column radiator" ], "exactness": "close", "note": "Hydronic heating is a minority system, so radiator often means an electric panel heater in everyday speech rather than a wet emitter." }, { "market": "US", "term": "radiator", "alsoCalled": [ "steam radiator", "cast iron radiator", "baseboard", "register" ], "exactness": "false-friend", "note": "The word most often means a cast iron steam or hot water unit in an older building. A modern American house is more likely to have forced-air REGISTERS or hydronic BASEBOARD, neither of which is a radiator." }, { "market": "CA", "term": "radiator", "alsoCalled": [ "baseboard", "register", "hydronic radiator" ], "exactness": "false-friend", "note": "As the United States, with hydronic systems more common, so a true wet radiator is less unusual than south of the border." } ], "standards": [ { "market": "UK", "standard": "BS EN 442 / Approved Document L", "covers": "Radiator output testing and the standard temperature conditions it is quoted at, and conservation of fuel and power." }, { "market": "US", "standard": "ASHRAE Handbook — HVAC Systems and Equipment", "covers": "Hydronic and steam heating equipment, and the rating conditions for heat emitters." } ], "calculators": [ { "slug": "baseboard-heater-btu-calculator", "json": "https://craftquantities.com/api/v1/calculators/baseboard-heater-btu-calculator.json" }, { "slug": "baseboard-heater-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/baseboard-heater-length-calculator.json" }, { "slug": "hvac-thermal-load-calculator", "json": "https://craftquantities.com/api/v1/calculators/hvac-thermal-load-calculator.json" }, { "slug": "room-heat-loss-calculator", "json": "https://craftquantities.com/api/v1/calculators/room-heat-loss-calculator.json" } ], "confusions": [ { "question": "Why does a radiator's stated output not match what it delivers?", "answer": "Because the quoted figure belongs to a test condition, and almost no real system runs at it. Outputs are published at a standard temperature difference between the water and the room — commonly a mean water temperature 50 degrees above room temperature under the modern European convention, and older catalogues used a larger difference still. Run the same radiator at a lower flow temperature, which is exactly what a condensing boiler or a heat pump wants in order to be efficient, and its output falls steeply: a system designed around 75 degree flow and rerun at 45 delivers a fraction of the catalogue number. That is the single most important fact when converting a house to a heat pump — the emitters usually have to grow, and the radiator that was adequate becomes the reason the house is cold." }, { "question": "Why is it called a radiator if it mostly convects?", "answer": "History, and it is worth knowing because it explains the shape of the modern product. Early cast iron units did radiate a significant share of their heat: large surface area, high surface temperature, exposed on all sides. A modern steel panel runs cooler and gets most of its output from air being warmed at its surface, rising, and drawing cooler air in behind it — which is convection, and is why the fins welded to the back of a double-panel radiator matter so much: they add surface for the air to pass over, not surface you can see. It is also why boxing a radiator in, putting a shelf immediately above it, or standing a sofa against it costs real output: those all interfere with the air path rather than with the radiation." }, { "question": "What is the lockshield valve for, and why is one end different?", "answer": "A radiator has two valves doing two different jobs. One end is the control — a wheelhead or a thermostatic valve — which is meant to be adjusted by the occupant. The other end is the LOCKSHIELD, capped so it cannot be casually turned, and it sets how much of the system's flow this particular radiator takes. That is balancing: without it, the radiators nearest the pump take most of the flow and the far ones stay cool, regardless of how far open their control valves are. A cold radiator at the end of a run, with everything else hot, is nearly always a balancing problem rather than a fault — and it is why fitting a new pump or a new boiler to an unbalanced system does not fix it, and sometimes makes it more obvious." } ], "related": [ "hot-water-cylinder", "trv" ] }, { "slug": "eaves", "concept": "Eaves", "family": "envelope", "definition": "The lower edge of a roof, where the covering stops and water leaves it. Almost always the point where the gutter, the roof's ventilation inlet and the junction with the wall all occur within a few hundred millimetres of each other.", "url": "https://craftquantities.com/glossary/eaves/", "names": [ { "market": "UK", "term": "eaves", "alsoCalled": [ "eaves course", "overhang", "eaves soffit", "sprocket" ], "exactness": "close", "note": "A single word covering the edge, the overhang and the assembly beneath it. The eaves course of tiles is shorter than the rest and doubled, which is why an eaves count is not the same as a field count." }, { "market": "AU", "term": "eaves", "alsoCalled": [ "eave", "overhang", "eaves lining" ], "exactness": "close", "note": "Frequently singular in speech, and the overhang is a deliberate shading device sized against the sun angle rather than only a weathering detail." }, { "market": "US", "term": "eave", "alsoCalled": [ "eaves", "overhang", "drip edge", "soffit and fascia" ], "exactness": "close", "note": "The eave carries a metal DRIP EDGE and, in most of the country, a self-adhering ice-and-water membrane for a stated distance up the slope — neither of which has a standard British counterpart." }, { "market": "CA", "term": "eave", "alsoCalled": [ "eavestrough", "overhang", "drip edge" ], "exactness": "false-friend", "note": "EAVESTROUGH is the Canadian word for the GUTTER itself, so a reference to eavestrough is a reference to the rainwater goods rather than to the roof edge." } ], "standards": [ { "market": "UK", "standard": "BS 5534 / BS 5250", "covers": "Slating and tiling including eaves detailing and fixing, and the management of moisture in buildings including roof ventilation at eaves." }, { "market": "US", "standard": "IRC R905.1.2 / ASTM D1970", "covers": "Ice barriers required from the eaves edge to a point inside the exterior wall line, and self-adhering polymer-modified sheet." } ], "calculators": [ { "slug": "attic-baffle-vent-calculator", "json": "https://craftquantities.com/api/v1/calculators/attic-baffle-vent-calculator.json" }, { "slug": "roofing-underlayment-calculator", "json": "https://craftquantities.com/api/v1/calculators/roofing-underlayment-calculator.json" }, { "slug": "fascia-board-calculator", "json": "https://craftquantities.com/api/v1/calculators/fascia-board-calculator.json" } ], "confusions": [ { "question": "Why does the eaves course of tiles need counting separately?", "answer": "Because it is not laid like the rest of the roof. At the eaves the covering has to start with a doubled or a shortened course so that the first visible course has something beneath it and the edge is not a single thickness — with plain tiles that means an under-eaves course of short tiles, and with slates a shorter starter course. So the roof has more units than a straight area division suggests, and they are not all the same unit: the eaves tiles or starter slates are a separate item, ordered separately, and a take-off that multiplies area by units per square metre will be short by a whole course along every eaves. The same applies at the ridge and the verge, which is why a tiling schedule lists the perimeter details as line items rather than folding them into the area." }, { "question": "What is the eaves doing for the roof's ventilation?", "answer": "On a cold roof it is the inlet, and it is the half of the system most often blocked. A cold roof depends on air entering low at the eaves, passing over the insulation, and leaving high at the ridge — which requires a continuous free path above the insulation at the eaves, commonly expressed as an equivalent continuous gap in millimetres along the whole run. The failure is routine: insulation is pushed hard into the eaves during an upgrade, sealing the inlet completely, and the roof that was dry for decades starts condensing the following winter. That is what an eaves baffle or a proprietary eaves tray exists for — to hold the insulation back and preserve the path — and it is the first thing to look for in a loft that has become damp after being insulated." }, { "question": "What does an overhang actually buy?", "answer": "Three things, and they are worth separating because only one of them is about rain. First, it throws water clear of the wall, which keeps the wall dry and keeps the wall's own details — the render, the pointing, the window heads — out of the worst of the weather; a house with no overhang puts all of that in the rain. Second, it shades: an overhang blocks high summer sun while admitting low winter sun, which in a warm climate is a deliberate design dimension rather than a by-product, and is why Australian eaves are sized against the latitude. Third, it protects the junction between roof and wall, which is the hardest part of the envelope to detail and the most expensive to put right. A flush eaves is a legitimate architectural choice that spends all three." } ], "related": [ "verge", "ridge", "ice-dam" ] }, { "slug": "valley", "concept": "Roof valley", "family": "envelope", "definition": "The internal angle where two roof slopes meet, collecting the water from both and carrying it down to the eaves. The most concentrated water path on a pitched roof and the most common place for one to leak.", "url": "https://craftquantities.com/glossary/valley/", "names": [ { "market": "UK", "term": "valley", "alsoCalled": [ "open valley", "swept valley", "laced valley", "valley gutter", "valley trough" ], "exactness": "close", "note": "A SWEPT valley curves whole tiles round the angle; a LACED valley interleaves them over a wider tile. Both are craft details in plain tile with no equivalent in a profiled or sheet covering." }, { "market": "AU", "term": "valley", "alsoCalled": [ "valley gutter", "valley tray", "valley iron" ], "exactness": "close", "note": "Almost always a metal valley tray beneath the covering, since the dominant coverings are profiled tile and sheet and neither can be swept." }, { "market": "US", "term": "valley", "alsoCalled": [ "open valley", "closed-cut valley", "woven valley", "California valley" ], "exactness": "false-friend", "note": "A WOVEN valley interlaces shingles from both slopes across the angle with no metal at all, which is only possible because an asphalt shingle bends. No British tiled roof can be woven." }, { "market": "CA", "term": "valley", "alsoCalled": [ "open valley", "closed valley", "valley flashing" ], "exactness": "close", "note": "As the United States, with open metal valleys preferred in snow country because a woven or closed valley holds ice." } ], "standards": [ { "market": "UK", "standard": "BS 5534 / BS EN 12588", "covers": "Slating and tiling including valley construction, and rolled lead sheet for valley linings with maximum piece lengths." }, { "market": "US", "standard": "IRC R905.2.8.2 / ASTM D1970", "covers": "Valley lining requirements by roof covering type, and self-adhering membrane beneath valleys." } ], "calculators": [ { "slug": "hip-valley-rafter-cutlist-calculator", "json": "https://craftquantities.com/api/v1/calculators/hip-valley-rafter-cutlist-calculator.json" }, { "slug": "roofing-underlayment-calculator", "json": "https://craftquantities.com/api/v1/calculators/roofing-underlayment-calculator.json" }, { "slug": "roof-covering-fixing-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-covering-fixing-calculator.json" } ], "confusions": [ { "question": "Why do valleys leak more than the rest of the roof?", "answer": "Because they carry the water off two slopes through one narrow channel, so the volume per metre of detail is far higher than anywhere else on the roof — and because every unit along a valley is a CUT unit. A cut tile or slate is smaller, has lost the part of itself that was nailed, and often ends up held by adhesive or by a single fixing at an awkward angle. Add that the valley is where debris collects, that it is the last place to dry, and that in cold climates it is where ice forms first, and the concentration of risk is obvious. The practical consequence is that valley detail is specified rather than left to the roofer, and that a leak reported somewhere in the middle of a roof very often traces back to a valley above it." }, { "question": "What is a swept valley, and why can it not be done in every tile?", "answer": "It is a valley formed entirely in the covering, with no lining at all: the courses are carried round the angle in a curve using tapered tile-and-a-halves and purpose-made valley tiles, so the roof appears continuous through the intersection. It is possible only with a small flat unit — plain tiles or slates — because the curve is made by rotating many small pieces slightly, and a large profiled tile cannot rotate without breaking the interlock. It is expensive, it is slow, and on the right building it is the only detail that looks correct, which is why it survives on historic and high-quality work. A LACED valley is the related detail using a wider tile bridging the angle. Neither is available on an interlocking concrete tile roof, where the answer is a lined open valley." }, { "question": "How wide does an open valley have to be?", "answer": "Wide enough for the water and the debris, and the second one governs more often than the first. Guidance gives a minimum exposed width for the lining — typically well over a hundred millimetres of clear channel between the cut edges of the covering — and it widens as the roof area draining into it grows and as the pitch falls, because a shallower valley moves water more slowly and backs up further. But the real-world sizing question is blockage: a valley narrow enough to be bridged by a lodged leaf pile or a tennis ball will surcharge under the tiles either side of it, and the resulting leak is nowhere near the valley. That is the argument for the wider channel and for clearing valleys as maintenance rather than waiting for a symptom." } ], "related": [ "verge" ] }, { "slug": "dry-lining", "concept": "Dry lining and drywall installation", "family": "finishes", "definition": "Finishing an internal wall or ceiling with gypsum board rather than with wet plaster. What varies is what the board is fixed TO — a timber or metal frame, or the masonry itself via adhesive dabs.", "url": "https://craftquantities.com/glossary/dry-lining/", "names": [ { "market": "UK", "term": "dry lining", "alsoCalled": [ "dot and dab", "dab and stab", "drylining", "tape and joint" ], "exactness": "false-friend", "note": "DOT AND DAB fixes board straight onto masonry with adhesive, leaving a void behind it. The board is then usually skimmed with a thin plaster coat rather than taped and jointed, which is the opposite of American practice." }, { "market": "AU", "term": "plasterboard lining", "alsoCalled": [ "gyprock", "dry lining", "stud lining", "adhesive daubs" ], "exactness": "close", "note": "Gyprock is a brand used generically. Adhesive daubs onto masonry are used, usually combined with mechanical fixings rather than instead of them." }, { "market": "US", "term": "drywall", "alsoCalled": [ "hanging drywall", "sheetrock", "taping and finishing", "gypsum board" ], "exactness": "false-friend", "note": "Drywall is both the material and the operation. It is screwed to framing; there is no dot-and-dab equivalent, and the finish is taped and jointed to a level rather than skimmed." }, { "market": "CA", "term": "drywall", "alsoCalled": [ "gypsum board", "taping", "boarding" ], "exactness": "close", "note": "As the United States, with taping a distinct trade named separately from hanging." } ], "standards": [ { "market": "UK", "standard": "BS 8212 / BS EN 520", "covers": "Code of practice for dry lining and partitioning using gypsum plasterboard, and the board specification itself." }, { "market": "US", "standard": "ASTM C840 / GA-214", "covers": "Application and finishing of gypsum board, and the levels of gypsum board finish from Level 0 to Level 5." } ], "calculators": [ { "slug": "drywall-lamination-adhesive-calculator", "json": "https://craftquantities.com/api/v1/calculators/drywall-lamination-adhesive-calculator.json" }, { "slug": "drywall-stud-adhesive-calculator", "json": "https://craftquantities.com/api/v1/calculators/drywall-stud-adhesive-calculator.json" }, { "slug": "ceiling-plasterboard-sheet-calculator", "json": "https://craftquantities.com/api/v1/calculators/ceiling-plasterboard-sheet-calculator.json" } ], "confusions": [ { "question": "What is dot and dab, and why does it matter for fixing things to the wall?", "answer": "It is board stuck to masonry on blobs of adhesive rather than screwed to a frame, and it leaves a void of perhaps ten to twenty millimetres between the board and the wall. That void is the reason ordinary plasterboard fixings fail on it: a plug expanding behind the board has nothing to expand into, and a hollow-wall anchor designed for a stud partition assumes a void of a particular depth with nothing behind it. Hanging anything of weight on a dot-and-dab wall means either finding a dab, which is guesswork, or using a long fixing that passes through the board and the void and anchors into the masonry beyond. That is also why a dot-and-dab wall sounds hollow when tapped and a visitor concludes it is a stud wall, which changes everything they would plan to do to it." }, { "question": "Skim or tape and joint — what is the difference in the finish?", "answer": "Two completely different ways of arriving at a paintable wall. British practice usually SKIMS: a thin coat of finish plaster applied over the whole board, giving a continuous seamless surface with no distinction between the board and the joint, which is why British walls are usually painted without any board texture showing. American practice TAPES AND JOINTS: only the joints and the fastener heads are covered, feathered out with compound and sanded, leaving the board's own paper face as the finish across most of the wall. Each has its logic — skimming is faster to a high finish over small areas, taping is far less material over large ones — and each produces a different substrate. Paint behaves differently on the two, and so does any repair." }, { "question": "What do the Levels of finish mean, and is there a British equivalent?", "answer": "The American system grades how far the taping and finishing has been taken, from Level 0 — board hung, nothing done — through Level 3 for a wall receiving a heavy texture, Level 4 as the normal painted finish, to Level 5, a skim coat over the entire surface for critical lighting or gloss paint. It is a contractual specification: the level is stated, priced and inspected. British practice has no directly equivalent ladder, because skimming produces something close to Level 5 as standard, and the specification tends to describe the plaster system rather than a grade of finish. When reading across markets that is worth knowing in both directions: an American Level 4 wall under a raking light will show joints a British client would consider a defect, and specifying a British skim to an American contractor is asking for their most expensive option." } ], "related": [ "plasterboard", "suspended-ceiling" ] }, { "slug": "rising-main", "concept": "Rising main and water service", "family": "services", "definition": "The pipe bringing cold water from the supply into and up through a building. What differs across markets is where the boundary of responsibility sits along it, and whether anything downstream is stored.", "url": "https://craftquantities.com/glossary/rising-main/", "names": [ { "market": "UK", "term": "rising main", "alsoCalled": [ "mains cold", "incoming main", "service pipe", "communication pipe" ], "exactness": "false-friend", "note": "SERVICE PIPE and COMMUNICATION PIPE are not synonyms: the communication pipe is the utility's up to the boundary stop tap, the service pipe is the owner's from there in. The split decides who pays for a leak." }, { "market": "AU", "term": "water service", "alsoCalled": [ "service pipe", "mains", "riser" ], "exactness": "close", "note": "Water service is the standard term, with the meter and the property boundary marking the same split of responsibility." }, { "market": "US", "term": "water service line", "alsoCalled": [ "service line", "main", "supply line", "riser" ], "exactness": "false-friend", "note": "MAIN in American usage normally means the street main in the road, so telling an American plumber the leak is on the main sends them outside the property." }, { "market": "CA", "term": "water service", "alsoCalled": [ "service line", "curb stop", "main shutoff" ], "exactness": "close", "note": "As the United States, with the curb stop naming the boundary valve that British usage calls the outside stop tap." } ], "standards": [ { "market": "UK", "standard": "Water Supply (Water Fittings) Regulations / BS EN 806", "covers": "Requirements for water fittings, backflow protection and the installation of drinking water systems inside buildings." }, { "market": "US", "standard": "IPC Chapter 6 / AWWA C800", "covers": "Water supply and distribution sizing, and underground service line fittings." } ], "calculators": [ { "slug": "domestic-water-pipe-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/domestic-water-pipe-sizing-calculator.json" }, { "slug": "pipe-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/pipe-volume-calculator.json" }, { "slug": "water-heater-recovery-time-calculator", "json": "https://craftquantities.com/api/v1/calculators/water-heater-recovery-time-calculator.json" } ], "confusions": [ { "question": "Where does the utility's pipe stop and the owner's begin?", "answer": "At the boundary, and the words either side of that point are different. In British usage the COMMUNICATION pipe runs from the water main in the street to the boundary stop tap, and it belongs to the water company; the SERVICE pipe runs from there to the property and belongs to the owner. So a leak in the road is the company's and a leak under the front garden is usually the owner's, which is why the outside stop tap is worth finding before it is needed rather than after. American usage puts the same boundary at the curb stop, and Canadian at the same place with the same name. The practical point for anyone reading a report across markets: main means the street in America and the incoming pipe in Britain, and the difference is whose bill it is." }, { "question": "Why does a single kitchen tap have to be fed directly from it?", "answer": "Because it is the drinking water point, and older British systems stored cold water in a loft cistern. A traditional indirect system fed the bathroom, the WC and the hot water cylinder from an open tank in the roof — water that sat in an accessible vessel, warmed in summer, and was open to whatever entered the loft. The kitchen tap was therefore taken straight off the rising main before any of that, so there was one outlet of water fit to drink. That convention survives in the regulations and in the plumbing habits of the country long after most houses became directly fed by a combi. Anybody working on an older system needs to know it, because reconnecting a kitchen tap to a stored supply is a regulatory breach and not merely a preference." }, { "question": "What size should it be, and why is the answer usually flow rather than pressure?", "answer": "Sized on the flow the property needs and the pressure available to deliver it, and the constraint is almost always a long run of undersized pipe rather than the pressure at the main. Pressure at the street is generally adequate; what it has to survive is the resistance of everything between there and the tap, and that resistance rises steeply as diameter falls — halving the bore multiplies the loss many times over for the same flow. So a house with poor flow at the top floor very often has a modern boiler, an adequate street pressure, and a fifty-year-old service pipe of small diameter running thirty metres from the road. Replacing the last few metres inside the house changes nothing; the run is the problem, and measuring the flow rate at the outside stop tap is what separates the two." } ], "related": [ "stopcock" ] }, { "slug": "frog", "concept": "Frog and perforations in a brick", "family": "materials", "definition": "The recess pressed into one or both bed faces of a brick, or the holes through it. Both reduce the clay used and the weight, and both change how much mortar the wall takes and how strong the bed joint is.", "url": "https://craftquantities.com/glossary/frog/", "names": [ { "market": "UK", "term": "frog", "alsoCalled": [ "frogged brick", "single frog", "perforated brick", "keyed brick" ], "exactness": "identical", "note": null }, { "market": "AU", "term": "frog", "alsoCalled": [ "frogged brick", "cored brick", "perforated brick" ], "exactness": "identical", "note": null }, { "market": "US", "term": "frog", "alsoCalled": [ "cored brick", "core holes", "panel" ], "exactness": "close", "note": "Frog is understood but American brick is far more often CORED — holes right through — than frogged, so the up-or-down question rarely arises and the coring is a fixed feature rather than a choice at laying." }, { "market": "CA", "term": "frog", "alsoCalled": [ "cored brick", "core holes" ], "exactness": "close", "note": "As the United States: cored brick dominates, so the frog-up question that governs a British bed joint effectively never arises on site." } ], "standards": [ { "market": "UK", "standard": "BS EN 771-1", "covers": "Specification for masonry units: clay units, including the classification of perforations and the void percentage limits." }, { "market": "US", "standard": "ASTM C216 / ASTM C652", "covers": "Facing brick and hollow brick, with the core area limits that separate solid from hollow units." } ], "calculators": [ { "slug": "brick-calculator", "json": "https://craftquantities.com/api/v1/calculators/brick-calculator.json" }, { "slug": "masonry-pier-axial-capacity-calculator", "json": "https://craftquantities.com/api/v1/calculators/masonry-pier-axial-capacity-calculator.json" }, { "slug": "cmu-wall-self-weight-calculator", "json": "https://craftquantities.com/api/v1/calculators/cmu-wall-self-weight-calculator.json" } ], "confusions": [ { "question": "Frog up or frog down — is there a right answer?", "answer": "Up, for anything structural, and the reason is the bed joint. Laid frog UP, the recess fills with mortar as the next brick is bedded, so the joint is solid through its whole depth and the two bricks are keyed to each other. Laid frog DOWN, the recess is a void unless the bricklayer deliberately fills it — and most do not, because it is slower and uses noticeably more mortar — so the bed joint is reduced to the ring of mortar around the edge of the frog. That reduces the bearing area, reduces compressive strength, and leaves a cavity in the wall that can hold water and transmit sound. Frog down is faster and uses less material, which is exactly why it happens, and on a garden wall it matters much less than on a pier carrying a beam." }, { "question": "How much does a frog or a core change the mortar quantity?", "answer": "Enough that a takeoff based on joint dimensions alone will be short. A conventional estimate multiplies bed and perpend joint volume by the number of joints, and that assumes a flat bed face. A single-frogged brick laid frog up adds the frog's volume to every bed joint, which on a common frog is a meaningful fraction of the brick — enough to push a job's mortar requirement up by a noticeable percentage over a large wall. Cored brick behaves differently again: the cores are not usually filled in a veneer, so they add nothing to mortar, but they do change the unit's weight and its thermal mass. The practical rule is that the brick's geometry is an input to the mortar quantity and not a detail, and that an order calculated for a solid brick will run out on a frogged one." }, { "question": "Does a frogged brick differ from a perforated one structurally?", "answer": "Yes, and the standards separate them by how much of the unit is void. A FROG is a recess in the bed face that does not go through, so the brick has a continuous solid section from face to face and behaves substantially like a solid unit once the frog is filled. PERFORATIONS go right through, so the unit's net section is reduced permanently and it is classified by the percentage of void — which decides whether it counts as a solid, a perforated or a hollow unit, and that classification governs its strength, its fire performance and whether it may be used where a solid unit is specified. The difference shows up in practice when drilling: a perforated brick offers a fixing far less material to hold, which is why a heavy fixing into one needs a resin anchor rather than a plug." } ], "related": [ "brick-bond" ] }, { "slug": "stair-going", "concept": "Stair rise and going", "family": "measurement", "definition": "The two dimensions that define a step: how far it lifts, and how far it advances. Every stair rule in every market is a relationship between those two, and the markets name the second one differently.", "url": "https://craftquantities.com/glossary/stair-going/", "names": [ { "market": "UK", "term": "rise and going", "alsoCalled": [ "riser", "tread", "total going", "pitch line" ], "exactness": "false-friend", "note": "GOING is the horizontal distance one step advances, measured nosing to nosing; TOTAL GOING is the whole flight. A TREAD is the board you stand on, which is wider than the going by the nosing overlap." }, { "market": "AU", "term": "rise and going", "alsoCalled": [ "riser", "tread", "going", "slope relationship" ], "exactness": "close", "note": "British terms under Australian standards, with the rise-and-going relationship expressed as a slope range rather than a single formula." }, { "market": "US", "term": "rise and run", "alsoCalled": [ "riser", "tread depth", "total run", "unit run" ], "exactness": "false-friend", "note": "RUN means the horizontal advance of one step, but TOTAL RUN means the whole flight and plain run is used for both — so a run figure has to be qualified before it can be used." }, { "market": "CA", "term": "rise and run", "alsoCalled": [ "riser", "tread run", "total run" ], "exactness": "false-friend", "note": "As the United States, with the same ambiguity between unit run and total run." } ], "standards": [ { "market": "UK", "standard": "Approved Document K / BS 5395-1", "covers": "Protection from falling, collision and impact, including rise and going limits by stair category, and stairs, ladders and walkways." }, { "market": "US", "standard": "IRC R311.7 / IBC 1011", "covers": "Stairway riser height and tread depth limits, the maximum variation between them, and nosing requirements." } ], "calculators": [ { "slug": "stair-calculator", "json": "https://craftquantities.com/api/v1/calculators/stair-calculator.json" }, { "slug": "stair-drop-cut-calculator", "json": "https://craftquantities.com/api/v1/calculators/stair-drop-cut-calculator.json" }, { "slug": "spiral-stair-headroom-calculator", "json": "https://craftquantities.com/api/v1/calculators/spiral-stair-headroom-calculator.json" } ], "confusions": [ { "question": "Is the going the same as the tread?", "answer": "No, and the difference is the nosing. The GOING is how far the stair advances per step, measured from the nosing of one tread to the nosing of the next — it is a distance along the stair. The TREAD is the physical board, and where there is a nosing it overhangs the riser below, so the board is wider than the going by that overhang. Order treads to the going and every board is short by the nosing; set out the stair to the tread width and the flight is longer than the space allows. The same trap exists in American usage between unit RUN and TREAD DEPTH, with the additional complication that some codes measure tread depth nosing to nosing anyway — so the word alone never settles it and the drawing has to show where the dimension is taken from." }, { "question": "Why is there a rule relating rise to going rather than limits on each?", "answer": "Because comfort and safety depend on the relationship, not on either dimension alone. A person climbing a stair takes a stride whose length is roughly fixed, and a step that lifts a long way must advance less if the stride is to stay natural — so a tall rise with a deep going is exhausting and a shallow rise with a short going is a trip hazard. Every market encodes that in some form: British guidance gives both individual limits and a combined rule around twice the rise plus the going, and American codes set a maximum riser and a minimum tread which together imply a similar band. The practical consequence is that you cannot fix a stair that is too steep by adjusting only one dimension; both move together, and the total run of the flight moves with them." }, { "question": "Why does the CONSISTENCY matter as much as the dimension?", "answer": "Because people climb stairs without looking at them. After the first two or three steps the body has learned the rhythm and stops watching, so a single step that differs from its neighbours is the one that causes a fall — and the falls it causes are on the way DOWN, with momentum. That is why every code limits the variation between the largest and smallest riser in a flight far more tightly than it limits the riser itself, commonly to a few millimetres across the whole stair. It is also the reason the bottom and top steps are the usual offenders: a floor finish added after the stair was set out changes one riser and nothing else, and a stair that was compliant becomes the most dangerous kind of stair, which is one that looks regular and is not." } ], "related": [ "nominal-size", "baluster" ] }, { "slug": "pointing", "concept": "Pointing and joint profile", "family": "materials", "definition": "The finished surface of a mortar joint — how it is shaped, compacted and set back relative to the face of the masonry. Decides how well the joint sheds water and how the wall reads.", "url": "https://craftquantities.com/glossary/pointing/", "names": [ { "market": "UK", "term": "pointing", "alsoCalled": [ "bucket handle", "weather struck", "flush", "recessed", "tuck pointing" ], "exactness": "false-friend", "note": "TUCK POINTING in British usage is a decorative technique: a coloured mortar matching the brick with a fine white ribbon tucked into it to imitate very fine joints. It is not repointing." }, { "market": "AU", "term": "pointing", "alsoCalled": [ "ironed joint", "raked joint", "weather struck", "flush" ], "exactness": "close", "note": "British profile names with ironed used where British usage says bucket handle, after the jointing iron that forms it." }, { "market": "US", "term": "tooled joint", "alsoCalled": [ "concave joint", "V joint", "raked joint", "tuckpointing", "repointing" ], "exactness": "false-friend", "note": "TUCKPOINTING in American usage means REPOINTING — cutting out and replacing failed mortar. That is the opposite of the British decorative sense and is the commonest cross-market misunderstanding here." }, { "market": "CA", "term": "tooled joint", "alsoCalled": [ "concave joint", "repointing", "tuckpointing" ], "exactness": "false-friend", "note": "As the United States, with the same use of tuckpointing for repair work." } ], "standards": [ { "market": "UK", "standard": "BS EN 1996-2 / PD 6697", "covers": "Design considerations, selection of materials and execution of masonry, including joint finishing and exposure." }, { "market": "US", "standard": "TMS 602 / ASTM C1713", "covers": "Specification for masonry structures including tooling of joints, and mortars for repointing historic masonry." } ], "calculators": [ { "slug": "tuckpointing-repair-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/tuckpointing-repair-volume-calculator.json" }, { "slug": "brick-calculator", "json": "https://craftquantities.com/api/v1/calculators/brick-calculator.json" }, { "slug": "masonry-control-joint-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/masonry-control-joint-spacing-calculator.json" } ], "confusions": [ { "question": "Does tuckpointing mean repair or decoration?", "answer": "Both, depending on which side of the Atlantic the specification was written on, and they are not related operations. In AMERICAN usage tuckpointing means repointing: raking out failed mortar and replacing it, which is repair work priced by the square metre of wall and the depth cut out. In BRITISH usage tuck pointing is a decorative finish from the eighteenth and nineteenth centuries — the joint is filled with a mortar coloured to match the brick, and a fine ribbon of white lime putty is then tucked into a groove cut in it, so that the wall appears to be built with far finer joints than it is. It is highly skilled, it is slow, and it appears on buildings where the imitation of gauged brickwork was the point. Quoting one against the other is an order-of-magnitude pricing error in either direction." }, { "question": "Which profile sheds water best, and does it matter?", "answer": "It matters a great deal on an exposed wall and hardly at all on a sheltered one, which is why the choice is usually made on appearance and then regretted on one elevation. A WEATHER STRUCK joint is cut back at the top and left proud at the bottom, so water runs off the sloping face and away — it is the most weather-resistant traditional profile and it is why it dominates on exposed British elevations. A BUCKET HANDLE or concave joint is compacted with a rounded tool, which densifies the mortar surface and sheds reasonably while being far faster to form. A RECESSED or raked joint is the worst: it creates a ledge on every course that holds water and, in a freeze, ice. It also reduces the joint's cover over the masonry. It looks excellent, and on a wall that gets weather it is a maintenance decision." }, { "question": "Why does raking out too deep, or not deep enough, both fail?", "answer": "Because new pointing has to have enough depth to grip and enough sound mortar behind it to grip onto. Rake out too SHALLOW — a common shortcut, cutting perhaps five millimetres — and the new mortar is a thin skin with very little mechanical key, which falls out in sheets within a few years and takes the face of the brick with it if it was too strong a mix. Rake out too DEEP, or with an angle grinder that widens the joint and scores the brick above and below, and you have removed sound material, enlarged the joint so the wall reads wrong, and cut the arrises off the bricks permanently. Guidance generally puts the depth at around twice the joint thickness, cut square and by hand on anything old, and the grinder is the tool that has destroyed more historic brickwork than weather has." } ], "related": [ "mortar-designation" ] }, { "slug": "lime", "concept": "Lime binders", "family": "materials", "definition": "A binder made by burning limestone. It divides into non-hydraulic lime, which sets by absorbing carbon dioxide from the air, and hydraulic lime, which sets by reacting with water like a weak cement — two different materials under one word.", "url": "https://craftquantities.com/glossary/lime/", "names": [ { "market": "UK", "term": "lime", "alsoCalled": [ "lime putty", "NHL", "hydraulic lime", "hot lime", "lime mortar" ], "exactness": "false-friend", "note": "NHL 2, 3.5 and 5 are hydraulic and set under water; lime PUTTY is non-hydraulic and sets by carbonation over months. The word alone does not say which, and they are not substitutes." }, { "market": "AU", "term": "lime", "alsoCalled": [ "builders lime", "hydrated lime", "lime putty" ], "exactness": "close", "note": "Builders lime normally means bagged hydrated non-hydraulic lime used as a plasticiser in cement mortar, rather than as a binder in its own right." }, { "market": "US", "term": "lime", "alsoCalled": [ "hydrated lime", "Type S lime", "Type N lime", "NHL" ], "exactness": "false-friend", "note": "TYPE S and TYPE N here classify hydrated lime by its hydration, and collide directly with mortar Types S and N, which are strength designations for the finished mortar. Same letters, different property." }, { "market": "CA", "term": "lime", "alsoCalled": [ "hydrated lime", "Type S lime", "mason's lime" ], "exactness": "false-friend", "note": "As the United States, with the same Type S collision between lime classification and mortar strength designation." } ], "standards": [ { "market": "UK", "standard": "BS EN 459-1", "covers": "Building lime: definitions, specification and conformity criteria, including the NHL 2, 3.5 and 5 classification." }, { "market": "US", "standard": "ASTM C207 / ASTM C1489", "covers": "Hydrated lime for masonry purposes including Types N and S, and lime putty for structural purposes." } ], "calculators": [ { "slug": "lime-stabilization-calculator", "json": "https://craftquantities.com/api/v1/calculators/lime-stabilization-calculator.json" }, { "slug": "thinset-mortar-calculator", "json": "https://craftquantities.com/api/v1/calculators/thinset-mortar-calculator.json" }, { "slug": "stone-veneer-mortar-calculator", "json": "https://craftquantities.com/api/v1/calculators/stone-veneer-mortar-calculator.json" } ], "confusions": [ { "question": "What is the difference between hydraulic and non-hydraulic lime?", "answer": "How it sets, and it changes everything about how the work is programmed. NON-HYDRAULIC lime — lime putty, sometimes called fat or air lime — sets by absorbing carbon dioxide from the air, a process that starts at the surface and works inward over months and years. It cannot set under water, it cannot set in a sealed void, and it must be protected from frost and from drying too fast for a long time after it is applied. HYDRAULIC lime contains clay impurities that give it cementitious compounds, so it sets by reacting with water like a weak cement, in days rather than months, and will set under water. NHL 2 is the weakest and most permeable, NHL 5 the strongest and closest to cement. Specifying NHL 5 where NHL 2 belongs is the same category of error as specifying cement on a soft wall, just less extreme." }, { "question": "Why does an old building need lime rather than cement?", "answer": "Because of what the wall does with water, and because of what happens at the joint. A solid wall built with soft brick or stone and lime mortar handles rain by absorbing it and then releasing it, and the JOINTS are the main route out — lime is more permeable than the units, so the wall breathes through the mortar and the units stay relatively dry. Cement pointing reverses that: it is less permeable than the units, so the water leaves through the brick or stone face instead, carrying salts with it and freezing in it. The face then spalls. The second reason is movement: an old wall flexes, and lime accommodates that by microcracking and partly re-healing, where cement cracks once and stays cracked, usually taking the unit with it. Both effects take years, which is why the damage from a cement repair is normally attributed to something else." }, { "question": "What does Type S mean — is it the lime or the mortar?", "answer": "Both, and they are unrelated properties, which is a genuine hazard in American specifications. ASTM C207 classifies hydrated LIME as Type N or Type S, where S means special hydrate with tighter limits on unhydrated oxides and on plasticity — it is about how the lime behaves in the mix. ASTM C270 classifies MORTAR as Types M, S, N, O and K in descending order of compressive strength, and Type S mortar is a strength designation containing cement, lime and sand. So a specification saying Type S might be naming the lime or naming the mortar, and the two have no connection: Type S lime appears in Type N mortar routinely. The only safe reading is to check which standard is cited, and a specification that cites neither has not specified anything." } ], "related": [ "cement" ] }, { "slug": "baluster", "concept": "Balusters, spindles and stair parts", "family": "finishes", "definition": "The components of a stair or balcony barrier: the verticals filling the gap, the rail they support, the posts at each end, and the board carrying the treads.", "url": "https://craftquantities.com/glossary/baluster/", "names": [ { "market": "UK", "term": "spindle", "alsoCalled": [ "baluster", "newel", "handrail", "string", "balustrade" ], "exactness": "false-friend", "note": "A STRING is the raking board into which the treads are housed. BALUSTRADE is the whole assembly, and a SPINDLE and a BALUSTER are the same component with the first used more in domestic joinery." }, { "market": "AU", "term": "baluster", "alsoCalled": [ "spindle", "newel post", "stringer", "balustrade" ], "exactness": "close", "note": "Stringer used where British usage says string, with balustrade for the assembly as in the UK." }, { "market": "US", "term": "baluster", "alsoCalled": [ "spindle", "newel post", "stringer", "guard", "railing" ], "exactness": "false-friend", "note": "GUARD is the code term for the whole barrier and is what a code clause will say; STRINGER is the raking board. Railing covers both the handrail and the whole assembly depending on context." }, { "market": "CA", "term": "baluster", "alsoCalled": [ "spindle", "guard", "stringer", "picket" ], "exactness": "false-friend", "note": "As the United States, and STRINGER collides with Canadian strapping usage, where stringers can also mean light battens run across framing." } ], "standards": [ { "market": "UK", "standard": "Approved Document K / BS 6180", "covers": "Protection from falling, including guarding heights and the 100 mm sphere rule, and barriers in and about buildings." }, { "market": "US", "standard": "IRC R312 / IBC 1015", "covers": "Guards: required height, the 4-inch sphere limitation, and the loads a guard must resist." } ], "calculators": [ { "slug": "baluster-calculator", "json": "https://craftquantities.com/api/v1/calculators/baluster-calculator.json" }, { "slug": "stair-calculator", "json": "https://craftquantities.com/api/v1/calculators/stair-calculator.json" }, { "slug": "steel-stair-stringer-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/steel-stair-stringer-length-calculator.json" } ], "confusions": [ { "question": "Why is the spacing rule expressed as a sphere rather than a gap?", "answer": "Because the hazard is a child's body passing through, and a child is not a flat gauge. Both markets express the limit the same way — a sphere of 100 mm in British guidance, 4 inches in American — and the sphere must not be able to pass through any opening in the guarding. Stating it as a sphere rather than a dimension catches the openings a simple width measurement misses: a triangular gap at the bottom of a flight where the tread, the riser and the bottom rail meet; a diagonal opening in a chevron pattern; the gap beside a newel where the rake changes. It is also why the rule is checked at the worst point rather than at the typical spacing, and why a balustrade that measures correctly between spindles can still fail where the geometry changes." }, { "question": "How many spindles does a flight actually take?", "answer": "More than the run divided by the spacing, and the arithmetic has two traps. The first is the same plus-one that catches every spacing calculation: a run with n gaps has n+1 verticals, and forgetting it leaves the flight one short at the top. The second is the rake. On a raking flight the spindles stand vertical while the rail climbs, so the horizontal spacing between them must be measured along the horizontal, not along the rail — spacing set out along the raking rail produces horizontal gaps larger than intended and can fail the sphere test even though the rail spacing looks right. On a stair with two spindles per tread the count comes from the tread number instead, which is why most joinery schedules give spindles per tread rather than a spacing." }, { "question": "What is the string, and why does its type change the whole stair?", "answer": "It is the raking board each side that carries the treads, and there are two kinds that look different and are built completely differently. A CLOSED or housed string runs as a continuous board with the treads and risers housed into trenches cut in its inner face, wedged and glued — so the ends of the treads are hidden and the stair reads as a solid diagonal. A CUT or open string is cut to the profile of the steps, so the tread ends are exposed and finished with a return nosing, and the balusters sit on the treads rather than on the string. The second is more work, more visible, and is the traditional arrangement on a stair meant to be seen. Which one is being priced changes the joinery substantially, and a drawing that only shows a rake has not said." } ], "related": [ "stair-going", "guardrail" ] }, { "slug": "fused-spur", "concept": "Fused connection unit", "family": "services", "definition": "A fixed wiring accessory containing a cartridge fuse, connecting an appliance permanently to a circuit at a lower protection level than the circuit itself carries.", "url": "https://craftquantities.com/glossary/fused-spur/", "names": [ { "market": "UK", "term": "fused spur", "alsoCalled": [ "FCU", "fused connection unit", "switched spur", "flex outlet" ], "exactness": "absent", "note": "Exists because a ring final circuit is protected at 32 A while an appliance flex is not. A SPUR strictly means a branch off a ring; the fuse and the spur are separate ideas commonly named together." }, { "market": "AU", "term": "fused connection unit", "alsoCalled": [ "appliance outlet", "switched fused outlet" ], "exactness": "absent", "note": "Radial circuits at lower protection levels mean the component is uncommon; a fixed appliance is normally supplied from its own appropriately rated circuit instead." }, { "market": "US", "term": "(no direct equivalent)", "alsoCalled": [ "junction box", "appliance disconnect", "hard-wired connection" ], "exactness": "absent", "note": "A branch circuit is protected at 15 or 20 A, which the appliance cord survives, so no intermediate fuse is required. Where local protection is needed the appliance carries it internally." }, { "market": "CA", "term": "(no direct equivalent)", "alsoCalled": [ "junction box", "disconnect means" ], "exactness": "absent", "note": "As the United States, with a local disconnect required for some fixed appliances — which is about isolation for maintenance rather than about protecting a flex." } ], "standards": [ { "market": "UK", "standard": "BS 1363-4 / BS 7671", "covers": "Fused connection units as part of the 13 A plug and socket system, and the wiring regulations governing spurs off a final circuit." }, { "market": "US", "standard": "NFPA 70 (NEC) Article 422", "covers": "Appliances: branch circuit sizing, disconnecting means, and the conditions for permanent connection." } ], "calculators": [ { "slug": "breaker-size-calculator", "json": "https://craftquantities.com/api/v1/calculators/breaker-size-calculator.json" }, { "slug": "outlets-per-circuit-calculator", "json": "https://craftquantities.com/api/v1/calculators/outlets-per-circuit-calculator.json" }, { "slug": "wire-gauge-voltage-drop-calculator", "json": "https://craftquantities.com/api/v1/calculators/wire-gauge-voltage-drop-calculator.json" } ], "confusions": [ { "question": "Why does Britain need a component nobody else does?", "answer": "Because the ring final circuit protects the cable in the wall at 32 A, which is far more than anything plugged into it can survive. On a portable appliance the plug carries the fuse and solves it. On a FIXED appliance — an extractor fan, a boiler, a towel rail, an outdoor light, a waste disposal — there is no plug, so without something in between the appliance's flex is connected directly to 32 A of available protection. The fused connection unit is that something: a fixed accessory with a cartridge fuse rated for the appliance, and usually a switch so the appliance can be isolated. An American branch circuit protected at 15 or 20 A does not create the gap, so the component never had to be invented." }, { "question": "What is a spur, and how many are allowed?", "answer": "A spur is a branch taken off a ring rather than part of the loop itself, and the rules exist because a spur is the one part of a ring not protected by having two paths. A single unfused spur may supply one single or one double socket, or one fixed appliance, and it is taken from a socket on the ring or from a junction box in it — the reasoning being that the spur cable carries only what that one point draws, not the whole ring's load. Anything beyond that goes through a FUSED spur, which drops the protection to the fuse rating and so allows a much smaller cable and more outlets beyond it. The common domestic error is extending a spur with a second socket, which puts two outlets on a cable protected at 32 A with no second path." }, { "question": "Switched or unswitched, and does the fuse rating matter?", "answer": "Both are choices with consequences. SWITCHED lets the appliance be isolated locally, which is what makes it safe to work on a boiler or a fan without going to the consumer unit, and it is why a switched unit is normal for anything that will ever need servicing. UNSWITCHED is used where nobody should casually turn the appliance off — a freezer, an alarm, a trickle-charging circuit — and the switch would be a hazard rather than a convenience. The FUSE rating is chosen for the appliance and its flex, not for convenience: 3 A for small loads, 13 A for heating loads, and fitting 13 A everywhere because it is what came in the box removes the protection the unit exists to provide." } ], "related": [ "ring-final-circuit" ] }, { "slug": "ridge", "concept": "Ridge, ridge board and ridge beam", "family": "envelope", "definition": "The horizontal line at the top of a pitched roof where two slopes meet, the timber the rafters meet at, and the units capping the junction. Three things under one word, and one of them is structural.", "url": "https://craftquantities.com/glossary/ridge/", "names": [ { "market": "UK", "term": "ridge", "alsoCalled": [ "ridge board", "ridge tile", "ridge beam", "dry ridge" ], "exactness": "false-friend", "note": "A ridge BOARD is a thin member the rafters land against; a ridge BEAM carries them. A ridge TILE is the covering. The word alone says which of the three only from context." }, { "market": "AU", "term": "ridge", "alsoCalled": [ "ridge capping", "ridge board", "ridge beam", "barge capping" ], "exactness": "close", "note": "Ridge capping is the standard term for the covering component, with the same board-against-beam structural distinction." }, { "market": "US", "term": "ridge", "alsoCalled": [ "ridge board", "ridge beam", "ridge cap", "ridge vent" ], "exactness": "close", "note": "The same three senses, and the ridge VENT is a distinct standard component forming the exhaust of the roof's ventilation path — far more consistently specified than in British practice." }, { "market": "CA", "term": "ridge", "alsoCalled": [ "ridge board", "ridge beam", "ridge cap", "ridge vent" ], "exactness": "close", "note": "As the United States, with the ventilation role of the ridge governed by a required intake-to-exhaust balance." } ], "standards": [ { "market": "UK", "standard": "BS 5534 / BS 8103-3", "covers": "Slating and tiling including ridge fixing and dry ridge systems, and structural design of low-rise buildings: timber floors and roofs." }, { "market": "US", "standard": "IRC R802.3 / R806", "covers": "Ridge board and ridge beam requirements including when a beam and bearing are required, and roof ventilation." } ], "calculators": [ { "slug": "roof-ridge-cap-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-ridge-cap-calculator.json" }, { "slug": "ridge-vent-linear-footage-calculator", "json": "https://craftquantities.com/api/v1/calculators/ridge-vent-linear-footage-calculator.json" }, { "slug": "ridge-beam-tributary-load-calculator", "json": "https://craftquantities.com/api/v1/calculators/ridge-beam-tributary-load-calculator.json" } ], "confusions": [ { "question": "What is the difference between a ridge board and a ridge beam?", "answer": "Whether it carries anything, and the answer decides what the walls below have to do. A ridge BOARD is a thin member — often no deeper than the rafter cut requires — that the opposing rafters bear against. It carries essentially no vertical load: the rafters push against each other across it, and the resulting outward thrust at their feet is taken by ceiling joists or collars acting as ties. A ridge BEAM carries the top of each rafter as a genuine support, so there is no opposing thrust and the rafters behave as simple spans — but the beam then has a real reaction at each end that must land on something able to take it, which usually means a post and a foundation. That is why removing a ceiling to make a vaulted space is a structural project: it removes the tie, which means the ridge board must become a ridge beam, which means new bearings." }, { "question": "Why is a mortar-bedded ridge now unusual?", "answer": "Because it fails predictably and the failure is above people's heads. Ridge tiles bedded in mortar rely on that mortar staying intact through decades of thermal movement, wind and frost at the most exposed line on the building — and it does not: the bed cracks, water gets behind it, the tiles loosen, and eventually one moves. British practice moved to DRY RIDGE systems, which fix each ridge unit mechanically to a batten with a ventilated profiled filler under it, and standards now effectively require mechanical fixing of ridge and hip units rather than relying on mortar alone. The secondary gain is ventilation: a dry ridge is a ready-made exhaust for the roof space, which a mortar bed sealed shut." }, { "question": "How is the ridge the exhaust of a roof's ventilation?", "answer": "Because warm air rises to the highest point, and a cold roof works by moving air from low to high. Air enters at the eaves, passes over the insulation picking up moisture, and has to leave at the top — so the ridge is where the exhaust belongs, and the ridge vent or the ventilated dry ridge provides it. The system only works BALANCED: exhaust without intake pulls air from inside the house through every ceiling penetration instead, which is worse than no ventilation, and intake without exhaust achieves nothing. That is why American codes state the intake and exhaust proportions explicitly and why the commonest British loft-damp finding — insulation blocking the eaves — disables a ridge vent that is working perfectly." } ], "related": [ "eaves", "shingle" ] }, { "slug": "threshold", "concept": "Threshold and door sill", "family": "finishes", "definition": "The assembly at the bottom of a doorway: the piece the door closes onto, the weathering at an external door, and the transition between two floor finishes.", "url": "https://craftquantities.com/glossary/threshold/", "names": [ { "market": "UK", "term": "threshold", "alsoCalled": [ "cill", "weather bar", "door bar", "transition strip", "level threshold" ], "exactness": "close", "note": "One word for the whole condition. A LEVEL threshold is a specific accessibility requirement with a maximum upstand, and is a different product from a weathered one." }, { "market": "AU", "term": "threshold", "alsoCalled": [ "door sill", "weather bar", "transition strip" ], "exactness": "close", "note": "As the UK, with sill used more freely for the external weathering component." }, { "market": "US", "term": "threshold", "alsoCalled": [ "saddle", "door sill", "transition strip", "sill pan" ], "exactness": "false-friend", "note": "SADDLE is the interior piece between two rooms; SILL is the exterior weathering component — and sill also means the sill plate on the foundation and the window sill, so it needs qualifying every time." }, { "market": "CA", "term": "threshold", "alsoCalled": [ "saddle", "sill", "sill pan", "transition" ], "exactness": "false-friend", "note": "As the United States, with the sill PAN — a preformed tray under an exterior door — a standard item that British practice details as a DPC tray instead." } ], "standards": [ { "market": "UK", "standard": "Approved Document M / Approved Document Q", "covers": "Access to and use of buildings including accessible thresholds, and security requirements for doorsets." }, { "market": "US", "standard": "IRC R311.3 / ADA 404.2.5", "covers": "Landings at required exterior doors and threshold height limits, and accessible threshold requirements." } ], "calculators": [ { "slug": "floor-transition-strip-calculator", "json": "https://craftquantities.com/api/v1/calculators/floor-transition-strip-calculator.json" }, { "slug": "weatherstripping-calculator", "json": "https://craftquantities.com/api/v1/calculators/weatherstripping-calculator.json" }, { "slug": "door-window-casing-calculator", "json": "https://craftquantities.com/api/v1/calculators/door-window-casing-calculator.json" } ], "confusions": [ { "question": "What is a level threshold, and why is it hard?", "answer": "It is an external doorway with essentially no step — accessibility guidance limits the upstand to a very small dimension — and it is hard because it asks one detail to do two contradictory things. A threshold keeps water out by being higher than the water, and a level threshold is not allowed to be. The resolution is drainage rather than height: a drainage channel immediately outside, a falls arrangement taking water away, and often a proprietary threshold with a concealed drained chamber. That is a considerably more expensive detail than a step, it requires the external level to be set correctly during construction rather than adjusted afterwards, and it is the single most common source of water ingress at an accessible entrance. Specifying a level threshold without the drainage is specifying a leak." }, { "question": "Why does an external door need a pan or a tray beneath it?", "answer": "Because the threshold is a horizontal joint at the bottom of a wall, which is where water collects and where it has the longest time to find a way in. Any water that gets past the door's own weathering — driven rain, a failed seal, snow melting against the frame — lands on the structure directly under the threshold, and without something to catch it, it soaks into the floor structure or the wall below. American practice answers with a SILL PAN: a preformed or site-formed tray with upturned back and ends, sealed to the drainage plane, that catches whatever gets through and returns it outward. British practice detailed the same thing as a cavity tray with stop ends. Either way the failure is identical when it is missing, and it appears as rot in the floor beside the door rather than as a visible leak." }, { "question": "How is the internal transition different from the external one?", "answer": "It is doing a finish job rather than a weathering one, and it is sized by the two floors it joins. An internal threshold — the saddle, the transition strip, the door bar — bridges between two coverings that may differ in thickness, in how they move, and in what they need at their edge. A floating floor needs its expansion gap maintained at the doorway, so the strip has to cover a gap rather than clamp the floor; a carpet needs gripping; tile needs its edge protected. That is why transition strips come in families rather than as one product, and why running a floating floor straight through a doorway under a decorative strip that pins it is one of the commonest causes of a floor peaking further into the room." } ], "related": [ "cill", "window-type" ] }, { "slug": "hardstanding", "concept": "Hardstanding and paved area", "family": "site", "definition": "A made-up area of ground constructed to carry vehicles, plant or stored materials, as distinct from a footpath or a landscaped surface. Defined as much by what it is for as by what it is made of.", "url": "https://craftquantities.com/glossary/hardstanding/", "names": [ { "market": "UK", "term": "hardstanding", "alsoCalled": [ "hard standing", "hardstand", "paved area", "driveway" ], "exactness": "absent", "note": "A planning term as much as a construction one. Creating one between a house and the highway engages permitted development rules about permeability and surface water." }, { "market": "AU", "term": "hardstand", "alsoCalled": [ "hardstand area", "paved area", "crossover" ], "exactness": "close", "note": "Common in civil and industrial usage for a made-up area taking plant or storage, with crossover naming the section between the property and the road." }, { "market": "US", "term": "(no single term)", "alsoCalled": [ "pad", "apron", "paved area", "driveway", "hardscape" ], "exactness": "absent", "note": "Named by function instead: a PAD for equipment, an APRON at a garage or an airfield, HARDSCAPE for the paved element of a landscape scheme. No word covers all of them." }, { "market": "CA", "term": "(no single term)", "alsoCalled": [ "pad", "apron", "hardscape", "parking area" ], "exactness": "absent", "note": "As the United States, with frost depth governing the construction of anything that carries a vehicle." } ], "standards": [ { "market": "UK", "standard": "Approved Document H3 / BS 7533", "covers": "Rainwater drainage including surface water from paved areas, and the structural design of pavements constructed with modular units." }, { "market": "US", "standard": "ASCE 58 / ACI 330R", "covers": "Structural design of pavements, and guide for the design and construction of concrete parking lots." } ], "calculators": [ { "slug": "driveway-calculator", "json": "https://craftquantities.com/api/v1/calculators/driveway-calculator.json" }, { "slug": "paver-base-calculator", "json": "https://craftquantities.com/api/v1/calculators/paver-base-calculator.json" }, { "slug": "gravel-driveway-calculator", "json": "https://craftquantities.com/api/v1/calculators/gravel-driveway-calculator.json" } ], "confusions": [ { "question": "Why is paving a front garden a regulated act in Britain?", "answer": "Because of where the water goes, not because of the paving. Replacing a permeable front garden with an impermeable surface sends rainfall that used to soak into the ground into the drainage system instead, and enough of those in a catchment changes how it floods. British permitted development rules therefore allow a hardstanding to be created without planning permission only if the surface is permeable, or if the water is directed to a permeable area within the property rather than to the highway — above a modest threshold area. That makes the DRAINAGE strategy the planning question and the construction a consequence of it, which is the reverse of how most people approach it. A block-paved drive draining to the road is the common case that needs permission and rarely has it." }, { "question": "What actually makes a surface permeable?", "answer": "The whole construction, not the top layer, and this is where permeable paving schemes most often fail. A permeable pavement works as a system: units with enlarged joints or voids, filled with a clean single-size aggregate that stays open; a laying course of the same; a sub-base of open-graded material that both spreads the load and stores water; and a subgrade able to accept it, or an outlet if it cannot. Using ordinary jointing sand instead of the specified clean grit closes the joints within a season. Using a conventional well-graded sub-base — which is designed to compact to a dense, interlocked layer with few voids — leaves nowhere for the water to go. So a permeable surface laid on a conventional base is an impermeable pavement with a permeable top, and it behaves like one in the first heavy rain." }, { "question": "What thickness does it need, and what decides it?", "answer": "The subgrade and the traffic, in that order, and neither is the paving. The subgrade's strength — how much the ground beneath will deform under load — sets how much construction is needed above it to spread a wheel load to something it can take, and that is why the same driveway needs far more sub-base over soft clay than over gravel. Traffic then sets how much: a domestic car is a small fraction of the load a delivery lorry applies, and a hardstanding that will take a skip lorry or a motorhome is a different pavement from one taking a hatchback. The commonest domestic failure is neither: it is omitting the edge restraint, which lets the whole field creep sideways under braking and turning until the joints open and the surface loses its interlock." } ], "related": [ "tarmac" ] }, { "slug": "arris", "concept": "Arris and edge treatment", "family": "materials", "definition": "The sharp edge formed where two surfaces meet, and by extension the act of easing that edge slightly so it does not chip, cut, or hold a coating badly.", "url": "https://craftquantities.com/glossary/arris/", "names": [ { "market": "UK", "term": "arris", "alsoCalled": [ "arrised edge", "eased edge", "pencil round", "chamfer", "arris rail" ], "exactness": "false-friend", "note": "Also a verb — to arris an edge is to ease it. And an ARRIS RAIL is the triangular-section rail in a close-boarded fence, which is a component and not an edge at all." }, { "market": "AU", "term": "arris", "alsoCalled": [ "arrised", "pencil round", "eased edge", "arris rail" ], "exactness": "close", "note": "As the UK, and arris rail is equally standard in Australian fencing, so the component sense of the word travels alongside the edge sense." }, { "market": "US", "term": "edge", "alsoCalled": [ "eased edge", "chamfer", "pencil edge", "arris" ], "exactness": "absent", "note": "Arris appears in stone and specification writing and rarely on site. The instruction is given as eased edge, pencil edge or chamfer — each of which names a specific profile rather than the general act." }, { "market": "CA", "term": "edge", "alsoCalled": [ "eased edge", "chamfer", "bullnose" ], "exactness": "absent", "note": "As the United States, with named profiles rather than a general term for easing." } ], "standards": [ { "market": "UK", "standard": "BS 1186-3 / BS EN 1340", "covers": "Workmanship in joinery including edge treatment, and concrete kerb units where the arris profile is part of the specification." }, { "market": "US", "standard": "ACI 117 / AWI Quality Standards", "covers": "Tolerances for concrete construction including edge condition, and architectural woodwork edge profiles." } ], "calculators": [ { "slug": "tile-edge-profile-calculator", "json": "https://craftquantities.com/api/v1/calculators/tile-edge-profile-calculator.json" }, { "slug": "edge-trim-linear-footage-calculator", "json": "https://craftquantities.com/api/v1/calculators/edge-trim-linear-footage-calculator.json" }, { "slug": "brick-calculator", "json": "https://craftquantities.com/api/v1/calculators/brick-calculator.json" } ], "confusions": [ { "question": "Why ease an edge at all?", "answer": "Because a perfectly sharp edge is the weakest part of almost any material and the worst place for a coating. On CONCRETE and stone, a sharp arris is a thin wedge of material with no support behind it, so it spalls off at the first knock and takes a visible chip with it — which is why kerbs, steps and precast units are specified with a chamfer or a radius. On TIMBER, a sharp edge cannot hold paint: the film thins as it pulls away from the corner, so the coating fails at the arris first and lets water into the end grain behind it. That is the real reason joinery is arrised before priming, and it is why an edge sanded after painting has solved nothing. On METAL and glass it is a safety matter, and on tile it is what an edge profile exists to provide." }, { "question": "What is the difference between arrising, chamfering and a bullnose?", "answer": "How much material comes off, and they are three specifications rather than three words. ARRISING or easing takes the sharpness off and nothing more — a pass with abrasive, leaving an edge that is no longer a blade but still reads as square. A PENCIL ROUND is a small consistent radius, roughly the radius of a pencil, and reads as a deliberately softened edge. A CHAMFER is a flat cut at an angle, usually 45 degrees, and reads as a bevel with two new arrises of its own. A BULLNOSE is a full half-round. Each looks different at a metre, each takes a different amount of time, and a drawing that says eased edge and gets a chamfer has received a visible design change." }, { "question": "What is an arris rail, and why is it that shape?", "answer": "It is the horizontal rail in a close-boarded fence, and it is triangular in section — essentially a square section cut diagonally — with the flat face toward the boards and the apex toward the ground. The shape does two things. It sheds water: there is no upward-facing flat surface for rain to sit on, which is what rots a rectangular rail from the top. And it uses the material efficiently, giving depth where the bending happens while removing the material doing least work. It is one of the more elegant traditional sections, and it is why an arris rail is a stocked item in Britain and a fence rail is a plain rectangle almost everywhere else — different word, different shape, same job done less well." } ], "related": [ "timber" ] }, { "slug": "cistern", "concept": "Cistern and water storage", "family": "services", "definition": "A vessel holding water at atmospheric pressure, filled through a float-operated valve. Covers the small one behind a WC and the large one in a roof space, which do the same thing at different scales.", "url": "https://craftquantities.com/glossary/cistern/", "names": [ { "market": "UK", "term": "cistern", "alsoCalled": [ "WC cistern", "cold water storage cistern", "header tank", "feed and expansion tank" ], "exactness": "false-friend", "note": "Three referents. The WC cistern, the cold water storage cistern in the loft, and the small feed-and-expansion tank for an open-vented heating circuit — all called tanks in speech and all cisterns in a specification." }, { "market": "AU", "term": "cistern", "alsoCalled": [ "toilet cistern", "rainwater tank", "header tank" ], "exactness": "close", "note": "Cistern almost always means the WC component, with rainwater tank the dominant sense of stored water." }, { "market": "US", "term": "tank", "alsoCalled": [ "toilet tank", "cistern", "rainwater cistern", "storage tank" ], "exactness": "false-friend", "note": "The WC component is a TANK. Cistern has drifted almost entirely to rainwater harvesting, so a cistern specification in American usage is usually about collecting rain rather than about plumbing a building." }, { "market": "CA", "term": "tank", "alsoCalled": [ "toilet tank", "cistern", "holding tank" ], "exactness": "false-friend", "note": "As the United States, with holding tank a further distinct meaning in off-grid and septic contexts." } ], "standards": [ { "market": "UK", "standard": "Water Supply (Water Fittings) Regulations / BS EN 14124", "covers": "Backflow protection and air gaps at cisterns, and inlet valves for cisterns with float-operated shut-off." }, { "market": "US", "standard": "ASME A112.19.5 / IPC Chapter 4", "covers": "Flush valves and fill valves for water closets, and plumbing fixture requirements." } ], "calculators": [ { "slug": "toilet-water-usage-calculator", "json": "https://craftquantities.com/api/v1/calculators/toilet-water-usage-calculator.json" }, { "slug": "greywater-cistern-peak-inflow-calculator", "json": "https://craftquantities.com/api/v1/calculators/greywater-cistern-peak-inflow-calculator.json" }, { "slug": "water-leak-cost-calculator", "json": "https://craftquantities.com/api/v1/calculators/water-leak-cost-calculator.json" } ], "confusions": [ { "question": "Why does a British house have a tank in the loft when a modern one does not?", "answer": "Because of how the supply was arranged, and the change is one of the clearest generational divides in domestic plumbing. A traditional INDIRECT system fed the incoming main to the kitchen tap and then to a storage cistern in the roof, and everything else — the bathroom taps, the WC, the hot water cylinder — drew from that cistern under gravity. The reasons were historical: it buffered a supply that could not be relied on for pressure or continuity, and it protected the main from backflow. The costs are the ones that ended it: pressure limited by the height of the loft, a large vessel of standing water in an unheated space, and a serious escape-of-water risk. A modern mains-pressure system — a combi or an unvented cylinder — deletes the cistern entirely, which is why a loft conversion so often begins with removing one." }, { "question": "What is a header tank, and is it the same thing?", "answer": "It is a cistern doing a specific job for a heating circuit, and it is much smaller. An open-vented heating system needs somewhere for the water to expand into as it heats, and somewhere to top up from as it loses a little — so a small feed-and-expansion cistern sits above the system, usually in the loft, connected by a feed pipe and an open vent pipe. It is not a water supply and its contents are not drinkable: the same water circulates through radiators and back. Calling it a header tank is common and slightly misleading, because a header in pipework elsewhere means a manifold. A SEALED system replaces it with an expansion vessel — a pressurised diaphragm vessel doing the same job in a fraction of the space and with no open water at all." }, { "question": "Why is there an air gap above the cistern's inlet?", "answer": "To stop stored water being drawn back into the mains, which is the whole reason cistern inlet valves look the way they do. If the mains supply loses pressure — a burst in the street, a hydrant opened — pressure can reverse and siphon water backward out of anything connected to it. A cistern full of standing water, possibly in a loft, possibly with something in it, is exactly what must not travel back into a drinking supply. So the inlet discharges ABOVE the water surface across a specified vertical gap, and the gap is a physical impossibility rather than a device that can fail. It is why an inlet valve that has been set too high, or a cistern overfilled so the water reaches the inlet, is a regulatory breach and not a nuisance." } ], "related": [ "hot-water-cylinder" ] }, { "slug": "party-wall", "concept": "Party wall and separating wall", "family": "structure", "definition": "A wall shared between two properties in different ownership, or standing astride the boundary between them. It has to carry both buildings, resist fire spreading between them, and limit sound passing through.", "url": "https://craftquantities.com/glossary/party-wall/", "names": [ { "market": "UK", "term": "party wall", "alsoCalled": [ "separating wall", "compartment wall", "party fence wall", "party structure" ], "exactness": "false-friend", "note": "SEPARATING WALL is the Building Regulations term for the fire and sound performance; PARTY WALL is the legal term under the Party Wall etc. Act 1996. The same wall, two different regimes with different definitions." }, { "market": "AU", "term": "party wall", "alsoCalled": [ "common wall", "separating wall", "fire wall" ], "exactness": "close", "note": "Construction requirements under the NCC as elsewhere, without an equivalent of the English notice-and-award statute." }, { "market": "US", "term": "party wall", "alsoCalled": [ "common wall", "demising wall", "fire wall", "fire barrier" ], "exactness": "false-friend", "note": "DEMISING WALL is the commercial term for the boundary between tenancies. FIRE WALL has a precise code meaning — structurally independent, full height — that a party wall may or may not meet." }, { "market": "CA", "term": "party wall", "alsoCalled": [ "common wall", "demising wall", "firewall" ], "exactness": "close", "note": "As the United States, with the same firewall distinction under the National Building Code." } ], "standards": [ { "market": "UK", "standard": "Approved Document E / Party Wall etc. Act 1996", "covers": "Resistance to the passage of sound between dwellings, and the notice, dissent and award procedure for work to a party structure." }, { "market": "US", "standard": "IBC 706 / ASTM E90", "covers": "Fire walls: structural stability, continuity and openings, and laboratory measurement of airborne sound transmission loss." } ], "calculators": [ { "slug": "mlv-soundproofing-calculator", "json": "https://craftquantities.com/api/v1/calculators/mlv-soundproofing-calculator.json" }, { "slug": "acoustic-sealant-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/acoustic-sealant-volume-calculator.json" }, { "slug": "cmu-equivalent-thickness-calculator", "json": "https://craftquantities.com/api/v1/calculators/cmu-equivalent-thickness-calculator.json" } ], "confusions": [ { "question": "Why does work near a party wall in England need notice?", "answer": "Because a statute makes it a process rather than a courtesy, and the process has a timetable that governs when work can start. The Party Wall etc. Act 1996 covers three things: work directly to a party structure — cutting into it, raising it, underpinning it; building a new wall at or astride the boundary; and excavating within defined distances of a neighbour's structure below the level of their foundations. Each requires written notice to the adjoining owner, with a stated period for them to consent or dissent, and dissent means surveyors are appointed and an award is made setting out how the work proceeds and who pays for what. The practical consequences are calendar ones: notice periods run in months, and a loft conversion or a basement that assumed a start date without them is late before it begins. No equivalent statute exists in the other three markets." }, { "question": "Is a party wall the same as a fire wall?", "answer": "Not automatically, and in American code usage the distinction is precise enough to matter. A FIRE WALL in the IBC sense is structurally independent: it is designed so that a collapse on one side does not bring it down, which is what allows the two sides to be treated as separate buildings for code purposes. A party wall may be a fire wall, or it may be a fire BARRIER or a separating wall that achieves a fire resistance period without that independence. British practice frames it differently again, as a compartment wall with a required fire resistance and a requirement for continuity to the underside of the roof covering. The consequence when reading a drawing across markets is that party wall describes ownership, and the fire performance is a separate specification that has to be stated rather than inferred." }, { "question": "Why is sound the hardest part to get right?", "answer": "Because most of it does not go through the wall. A separating wall's laboratory performance assumes sound passing through the wall itself, and in a real building a large share arrives by FLANKING: through the floor that runs continuously under both sides, through a ceiling void that is shared, along a continuous screed, through a service penetration, around the edge of the wall at the external skin. That is why the British regulations test COMPLETED buildings rather than accepting a wall specification, why a wall that measures well in isolation can fail on site, and why remedial work on noise between houses so often has to address the floor rather than the wall everybody is complaining about. A sealed, unpenetrated, structurally isolated junction is usually worth more than extra mass in the wall." } ], "related": [ "cavity-wall", "sound-rating", "firestopping" ] }, { "slug": "suspended-floor", "concept": "Suspended ground floor and crawlspace", "family": "structure", "definition": "A ground floor carried on joists over a void rather than bearing on the ground, with the void between the floor and the earth beneath managed for moisture — historically by ventilating it.", "url": "https://craftquantities.com/glossary/suspended-floor/", "names": [ { "market": "UK", "term": "suspended timber floor", "alsoCalled": [ "suspended floor", "underfloor void", "sleeper wall", "honeycomb wall" ], "exactness": "false-friend", "note": "Names the FLOOR. A SLEEPER or HONEYCOMB wall is the low dwarf wall built with gaps in it to carry the joists mid-span while letting air pass — a component with no standard American name." }, { "market": "AU", "term": "suspended floor", "alsoCalled": [ "subfloor", "underfloor space", "bearers and joists" ], "exactness": "false-friend", "note": "SUBFLOOR in Australian usage means the whole space and structure beneath the floor, where American usage means the sheet material you walk on before the finish goes down." }, { "market": "US", "term": "crawlspace", "alsoCalled": [ "crawl space", "vented crawlspace", "conditioned crawlspace", "pier and beam" ], "exactness": "false-friend", "note": "Names the SPACE. And current American practice increasingly SEALS and conditions that space, which is the opposite of the ventilation British practice depends on." }, { "market": "CA", "term": "crawlspace", "alsoCalled": [ "crawl space", "heated crawlspace" ], "exactness": "close", "note": "As the United States, with sealing and heating the space the normal approach given the frost depth and the winter humidity ratio." } ], "standards": [ { "market": "UK", "standard": "Approved Document C / BS 8103-1", "covers": "Site preparation and resistance to moisture including underfloor ventilation, and structural design of low-rise buildings." }, { "market": "US", "standard": "IRC R408 / ASHRAE 62.2", "covers": "Under-floor space ventilation and the conditions for an unvented conditioned crawlspace, and residential ventilation." } ], "calculators": [ { "slug": "crawlspace-liner-calculator", "json": "https://craftquantities.com/api/v1/calculators/crawlspace-liner-calculator.json" }, { "slug": "rim-joist-insulation-calculator", "json": "https://craftquantities.com/api/v1/calculators/rim-joist-insulation-calculator.json" }, { "slug": "ceiling-joist-linear-footage-calculator", "json": "https://craftquantities.com/api/v1/calculators/ceiling-joist-linear-footage-calculator.json" } ], "confusions": [ { "question": "Ventilate the void or seal it — why do the markets disagree?", "answer": "Because they are solving for different climates and different moisture sources, and both positions are coherent. The BRITISH approach ventilates: airbricks through the external wall on at least two opposite sides give a cross-flow that carries away moisture evaporating from the ground, and blocking them is one of the most reliable ways to rot a floor. That works in a mild, damp climate where outdoor air is rarely much wetter than the void. The AMERICAN approach increasingly SEALS: a ground-covering vapour barrier, sealed vents, insulation at the foundation walls, and the space brought inside the building's thermal envelope. That works where summer outdoor air is far more humid than the cool void, so ventilating it CONDENSES moisture into the space rather than removing it. Applying either approach in the other's climate produces the failure it was designed to prevent." }, { "question": "What is a sleeper wall, and why is it built with gaps?", "answer": "It is a low wall in the void, part-way across the span, carrying a wall plate that the joists sit on — so the joists span from external wall to sleeper wall rather than the full width of the room, which lets a much smaller section be used. It is built HONEYCOMB, with the bricks spaced so there are openings right through it, because a solid wall across the void would block the cross-ventilation the whole floor depends on. Every sleeper wall also sits on its own footing with a damp-proof course under the plate. Two things go wrong with them in practice: the honeycomb gets filled in during later work, which kills the airflow beyond it, and the DPC under the plate is omitted or bridged, which rots the plate the joists are sitting on." }, { "question": "Why does insulating one of these floors go wrong so often?", "answer": "Because the insulation is usually added from below without changing anything else, and it alters the void's behaviour in two ways at once. It makes the void COLDER, since the heat leaking down from the house was quietly keeping it above the dew point — so the same outdoor air that was harmless before now condenses in it. And it frequently obstructs the airflow the ventilation depends on, because insulation fitted between joists is pushed toward the eaves of the void or tucked into the airbricks. The result is a floor that was dry for a century and rots within a few years of being improved. The fix is not to avoid insulating; it is to treat the void's ventilation, the ground covering and the insulation as one system rather than adding one of the three." } ], "related": [ "joist", "airbrick", "subfloor" ] }, { "slug": "airbrick", "concept": "Airbrick and underfloor ventilator", "family": "envelope", "definition": "A perforated unit the size of a brick or a block, built into a wall to ventilate the space behind it — most often the void beneath a suspended timber ground floor.", "url": "https://craftquantities.com/glossary/airbrick/", "names": [ { "market": "UK", "term": "airbrick", "alsoCalled": [ "air brick", "telescopic vent", "periscope vent", "subfloor vent" ], "exactness": "close", "note": "A TELESCOPIC or periscope vent is the version that carries the opening through a cavity wall and up over a raised external level, which is what the plain unit cannot do." }, { "market": "AU", "term": "subfloor vent", "alsoCalled": [ "air vent", "airbrick", "vermin-proof vent" ], "exactness": "close", "note": "Vermin-proofing is a standard requirement rather than an option, and the required free area is prescribed against the subfloor's plan area." }, { "market": "US", "term": "foundation vent", "alsoCalled": [ "crawlspace vent", "automatic vent", "flood vent" ], "exactness": "false-friend", "note": "A FLOOD VENT looks similar and does something else entirely: it lets floodwater in and out of an enclosure so hydrostatic pressure does not collapse the wall, and it is sized by enclosure area under flood rules." }, { "market": "CA", "term": "crawlspace vent", "alsoCalled": [ "foundation vent", "air vent" ], "exactness": "close", "note": "As the United States, and frequently omitted entirely where the crawlspace is sealed and heated instead of ventilated." } ], "standards": [ { "market": "UK", "standard": "Approved Document C / BS 5250", "covers": "Resistance to moisture including the ventilation of under-floor voids, and management of moisture in buildings." }, { "market": "US", "standard": "IRC R408.1 / ASCE 24", "covers": "Under-floor ventilation openings and their required net area, and flood-resistant design where flood openings are required instead." } ], "calculators": [ { "slug": "crawlspace-liner-calculator", "json": "https://craftquantities.com/api/v1/calculators/crawlspace-liner-calculator.json" }, { "slug": "attic-ventilation-calculator", "json": "https://craftquantities.com/api/v1/calculators/attic-ventilation-calculator.json" }, { "slug": "rain-screen-ventilation-area-calculator", "json": "https://craftquantities.com/api/v1/calculators/rain-screen-ventilation-area-calculator.json" } ], "confusions": [ { "question": "Why does blocking one rot a floor?", "answer": "Because the void under a suspended timber floor has a continuous supply of moisture from the ground and only one way to lose it. Water evaporates from the earth beneath the floor all year; the airbricks let outside air pass through and carry it away, and the flow depends on there being openings on at least two opposite sides so air crosses rather than stalls. Block them — with a raised patio, a render coat, a new path, a flower bed, an extension across one elevation, insulation pushed against them from inside — and the humidity in the void rises to the point where timber takes up water faster than it dries. Rot follows over a few seasons, and it starts at the joist ends where they enter the wall, which is the last place anyone looks. It is the single most common way a sound floor is destroyed by an improvement." }, { "question": "What is the free area, and why is it not the hole size?", "answer": "Free area is the actual open area for airflow, after the perforations, the grille and any mesh are taken off the nominal size — so an airbrick's free area is a fraction of the rectangle it occupies, and two units of identical external size can differ substantially. Guidance is expressed as free area per length of wall, or as a proportion of the floor area, which is why a specification counts free area rather than counting bricks. It also explains a common failure: replacing a clear old cast-iron airbrick with a fine-mesh plastic one for vermin-proofing can cut the free area sharply, and doing that to every opening on a house reduces the void's ventilation without a single opening being blocked." }, { "question": "What does a telescopic vent do that an ordinary airbrick cannot?", "answer": "Two things, and both are about geometry rather than airflow. It carries the opening ACROSS a cavity without letting the cavity connect to the void — a plain airbrick in a cavity wall opens into the cavity, which both loses the airflow and lets cavity moisture into the floor void. And it carries the opening UP, so the external face can sit above a raised ground or patio level while the internal face stays at the void. That second use is the common one on an older house, where paths and patios have been laid over decades and the original airbricks now sit at or below the new external level. Fitting one is the correct answer to an airbrick that has been buried; digging a small trench in front of the old one is the answer that fills with leaves." } ], "related": [ "suspended-floor" ] }, { "slug": "engineering-brick", "concept": "Engineering brick and brick durability grades", "family": "materials", "definition": "A brick specified for performance rather than appearance — high compressive strength and low water absorption — used where a wall is heavily loaded, permanently wet, or acting as a barrier to moisture.", "url": "https://craftquantities.com/glossary/engineering-brick/", "names": [ { "market": "UK", "term": "engineering brick", "alsoCalled": [ "Class A", "Class B", "blue brick", "Staffordshire blue" ], "exactness": "absent", "note": "Defined by BOTH strength and water absorption together — Class A at the higher strength and lower absorption, Class B below it. No American grade combines the two properties this way." }, { "market": "AU", "term": "engineering brick", "alsoCalled": [ "exposure grade", "solid brick", "class A" ], "exactness": "close", "note": "EXPOSURE GRADE is the durability classification in Australian practice and is about salt attack and weathering rather than the strength-plus-absorption pair." }, { "market": "US", "term": "(no direct equivalent)", "alsoCalled": [ "SW grade", "severe weathering", "hard-fired brick", "sewer brick" ], "exactness": "absent", "note": "ASTM grades SW, MW and NW classify WEATHERING resistance only. Compressive strength is specified separately, so an American specification has to state both where a British one names a class." }, { "market": "CA", "term": "(no direct equivalent)", "alsoCalled": [ "SW grade", "severe weathering", "clay paver" ], "exactness": "absent", "note": "As the United States under CSA, with severe weathering effectively the default given the freeze-thaw exposure." } ], "standards": [ { "market": "UK", "standard": "BS EN 771-1 / BS 3921 legacy", "covers": "Clay masonry units including compressive strength and water absorption, with the Class A and B engineering designations." }, { "market": "US", "standard": "ASTM C62 / ASTM C216", "covers": "Building brick and facing brick, graded SW, MW and NW by weathering exposure with strength specified separately." } ], "calculators": [ { "slug": "brick-calculator", "json": "https://craftquantities.com/api/v1/calculators/brick-calculator.json" }, { "slug": "brick-ira-calculator", "json": "https://craftquantities.com/api/v1/calculators/brick-ira-calculator.json" }, { "slug": "masonry-pier-axial-capacity-calculator", "json": "https://craftquantities.com/api/v1/calculators/masonry-pier-axial-capacity-calculator.json" } ], "confusions": [ { "question": "What actually makes a brick an engineering brick?", "answer": "Two numbers together, which is what makes the class untranslatable. British classification sets a minimum compressive strength AND a maximum water absorption, and a brick has to meet both to carry the designation — Class A is the more demanding pair, Class B the less. The combination is the point: strength alone gives you a hard brick that still soaks up water and fails in frost, and low absorption alone gives you a dense brick that may not carry load. American grading splits those properties across two clauses of two different standards, so a specification there names a weathering grade and a compressive strength separately and a reader has to check both. Asking a US supplier for a Class B engineering brick will not produce anything; asking for a minimum strength and an SW grade with a stated absorption limit will." }, { "question": "Where is an engineering brick actually required?", "answer": "Where the masonry is either heavily loaded or permanently wet, and often both. The classic British uses are below the damp-proof course, where the wall is in contact with wet ground and cannot be allowed to wick; in manholes and inspection chambers, where it is wet and occasionally under traffic; in retaining structures; and under a heavy concentrated load such as a beam bearing or a pier. The low absorption is doing the work in the wet cases and the strength in the loaded ones. It is worth knowing the reverse too: engineering brick is a poor choice for a general facing wall built in lime mortar, because a brick far denser than its mortar reverses the sacrificial relationship the wall depends on, which is the same mechanism that makes a cement repair destroy soft brickwork." }, { "question": "Why does a brick's suction matter as much as its strength?", "answer": "Because it decides whether the mortar sets or is robbed. A brick's initial rate of absorption — how fast it draws water out of the mortar it is bedded on — governs the bond between the two. A very absorbent brick laid dry pulls water out of the mortar before it can hydrate, leaving a weak, dusty joint and a bond that fails under the first frost; that is why highly absorbent bricks are wetted before laying. At the other end, a very dense low-absorption brick such as an engineering brick takes almost nothing, so the mortar stays wet, the bricks float on the bed, and a wall built too fast in them slumps. Both failures come from the same property read from opposite ends, and it is why suction is measured and specified rather than judged by eye." } ], "related": [ "brick-bond", "spalling" ] }, { "slug": "trv", "concept": "Thermostatic radiator valve", "family": "services", "definition": "A self-acting valve on a radiator that senses the air temperature around it and throttles the flow to hold that room near a set point, without any wiring or control system.", "url": "https://craftquantities.com/glossary/trv/", "names": [ { "market": "UK", "term": "TRV", "alsoCalled": [ "thermostatic radiator valve", "rad valve", "smart TRV", "lockshield" ], "exactness": "absent", "note": "Effectively mandatory on new and replacement radiators outside the room holding the main thermostat. The LOCKSHIELD at the other end is a different valve doing a different job — balancing, not control." }, { "market": "AU", "term": "thermostatic radiator valve", "alsoCalled": [ "TRV", "hydronic valve" ], "exactness": "absent", "note": "Present only where hydronic heating is installed, which is a minority of housing, so the component is specialist rather than standard." }, { "market": "US", "term": "(no common term)", "alsoCalled": [ "TRV", "thermostatic valve", "zone valve" ], "exactness": "absent", "note": "Forced air with a single thermostat is the default, so per-emitter control is unusual. A ZONE VALVE is a different device — electrically driven, controlling a whole circuit from a thermostat." }, { "market": "CA", "term": "(no common term)", "alsoCalled": [ "TRV", "zone valve", "radiator valve" ], "exactness": "absent", "note": "As the United States, with hydronic systems more common so TRVs appear more often than south of the border, still without a standard everyday name." } ], "standards": [ { "market": "UK", "standard": "BS EN 215 / Approved Document L", "covers": "Thermostatic radiator valves: requirements and test methods, and conservation of fuel and power in existing dwellings." }, { "market": "US", "standard": "ASHRAE Handbook — HVAC Systems and Equipment", "covers": "Hydronic system control including modulating valves at terminal units." } ], "calculators": [ { "slug": "baseboard-heater-btu-calculator", "json": "https://craftquantities.com/api/v1/calculators/baseboard-heater-btu-calculator.json" }, { "slug": "hvac-thermal-load-calculator", "json": "https://craftquantities.com/api/v1/calculators/hvac-thermal-load-calculator.json" }, { "slug": "radiant-floor-pex-calculator", "json": "https://craftquantities.com/api/v1/calculators/radiant-floor-pex-calculator.json" } ], "confusions": [ { "question": "Does turning it up make the room heat faster?", "answer": "No, and this is the most common misunderstanding about the device. A TRV is a proportional valve that senses ROOM air temperature and reduces flow as the room approaches the set point — it does not change how hot the water is or how fast the radiator delivers heat while the room is still cold. Below the set point the valve is fully open and the radiator is already doing everything it can, so turning the head from 3 to 5 changes nothing about the rate; it only raises the temperature at which the valve starts closing, which means the room ends up warmer later and uses more fuel to stay there. The correct use is to set each room to the temperature that room should hold and leave it, which is precisely the opposite of how a thermostat-style dial invites people to behave." }, { "question": "Why should the room with the main thermostat have no TRV?", "answer": "Because two controls fighting over one room produce a house that never settles. The main room thermostat decides whether the boiler runs at all; a TRV in the same room decides whether that room's radiator gets flow. If the TRV closes first, the room cools, the thermostat calls for heat, and the boiler fires to serve a room whose radiator is shut — so it runs for the rest of the house while the reference room stays cold and the thermostat never satisfies. If the thermostat is satisfied first, the boiler stops regardless of what every other room wants. The convention is therefore one uncontrolled radiator in the thermostat's room, and it is why installing TRVs everywhere as an efficiency measure sometimes makes a house worse." }, { "question": "Why does a TRV get stuck, and what does the fix tell you?", "answer": "Because the pin it operates sits still for months. A TRV works by a capsule expanding against a pin in the valve body, and through the summer that pin is left in one position where scale and deposits settle around it — so at the start of the heating season the head turns and the pin does not move, leaving a radiator stone cold or permanently hot. The fix is usually to take the head off and free the pin, and the fact that it works tells you the valve body is sound and the head is not at fault. It is also the argument for turning every TRV fully open for a period in summer rather than leaving them all shut, which is the opposite of what most people do when the heating goes off." } ], "related": [ "radiator" ] }, { "slug": "self-levelling-compound", "concept": "Self-levelling compound", "family": "finishes", "definition": "A pourable cement or gypsum-based mortar applied in a thin layer over a floor, flowing out to a flat surface so that a covering can be laid on it. A correction layer, not a structural one.", "url": "https://craftquantities.com/glossary/self-levelling-compound/", "names": [ { "market": "UK", "term": "self-levelling compound", "alsoCalled": [ "latex", "levelling screed", "floor levelling compound", "SLC" ], "exactness": "false-friend", "note": "Called LATEX from the polymer additive in older two-part products, which survives as a name for compounds containing no latex at all. Distinct from a SCREED, which is thicker and can be structural." }, { "market": "AU", "term": "self-levelling compound", "alsoCalled": [ "floor leveller", "levelling compound", "topping" ], "exactness": "close", "note": "As the UK, with topping used where the layer is thick enough to be a wearing surface in its own right." }, { "market": "US", "term": "self-leveling underlayment", "alsoCalled": [ "floor leveler", "SLU", "gypsum underlayment", "topping" ], "exactness": "false-friend", "note": "UNDERLAYMENT is heavily overloaded: it also means the membrane under a roof covering, the acoustic mat under a floating floor, and the sheet ply over a subfloor. Three different products, one word." }, { "market": "CA", "term": "self-leveling underlayment", "alsoCalled": [ "floor leveler", "gypcrete", "topping" ], "exactness": "false-friend", "note": "As the United States, with a brand name used generically for gypsum-based pours in the way Hoover is for vacuum cleaners." } ], "standards": [ { "market": "UK", "standard": "BS EN 13813 / BS 8204-1", "covers": "Screed material and floor screeds: properties and requirements, and code of practice for concrete bases and cement sand levelling screeds." }, { "market": "US", "standard": "ASTM F710 / ASTM F2170", "covers": "Preparing concrete floors to receive resilient flooring, and determining relative humidity in concrete slabs using in-situ probes." } ], "calculators": [ { "slug": "self-leveling-underlayment-calculator", "json": "https://craftquantities.com/api/v1/calculators/self-leveling-underlayment-calculator.json" }, { "slug": "floor-drain-screed-calculator", "json": "https://craftquantities.com/api/v1/calculators/floor-drain-screed-calculator.json" }, { "slug": "heated-screed-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/heated-screed-volume-calculator.json" }, { "slug": "finish-level-compound-calculator", "json": "https://craftquantities.com/api/v1/calculators/finish-level-compound-calculator.json" } ], "confusions": [ { "question": "Is it the same as a screed?", "answer": "No, and treating one as the other is a common and expensive substitution. A SCREED is a thicker layer — commonly tens of millimetres — laid and worked to a level, and depending on its type it may be structural, may carry underfloor heating, and may be a wearing surface. A SELF-LEVELLING COMPOUND is a thin correction layer, usually a few millimetres, that flows out under its own weight to remove small deviations before a covering goes down. It has a maximum thickness beyond which it cracks or debonds, it is not designed to bridge a void, and it is not a wearing surface. Using it to correct a floor that is out of tolerance by twenty millimetres means either applying it far thicker than its specification allows or several passes with the cost of each, and the correct answer is usually a screed." }, { "question": "Why does it need a primer when it is mostly water anyway?", "answer": "Because of what the substrate does to that water. A porous base — an old concrete slab, a sand-cement screed, a plywood deck — pulls water out of the compound as it is poured, and a compound that loses its water before it flows and hydrates does two things: it stops flowing, so it does not level, and it cures weak and dusty at the interface, so it debonds. The primer seals the surface enough to control that suction while still leaving a key. The reverse problem exists on a non-porous base — a power-floated slab, an old adhesive residue, a tiled floor — where nothing absorbs and nothing keys, and the primer there is a different product providing grip rather than control. Using the wrong primer, or none, is the single most common cause of a levelling layer lifting in sheets." }, { "question": "Why does moisture in the slab matter so much before pouring?", "answer": "Because the compound and everything above it is a lid. A concrete slab dries slowly from the surface, and a floor covering with an adhesive is a moisture-sensitive assembly sitting directly on it — so a slab still releasing water will push it into the compound, the adhesive and the covering, and the failure appears as lifting vinyl, blown timber or a mouldy smell months later. That is why the American standards here are moisture tests rather than product specifications: measuring relative humidity inside the slab with in-situ probes, or the calcium chloride emission rate. It is also why a levelling compound is not a remedy for a damp slab: it will bond to a damp substrate and then trap the water, which is worse than the uneven floor it was correcting." } ], "related": [ "screed" ] }, { "slug": "downpipe", "concept": "Downpipe and rainwater discharge", "family": "envelope", "definition": "The vertical pipe carrying water from a gutter or an outlet down to a drain, a gully or a soakaway. Sized by the roof area draining to it and by how many outlets that area is split between.", "url": "https://craftquantities.com/glossary/downpipe/", "names": [ { "market": "UK", "term": "downpipe", "alsoCalled": [ "down pipe", "rainwater pipe", "RWP", "hopper head", "shoe" ], "exactness": "close", "note": "A HOPPER HEAD is the open funnel at the top taking several discharges into one pipe; a SHOE is the swan-neck at the bottom directing water into a gully." }, { "market": "AU", "term": "downpipe", "alsoCalled": [ "stormwater downpipe", "rainhead", "spreader" ], "exactness": "close", "note": "RAINHEAD is the Australian equivalent of the hopper head and is specified with an overflow, so a blockage discharges visibly outside rather than backing into the roof." }, { "market": "US", "term": "downspout", "alsoCalled": [ "leader", "conductor", "conductor head", "elbow" ], "exactness": "close", "note": "LEADER and CONDUCTOR both appear in plumbing codes for the same pipe, with conductor more often used where the pipe is inside the building." }, { "market": "CA", "term": "downspout", "alsoCalled": [ "eavestrough", "leader", "extension" ], "exactness": "false-friend", "note": "EAVESTROUGH is the GUTTER, not the downspout — so eavestrough cleaning is work on the horizontal component, and the two are frequently confused in quotations." } ], "standards": [ { "market": "UK", "standard": "BS EN 12056-3 / Approved Document H3", "covers": "Roof drainage layout and calculation, and rainwater drainage requirements for buildings." }, { "market": "US", "standard": "IPC Chapter 11 / SMACNA", "covers": "Storm drainage including the sizing of vertical conductors and leaders by roof area and rainfall rate." } ], "calculators": [ { "slug": "downspout-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/downspout-length-calculator.json" }, { "slug": "gutter-calculator", "json": "https://craftquantities.com/api/v1/calculators/gutter-calculator.json" }, { "slug": "gutter-hanger-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/gutter-hanger-spacing-calculator.json" } ], "confusions": [ { "question": "How is a downpipe sized, and why is rainfall RATE the input rather than annual rainfall?", "answer": "By the peak flow it has to carry, which comes from the roof area draining to it multiplied by a design rainfall INTENSITY — millimetres per hour, not millimetres per year. The distinction matters because drainage fails in the worst few minutes of the worst storm, not in a wet year: a location with modest annual rainfall and intense summer downpours needs larger pipes than a wetter place with steady drizzle. That is why codes publish a design intensity for a location and a return period rather than an annual figure, and why a system copied from one region to another can be undersized without anybody having made an arithmetic error. The second input is how many downpipes the roof is split between, since halving the area each one serves is usually cheaper than enlarging the pipe." }, { "question": "Why does the gutter's outlet position matter as much as the pipe?", "answer": "Because a gutter's capacity depends on where the water leaves it, and the pipe is often not the constraint. A gutter with an outlet at one END behaves as a long channel with all the flow travelling to that point, and its capacity is limited by the depth of water it can hold before overtopping at the far end. The same gutter with a CENTRE outlet serves two shorter runs and carries substantially more, and outlets at both ends more again. Sharp corners, stop ends, and a run that has to negotiate an angle all reduce it further. So a gutter overflowing is very often not a blocked pipe but a run that was always going to overflow at that intensity, and adding a second outlet fixes what cleaning cannot." }, { "question": "Where should the bottom of it discharge?", "answer": "Somewhere that takes the water away from the building, and the three normal answers have different consequences. Into a trapped GULLY connected to a surface water drain is the conventional arrangement and the one that needs the trap kept wet. Into a SOAKAWAY disperses it into the ground and is subject to how fast that ground accepts water and how far it is from the building. Onto a SHOE discharging over a path is the cheapest and puts a concentrated stream against the base of the wall every time it rains, which saturates the masonry there and is a common cause of damp at low level. The version that causes most damage is none of these: a downpipe that discharges into a drain which is blocked or broken below ground, so the water goes into the ground immediately beside the foundation and nobody can see it." } ], "related": [ "gutter" ] }, { "slug": "wet-room", "concept": "Wet room and curbless shower", "family": "finishes", "definition": "A bathroom in which the floor is tanked and falls to a drain, so the shower has no tray and no upstand and the whole floor is designed to be wetted.", "url": "https://craftquantities.com/glossary/wet-room/", "names": [ { "market": "UK", "term": "wet room", "alsoCalled": [ "wetroom", "level access shower", "tanked floor", "walk-in shower" ], "exactness": "false-friend", "note": "Names the ROOM, and the defining feature is that the floor is the tray. A WALK-IN shower may still have a low tray, so the two are commonly conflated and are different specifications." }, { "market": "AU", "term": "wet area", "alsoCalled": [ "wet room", "hobless shower", "waterproofed area" ], "exactness": "false-friend", "note": "WET AREA is a regulatory classification covering any area requiring waterproofing — a whole bathroom, a laundry — rather than the level-floor shower arrangement specifically." }, { "market": "US", "term": "curbless shower", "alsoCalled": [ "barrier-free shower", "zero-threshold shower", "wet room" ], "exactness": "false-friend", "note": "CURBLESS names the shower, not the room. And American wet room has a second meaning — a shower and tub inside one glazed enclosure — which is a layout rather than a waterproofing strategy." }, { "market": "CA", "term": "curbless shower", "alsoCalled": [ "barrier-free shower", "roll-in shower" ], "exactness": "close", "note": "As the United States, with roll-in used where wheelchair access is the driver and the dimensions are set by accessibility rules." } ], "standards": [ { "market": "UK", "standard": "BS 5385-4 / Approved Document M", "covers": "Design and installation of ceramic tiling in specific conditions including wet environments, and accessible bathrooms." }, { "market": "US", "standard": "ANSI A118.10 / TCNA Handbook", "covers": "Load-bearing bonded waterproof membranes, and tile installation methods including curbless shower assemblies." } ], "calculators": [ { "slug": "waterproofing-membrane-roll-calculator", "json": "https://craftquantities.com/api/v1/calculators/waterproofing-membrane-roll-calculator.json" }, { "slug": "floor-drain-screed-calculator", "json": "https://craftquantities.com/api/v1/calculators/floor-drain-screed-calculator.json" }, { "slug": "crack-isolation-membrane-calculator", "json": "https://craftquantities.com/api/v1/calculators/crack-isolation-membrane-calculator.json" } ], "confusions": [ { "question": "What makes a wet room different from a bathroom with a big shower?", "answer": "The floor is the tray, and that changes the construction rather than the fittings. A conventional bathroom relies on a shower tray or an enclosure to contain the water, so the floor outside it only has to survive splashes. In a wet room there is no containment: water reaches the whole floor, so the whole floor has to be tanked with a continuous waterproof membrane, dressed up the walls to a height, sealed at every penetration, and laid to falls toward a drain. The failure mode is correspondingly different too — a leaking shower tray shows itself at the tray, while a wet room failure delivers water into the structure under the entire room and often appears on a ceiling below, a long way from the shower." }, { "question": "Why are the falls harder than they look?", "answer": "Because the floor has to slope in two dimensions toward one point while remaining level enough to stand a piece of furniture on and to meet the doorway flush. That means a shallow fall — typically a small percentage — formed either by a proprietary pre-formed tray sunk into the floor, or by laying the screed to a shaped fall around the drain, and it has to be accurate: too little and water stands or travels the wrong way, too much and the floor is uncomfortable and tiles are hard to lay. On a timber floor it is harder again, because forming the fall usually means cutting into or building up on the joists, and the drain needs depth below the floor for its trap and its fall to the waste — which is often the constraint that decides whether a wet room is possible at all on an upper storey." }, { "question": "Where do they actually fail?", "answer": "At the junctions and the penetrations, almost never in the middle of the membrane. The recurring list is short and consistent: the joint between floor and wall, where the membrane has to turn a corner and is most likely to be stretched or unbonded; around the drain body, where the membrane has to be clamped rather than merely stuck; at the doorway, where the tanking has to stop and the falls have to hold water back without a threshold; and at every pipe, fixing and screw that passes through. The second family is movement — a timber floor that deflects under a person's weight will crack a rigid membrane and its tiles, which is why a wet room over joists usually calls for a decoupling layer and a stiffer floor than the room had." } ], "related": [ "tanking" ] }, { "slug": "movement-joint", "concept": "Movement, control and expansion joints", "family": "structure", "definition": "A deliberate discontinuity accommodating dimensional change — thermal, moisture, or long-term — so that the change does not crack the material at a place nobody chose.", "url": "https://craftquantities.com/glossary/movement-joint/", "names": [ { "market": "UK", "term": "movement joint", "alsoCalled": [ "expansion joint", "contraction joint", "day joint", "slip plane" ], "exactness": "false-friend", "note": "Umbrella term. Underneath it, an EXPANSION joint is a real gap that closes as a material grows; a CONTRACTION or control joint is an induced weakness that decides where a shrinking material cracks. Opposite purposes." }, { "market": "AU", "term": "control joint", "alsoCalled": [ "articulation joint", "movement joint", "expansion joint" ], "exactness": "false-friend", "note": "ARTICULATION JOINT is the Australian term for a full-depth joint in masonry allowing differential movement, and it is not the same as a sawn control joint in a slab." }, { "market": "US", "term": "control joint", "alsoCalled": [ "contraction joint", "expansion joint", "isolation joint", "sawcut" ], "exactness": "false-friend", "note": "CONTROL joint induces a crack where you want it; EXPANSION joint provides room to grow; ISOLATION joint separates one element from another entirely. Three different details routinely called by each other's names." }, { "market": "CA", "term": "control joint", "alsoCalled": [ "contraction joint", "expansion joint", "isolation joint" ], "exactness": "false-friend", "note": "As the United States, with the same three-way confusion between control, expansion and isolation joints in everyday site usage." } ], "standards": [ { "market": "UK", "standard": "PD 6697 / BS 8204-2", "covers": "Movement joint provision and spacing in masonry, and concrete wearing surfaces including joint layout." }, { "market": "US", "standard": "ACI 224.3R / TMS 402", "covers": "Joints in concrete construction, and movement joint requirements for masonry." } ], "calculators": [ { "slug": "concrete-control-joint-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-control-joint-spacing-calculator.json" }, { "slug": "masonry-control-joint-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/masonry-control-joint-spacing-calculator.json" }, { "slug": "expansion-joint-filler-calculator", "json": "https://craftquantities.com/api/v1/calculators/expansion-joint-filler-calculator.json" }, { "slug": "perimeter-joint-width-calculator", "json": "https://craftquantities.com/api/v1/calculators/perimeter-joint-width-calculator.json" }, { "slug": "sidewalk-joint-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/sidewalk-joint-spacing-calculator.json" } ], "confusions": [ { "question": "What is the difference between a control joint and an expansion joint?", "answer": "They solve opposite problems, and the words are used interchangeably by almost everybody. A CONTROL or contraction joint is a deliberate line of weakness — a sawcut, a formed groove, a bead — cut into something that is going to SHRINK. Concrete shrinks as it cures and a slab will crack; the joint decides where, so the crack happens in a straight tooled line instead of wandering across the floor. It carries no gap and it is not meant to open much. An EXPANSION joint is a genuine gap, filled with a compressible material, in something that is going to GROW — clay brickwork expands irreversibly for years after firing, and a long elevation with nowhere to grow will spall or bow. Cutting a control joint where an expansion joint is needed leaves no room; filling an expansion joint solidly removes the room it was providing." }, { "question": "Why does clay brickwork expand and concrete block shrink?", "answer": "Because they start from opposite states. Clay bricks come out of the kiln bone dry and then slowly take moisture back out of the air, expanding irreversibly over years — most of it in the first months, but never quite stopping. Concrete blocks are made wet and cure by hydrating, then dry out and SHRINK. So a clay elevation needs room to grow and a blockwork one needs somewhere to crack, and a wall with both leaves needs both details in different places. It is also why joint spacing guidance differs by material rather than being one number, and why a long clay elevation built hard against a return with no joint is one of the most reliable ways to produce vertical cracking near the corner." }, { "question": "Why is an isolation joint different again?", "answer": "Because it separates two elements entirely rather than accommodating movement within one. A slab cast hard against a column, a wall, a machine base or a drain runs into a restraint that does not move with it, so the slab cracks at that point whatever joints it has elsewhere. An isolation joint — a compressible strip full depth around the obstruction — lets the slab move independently of it. The distinguishing question is whether the joint is INSIDE one element controlling its own behaviour, or BETWEEN two elements that will behave differently. Getting that wrong produces the classic radial cracks running away from a column in an otherwise well-jointed floor." } ], "related": [ "screed", "sealant" ] }, { "slug": "cavity-tray", "concept": "Cavity tray and through-wall flashing", "family": "envelope", "definition": "A barrier built into a cavity above any obstruction, sloping upward from the outer leaf to the inner one, catching water running down the cavity and directing it back out through weep holes above the obstruction.", "url": "https://craftquantities.com/glossary/cavity-tray/", "names": [ { "market": "UK", "term": "cavity tray", "alsoCalled": [ "DPC tray", "stepped cavity tray", "preformed tray", "stop end" ], "exactness": "close", "note": "STOP ENDS at each end of the tray are part of the detail, not an accessory: without them the collected water runs off the end of the tray into the cavity again and appears somewhere unrelated." }, { "market": "AU", "term": "cavity flashing", "alsoCalled": [ "cavity tray", "flashing", "damp course" ], "exactness": "close", "note": "Cavity flashing is the common term with the same function, and it is required above every opening and at every cavity interruption in masonry veneer construction." }, { "market": "US", "term": "through-wall flashing", "alsoCalled": [ "cavity flashing", "wall flashing", "drip edge", "end dam" ], "exactness": "false-friend", "note": "THROUGH-WALL sounds external and is not — it is inside the wall, running from the drainage plane to beyond the outer face. END DAM is the American name for a stop end and serves the same purpose." }, { "market": "CA", "term": "through-wall flashing", "alsoCalled": [ "cavity flashing", "end dam", "drip edge" ], "exactness": "false-friend", "note": "As the United States, with the flashing required to extend beyond the face of the veneer with a drip so the water leaves rather than tracking back." } ], "standards": [ { "market": "UK", "standard": "Approved Document C / BS 8215", "covers": "Resistance to moisture, and the design and installation of damp-proof courses in masonry including cavity trays." }, { "market": "US", "standard": "TMS 402 Chapter 12 / ASTM E2112", "covers": "Anchored veneer flashing requirements, and the installation of exterior windows, doors and skylights including end dams." } ], "calculators": [ { "slug": "cavity-wall-weep-hole-calculator", "json": "https://craftquantities.com/api/v1/calculators/cavity-wall-weep-hole-calculator.json" }, { "slug": "opening-flashing-membrane-calculator", "json": "https://craftquantities.com/api/v1/calculators/opening-flashing-membrane-calculator.json" }, { "slug": "wall-tie-density-calculator", "json": "https://craftquantities.com/api/v1/calculators/wall-tie-density-calculator.json" } ], "confusions": [ { "question": "Where does a cavity tray have to go?", "answer": "Above every point where something interrupts the cavity, and the list is longer than people expect: over every window and door lintel, at the junction where a lower roof abuts a wall, above an airbrick or a duct passing through, where a cavity is closed at a change of construction, and at the base of the cavity itself. The reasoning is mechanical rather than regulatory — water crossing the outer leaf runs down the inside of it, and anything that blocks the cavity becomes a shelf that water collects on. Without a tray it collects on the obstruction, saturates the masonry around it, and eventually bridges to the inner leaf. That is why damp caused by a missing tray appears at ONE CONSISTENT HEIGHT indoors, typically just above a window, rather than rising from the floor or coming from above." }, { "question": "Why do stop ends matter so much?", "answer": "Because without them the tray does not drain, it diverts. A cavity tray collects water and slopes it toward the outer leaf, and weep holes above the obstruction let it out — but the tray is a shallow channel, and water runs along it to the lowest available exit. If the ends are open, the easiest exit is off the end of the tray and back into the cavity beyond the obstruction, where there are no weep holes and nothing to catch it. So an installation with a correctly fitted tray, correctly placed weeps and no stop ends delivers water into the cavity a metre from where it started, and the damp appears somewhere that makes no sense until somebody opens the wall. American practice names the same component END DAM, which describes what it does rather better." }, { "question": "Can one be retrofitted?", "answer": "Yes, and it is disruptive enough that it is worth establishing the diagnosis first. Retrofitting means removing a course or two of the outer leaf along the length needed, cleaning the cavity out at that level, inserting the tray with its stop ends, forming the weep holes, and rebuilding — usually in short sections so the wall above is supported throughout. Proprietary systems exist for the common cases, particularly over an abutment. The reason to be sure first is that a missing tray, a bridged cavity from mortar droppings, and a failed lintel DPC all produce damp at a similar height, and only one of them is fixed by a tray. Opening a short length of wall to look is often cheaper than guessing." } ], "related": [ "weep-hole" ] }, { "slug": "hardwood-softwood", "concept": "Hardwood and softwood", "family": "materials", "definition": "A botanical division, not a measure of hardness. Hardwoods come from broadleaved trees and softwoods from conifers, and the categories overlap so heavily in actual hardness that the names mislead in both directions.", "url": "https://craftquantities.com/glossary/hardwood-softwood/", "names": [ { "market": "UK", "term": "hardwood / softwood", "alsoCalled": [ "broadleaf", "conifer", "deal", "redwood", "whitewood" ], "exactness": "false-friend", "note": "DEAL means sawn softwood of a particular size, not a species. REDWOOD and WHITEWOOD in British timber trade mean European pine and spruce, and redwood has nothing to do with the Californian tree." }, { "market": "AU", "term": "hardwood / softwood", "alsoCalled": [ "eucalypt", "pine", "seasoned hardwood" ], "exactness": "false-friend", "note": "Australian structural hardwood is genuinely dense eucalypt, so the everyday association between the word and the property holds far better locally than it does elsewhere — which makes the trap worse when reading imported specifications." }, { "market": "US", "term": "hardwood / softwood", "alsoCalled": [ "SPF", "SYP", "Doug fir", "poplar" ], "exactness": "false-friend", "note": "SPF is spruce-pine-fir sold as an interchangeable structural group; SYP is southern yellow pine, a softwood harder than several commercial hardwoods. Poplar is a hardwood softer than most softwoods." }, { "market": "CA", "term": "hardwood / softwood", "alsoCalled": [ "SPF", "Doug fir-larch", "hem-fir" ], "exactness": "false-friend", "note": "As the United States, with SPF the dominant structural group and graded by species combination rather than by single species." } ], "standards": [ { "market": "UK", "standard": "BS EN 338 / BS EN 1912", "covers": "Structural timber strength classes, and the assignment of species and grade combinations to those classes." }, { "market": "US", "standard": "AWC NDS / ASTM D1037", "covers": "Design values for wood construction by species group, and test methods including the Janka hardness test." } ], "calculators": [ { "slug": "board-foot-calculator", "json": "https://craftquantities.com/api/v1/calculators/board-foot-calculator.json" }, { "slug": "lumber-dimensional-size-calculator", "json": "https://craftquantities.com/api/v1/calculators/lumber-dimensional-size-calculator.json" }, { "slug": "timber-beam-bending-stress-calculator", "json": "https://craftquantities.com/api/v1/calculators/timber-beam-bending-stress-calculator.json" } ], "confusions": [ { "question": "If hardwood is not harder, what does the word actually mean?", "answer": "It is a botanical classification about how the tree reproduces and what its cell structure is. HARDWOODS are angiosperms — broadleaved trees whose seeds are enclosed, with a cell structure containing vessels or pores. SOFTWOODS are gymnosperms — conifers with exposed seeds and a simpler structure of tracheids and no vessels. Neither says anything about density or hardness, and the counter-examples are extreme: balsa, the lightest commercial timber in the world, is a hardwood; yew and pitch pine are softwoods harder than oak in places. The practical consequence is that a specification saying hardwood has named a botanical group containing timbers that differ from each other by a factor of ten in density, and has not specified a material." }, { "question": "How should hardness actually be specified?", "answer": "By the property being relied on, and there are several and they are not the same. JANKA hardness measures resistance to denting and is the right figure for a floor that will take furniture and heels. DENSITY predicts weight, screw-holding and how much a section will move with moisture. STRENGTH CLASS — C grades for softwood and D grades for hardwood under the European system, or design values by species group in North America — is what a structural member is selected on and combines bending strength, stiffness and density. DURABILITY class is a separate axis again and is about resistance to decay, which matters outdoors and is unrelated to hardness. A specification naming a strength class and a durability class has said something; one naming hardwood has not." }, { "question": "Why is timber sold by species GROUP rather than by species?", "answer": "Because the mill cannot reliably separate them and the design values are set conservatively for the whole group. SPF — spruce, pine, fir — covers several species that grow intermixed, look similar once sawn, and have similar enough properties that they are graded and marketed together, with design values set by the weakest member. The same logic gives hem-fir and Doug fir-larch in North America and the C classes in Europe, where a class is a performance bracket that many species and grades map into. It is efficient and it has one consequence worth knowing: the timber delivered may be substantially better than the class requires, and none of that margin can be relied on, because the next delivery will be at the bottom of the bracket." } ], "related": [ "timber" ] }, { "slug": "underfloor-heating", "concept": "Underfloor heating", "family": "services", "definition": "Heating delivered through the floor surface rather than from an emitter on the wall. Runs at a much lower temperature than a radiator because the emitting area is the whole room.", "url": "https://craftquantities.com/glossary/underfloor-heating/", "names": [ { "market": "UK", "term": "underfloor heating", "alsoCalled": [ "UFH", "wet underfloor", "electric underfloor", "manifold" ], "exactness": "close", "note": "Usually WET — a pipe circuit fed from a manifold and mixed down from the boiler flow temperature. Electric mats exist and are normally a single-room retrofit rather than a whole-house system." }, { "market": "AU", "term": "in-slab heating", "alsoCalled": [ "hydronic floor heating", "underfloor heating", "slab heating" ], "exactness": "close", "note": "In-slab names where it sits, and the thermal mass of a heated slab is the defining design issue in a climate with large day-night swings." }, { "market": "US", "term": "radiant floor", "alsoCalled": [ "radiant heat", "hydronic radiant", "electric radiant", "PEX" ], "exactness": "false-friend", "note": "RADIANT is the standard word and is partly a misnomer — a heated floor delivers a large share by convection. Electric radiant under a bathroom tile is far more common than a whole-house hydronic system." }, { "market": "CA", "term": "radiant floor", "alsoCalled": [ "in-floor heating", "hydronic radiant", "PEX" ], "exactness": "close", "note": "As the United States, with hydronic whole-house systems more common given the heating season." } ], "standards": [ { "market": "UK", "standard": "BS EN 1264 / BS 8204-1", "covers": "Water-based surface embedded heating: design, installation and heat output, and screeds receiving floor heating." }, { "market": "US", "standard": "ASHRAE Handbook — HVAC Systems / RPA guidelines", "covers": "Panel heating and cooling design, and radiant panel installation practice." } ], "calculators": [ { "slug": "radiant-floor-pex-calculator", "json": "https://craftquantities.com/api/v1/calculators/radiant-floor-pex-calculator.json" }, { "slug": "heated-screed-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/heated-screed-volume-calculator.json" }, { "slug": "radiant-cable-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/radiant-cable-spacing-calculator.json" } ], "confusions": [ { "question": "Why does underfloor heating run so much cooler than a radiator?", "answer": "Because the emitting area is the entire floor rather than a panel on a wall, so the same heat output needs a far smaller temperature difference. A radiator might run at 60 or 70 degrees; a floor runs at 35 to 45 in the pipe and its SURFACE is limited to around 27 to 29 degrees in an occupied room — not by the equipment but by comfort, because a floor warmer than that is unpleasant to stand on and causes complaints. That low flow temperature is also why underfloor heating pairs so well with a heat pump: a heat pump's efficiency falls steeply as its output temperature rises, and a system asking for 40 degrees rather than 70 is asking for its best operating point. It is the single strongest argument for the technology beyond comfort." }, { "question": "Why does it respond so slowly, and what follows from that?", "answer": "Because the floor is a large mass that has to be warmed before the room feels it, and cooled before the room stops feeling it. A screed-embedded system can take hours to respond and continues emitting for hours after it is switched off — which makes the room-thermostat behaviour people are used to actively wrong. Turning it down at night and up in the morning means the floor is cold when the house is occupied and warm when it is not. The correct control strategy is a flatter one: leave it running and let weather compensation adjust the flow temperature, or set back by a small amount rather than switching off. A thin electric mat under a tile is at the other extreme, responding in minutes, which is why the same control advice does not apply to both." }, { "question": "What does it do to the floor covering above it?", "answer": "It constrains it, and this is the part most often discovered too late. Every covering has a maximum surface temperature and a thermal resistance, and a covering that insulates well throttles the whole system: a thick carpet with underlay can halve the output of the floor beneath it, so the system either cannot meet the heat loss or has to run hotter than it should. Timber and engineered boards have a maximum permitted surface temperature and a moisture content they must arrive at, because a heated floor dries them further and they shrink. Tile and stone are the natural partners — low resistance, high tolerance — which is why they dominate. The screed's own commissioning matters too: it has to be brought up to temperature gradually over days before a covering goes down, and doing that after the tiles are laid cracks them." } ], "related": [ "screed" ] }, { "slug": "acrow-prop", "concept": "Adjustable props and shoring", "family": "site", "definition": "A telescopic adjustable post used to support a structure temporarily while it is altered — during a beam installation, an opening being formed, or a slab being cast.", "url": "https://craftquantities.com/glossary/acrow-prop/", "names": [ { "market": "UK", "term": "acrow prop", "alsoCalled": [ "adjustable prop", "prop", "strongboy", "needle", "soldier" ], "exactness": "false-friend", "note": "ACROW is a manufacturer's name used generically. A STRONGBOY is a bracket fitted to a prop to support masonry from a bed joint; a NEEDLE is a beam pushed through a wall and propped each side." }, { "market": "AU", "term": "acrow prop", "alsoCalled": [ "adjustable prop", "shore", "steel prop" ], "exactness": "close", "note": "British terminology with the same generic use of the brand name, under Australian temporary works and formwork standards." }, { "market": "US", "term": "shore", "alsoCalled": [ "post shore", "jack post", "adjustable column", "screw jack" ], "exactness": "false-friend", "note": "A JACK POST sold in a builders' merchant may be a PERMANENT support column rated for a standing load, not a temporary works prop — same shape, different rating and different use." }, { "market": "CA", "term": "shore", "alsoCalled": [ "post shore", "teleposts", "adjustable column" ], "exactness": "false-friend", "note": "TELEPOST is a common Canadian term for the permanent adjustable basement column, so it names the permanent product rather than the temporary one." } ], "standards": [ { "market": "UK", "standard": "BS EN 1065 / BS 5975", "covers": "Adjustable telescopic steel props: product specification and testing, and the procedural control of temporary works." }, { "market": "US", "standard": "ACI 347 / OSHA 1926 Subpart Q", "covers": "Guide to formwork for concrete including shoring and reshoring, and concrete and masonry construction safety requirements." } ], "calculators": [ { "slug": "temporary-needle-prop-load-calculator", "json": "https://craftquantities.com/api/v1/calculators/temporary-needle-prop-load-calculator.json" }, { "slug": "formwork-brace-force-calculator", "json": "https://craftquantities.com/api/v1/calculators/formwork-brace-force-calculator.json" }, { "slug": "steel-baseplate-bearing-calculator", "json": "https://craftquantities.com/api/v1/calculators/steel-baseplate-bearing-calculator.json" } ], "confusions": [ { "question": "What actually decides how many props are needed?", "answer": "The load coming down and what each prop is rated to take AT ITS EXTENDED LENGTH — and that second part is what catches people out. A prop's capacity falls sharply as it is extended, because a longer slender column buckles at a lower load: the same prop rated at several tonnes closed can be rated at a fraction of that near its full extension. So a calculation done on the closed rating and executed at full extension can be out by a factor of several. The load itself is the tributary area of whatever is being supported, including the floors above it, and the wall's self-weight — which for masonry is substantial and routinely underestimated. And each prop needs something to stand on: a prop on a suspended floor is transferring the load to that floor, which then needs propping in turn, all the way to the ground." }, { "question": "What is a strongboy, and why does it exist?", "answer": "It is a bracket that fits the head of a prop with a flat blade projecting sideways, and the blade slides into a bed joint that has been raked out above the working area — so the masonry is supported from a course of brickwork rather than by a plate across its face. It exists because the alternative, a needle, means cutting a hole right through the wall and propping both sides, which is far more work. The limit is that the load path is now a few courses of brickwork above the blade, so the arrangement depends on the masonry above being sound and bonded, and it is not suitable where the wall is in poor condition, where the load is high, or where there is an opening immediately above. That judgement is the reason temporary works are designed rather than arranged." }, { "question": "Why is temporary works a designed activity rather than a site decision?", "answer": "Because the building is at its least stable exactly while it is being propped, and the failures are sudden. A wall with an opening cut in it and no lintel is relying entirely on the props; if one is on soft ground, at too great an extension, not plumb, or missing because the space was awkward, the load redistributes to the others and the sequence runs away. British practice formalises this with a temporary works coordinator and a design for anything non-trivial, and American practice with shoring and reshoring requirements in the formwork standards. The recurring domestic failure is simpler than any of that: propping installed correctly and then removed too early, before the beam has bearing or the concrete has strength." } ], "related": [ "scaffold", "trench-support" ] }, { "slug": "grout", "concept": "Grout", "family": "materials", "definition": "A fluid or semi-fluid cementitious material poured or pressed into a space. What it is for — filling a joint, transferring load, or filling a cavity in masonry — changes it into an entirely different product.", "url": "https://craftquantities.com/glossary/grout/", "names": [ { "market": "UK", "term": "grout", "alsoCalled": [ "tile grout", "non-shrink grout", "grouted cavity", "pointing mortar" ], "exactness": "false-friend", "note": "Three unrelated materials: tile grout fills a joint, non-shrink structural grout transfers load under a baseplate, and grout in a cavity wall or blockwork is a fluid concrete. Not interchangeable in any direction." }, { "market": "AU", "term": "grout", "alsoCalled": [ "tile grout", "core fill", "cementitious grout" ], "exactness": "false-friend", "note": "CORE FILL names the masonry sense specifically, which is clearer than the British usage and separates it from the tiling and structural senses." }, { "market": "US", "term": "grout", "alsoCalled": [ "tile grout", "non-shrink grout", "masonry grout", "sanded grout" ], "exactness": "false-friend", "note": "ASTM separates them by standard: C476 for masonry grout, C1107 for non-shrink structural grout, C1708 for tile grout. Same word, three standards, three products." }, { "market": "CA", "term": "grout", "alsoCalled": [ "tile grout", "core fill", "non-shrink grout" ], "exactness": "false-friend", "note": "As the United States under CSA, with the same three-way split by application and standard." } ], "standards": [ { "market": "UK", "standard": "BS EN 13888 / BS EN 1996-1-1", "covers": "Grout for tiles: classification and requirements, and the design of reinforced masonry including grouted cavities." }, { "market": "US", "standard": "ASTM C476 / ASTM C1107", "covers": "Grout for masonry including slump and aggregate requirements, and packaged dry hydraulic-cement grout (non-shrink)." } ], "calculators": [ { "slug": "grout-calculator", "json": "https://craftquantities.com/api/v1/calculators/grout-calculator.json" }, { "slug": "cmu-cell-grout-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/cmu-cell-grout-volume-calculator.json" }, { "slug": "baseplate-anchor-grout-calculator", "json": "https://craftquantities.com/api/v1/calculators/baseplate-anchor-grout-calculator.json" } ], "confusions": [ { "question": "Why is masonry grout deliberately so wet?", "answer": "Because it has to flow into a narrow cavity full of reinforcement and fill it completely without being vibrated everywhere, and because the dry masonry around it will take the excess water back out. Masonry grout is specified at a slump far higher than would ever be acceptable in structural concrete — the standards call for something close to pourable — and that would normally mean a weak, high water-cement-ratio material. It does not, because the blockwork is absorbent: it draws water out of the grout almost immediately, and the grout in place ends up at a much lower effective water content than it was poured at. That is why grout and concrete cannot be substituted for each other. Concrete at grout's slump is weak concrete; grout at concrete's slump will not fill the cells it was poured into." }, { "question": "What does non-shrink mean, and why does it matter under a baseplate?", "answer": "It means the material does not lose volume as it sets, and under a baseplate that is the entire requirement. A steel column's baseplate transfers its whole load into the foundation through the thin layer between them, and that layer has to be in continuous contact with both faces. Ordinary cementitious material shrinks as it cures — a small percentage, which under a baseplate means a gap, and a gap means the load concentrates on whatever high spots remain. Non-shrink grouts are formulated with expansive agents to compensate, and they are placed from one side so air is pushed out ahead of the flow rather than trapped under the plate. Using ordinary sand-cement mortar under a baseplate is a structural substitution, not an economy." }, { "question": "Sanded or unsanded tile grout — and why does the joint width decide?", "answer": "Sand is there to control shrinkage, and the joint width decides whether it fits. UNSANDED grout is a fine cement paste for joints below about 3 mm — it flows into narrow gaps and does not scratch a polished or soft glazed tile, but in a wide joint it shrinks and cracks because there is no aggregate holding it. SANDED grout carries fine aggregate, which resists shrinkage and is the right choice for wider joints, and it will scratch marble, polished stone and some glass tiles unless a sample is tested first. Epoxy grout is a third family, chemically set rather than cementitious, which is what a laboratory, a commercial kitchen or a heavily used shower gets — far harder to work with, and effectively impervious." } ], "related": [ "cement", "tile-adhesive" ] }, { "slug": "subfloor", "concept": "Subfloor", "family": "structure", "definition": "What is beneath the finished floor — and markets disagree about how far beneath. Either the structural deck bearing on the joists, the whole space and structure under the floor, or simply the surface a covering is bonded to.", "url": "https://craftquantities.com/glossary/subfloor/", "names": [ { "market": "UK", "term": "subfloor", "alsoCalled": [ "floor base", "deck", "substrate", "underfloor void" ], "exactness": "false-friend", "note": "Most often the BASE a covering is laid on — a screed, a slab or a boarded deck — so it is defined by what sits on it rather than by where it is in the structure. SUBSTRATE is the less ambiguous word." }, { "market": "AU", "term": "subfloor", "alsoCalled": [ "underfloor space", "bearers and joists", "subfloor ventilation" ], "exactness": "false-friend", "note": "Names the SPACE and the structure beneath the floor — the void, the bearers, the joists, the stumps. Subfloor ventilation is a standard requirement and refers to that space, not to any sheet." }, { "market": "US", "term": "subfloor", "alsoCalled": [ "subflooring", "deck", "underlayment", "sheathing" ], "exactness": "false-friend", "note": "The structural SHEET fixed to the joists — plywood or OSB. UNDERLAYMENT is then a further thin layer over it for a covering, which is a fourth meaning of a word already overloaded." }, { "market": "CA", "term": "subfloor", "alsoCalled": [ "subflooring", "underlay", "T&G plywood" ], "exactness": "false-friend", "note": "As the United States, with tongue-and-groove sheet the standard product and UNDERLAY used where American usage says underlayment." } ], "standards": [ { "market": "UK", "standard": "BS 8203 / BS 8204-1", "covers": "Installation of resilient floor coverings including base requirements, and concrete bases and screeds to receive flooring." }, { "market": "US", "standard": "IRC R503 / APA Engineered Wood Construction Guide", "covers": "Floor sheathing span ratings and fastening, and panel selection for subfloor applications." } ], "calculators": [ { "slug": "floor-underlayment-roll-calculator", "json": "https://craftquantities.com/api/v1/calculators/floor-underlayment-roll-calculator.json" }, { "slug": "plywood-sheet-calculator", "json": "https://craftquantities.com/api/v1/calculators/plywood-sheet-calculator.json" }, { "slug": "self-leveling-underlayment-calculator", "json": "https://craftquantities.com/api/v1/calculators/self-leveling-underlayment-calculator.json" } ], "confusions": [ { "question": "If a drawing says subfloor, which layer is it?", "answer": "Ask what is above and below it in the same sentence, because the word alone cannot settle it. On an AMERICAN drawing, subfloor is the structural sheet screwed and glued to the joists, and anything between it and the covering is underlayment. On an AUSTRALIAN one, subfloor is the space under the floor, so subfloor ventilation and subfloor inspection are about a void, not a sheet. On a BRITISH one it is usually the surface a covering will bond to, which on a ground floor is a slab or a screed and upstairs is a boarded deck — so the same word means a concrete thing downstairs and a timber one upstairs in the same building. The safe move when writing across markets is to say what it is: the deck, the screed, the slab, or the void." }, { "question": "Why is the subfloor deck glued as well as screwed?", "answer": "Because a nailed or screwed deck squeaks and a glued one does not. A fastener holds the sheet down at a point, and between points the sheet can lift a fraction as the joist shrinks or the floor is walked on — that tiny movement against the fastener shank is the classic floor squeak. A continuous bead of construction adhesive along the joist before the sheet goes down removes the gap entirely, and it also makes the deck act compositely with the joist, which stiffens the floor measurably beyond what either contributes alone. It is why modern practice specifies glued-and-screwed, and why a squeaky deck cannot usually be cured by adding more screws in the same places." }, { "question": "What does the base actually have to do for a floor covering?", "answer": "Be flat enough, dry enough, and sound enough, and those are three separate specifications a covering manufacturer will state. FLATNESS is measured as a deviation over a stated length, and a covering that bridges a hollow will crack or telegraph the defect; that is what levelling compound exists for. DRYNESS is measured, not judged — a slab still releasing moisture will lift an adhesive and blow a timber floor months later. SOUNDNESS means the surface itself is not a bond breaker: a dusting slab, a laitance skin or old adhesive residue will let go with the covering attached to it. Almost every flooring failure traced back honestly turns out to be one of those three rather than the covering." } ], "related": [ "suspended-floor" ] }, { "slug": "sound-rating", "concept": "Sound insulation ratings", "family": "measurement", "definition": "Single-figure numbers summarising how much sound a construction stops. They compress a whole frequency curve into one value, and the rules for doing that differ by market — so the figures are not interchangeable.", "url": "https://craftquantities.com/glossary/sound-rating/", "names": [ { "market": "UK", "term": "Rw", "alsoCalled": [ "DnT,w", "DnT,w + Ctr", "L'nT,w", "sound reduction index" ], "exactness": "false-friend", "note": "Rw is a LABORATORY figure for an element. DnT,w + Ctr is what Approved Document E requires and is measured in the FINISHED building, including flanking — so it is always lower than the lab number." }, { "market": "AU", "term": "Rw", "alsoCalled": [ "Rw + Ctr", "Ln,w", "weighted sound reduction index" ], "exactness": "close", "note": "The ISO system as in the UK, with Rw + Ctr the regulated figure for separating walls and floors under the NCC." }, { "market": "US", "term": "STC", "alsoCalled": [ "sound transmission class", "OITC", "IIC", "FSTC" ], "exactness": "false-friend", "note": "STC is derived differently from Rw: a different frequency range and a different contour-fitting rule. The two are close for many constructions and not equal, and neither converts to the other by arithmetic." }, { "market": "CA", "term": "STC", "alsoCalled": [ "ASTC", "IIC", "sound transmission class" ], "exactness": "false-friend", "note": "ASTC is the apparent STC measured in the FINISHED building including flanking, which is the Canadian counterpart of DnT,w and is the figure the code actually asks for." } ], "standards": [ { "market": "UK", "standard": "Approved Document E / BS EN ISO 717-1", "covers": "Resistance to the passage of sound including pre-completion testing, and the rating of airborne sound insulation in buildings." }, { "market": "US", "standard": "ASTM E90 / ASTM E413", "covers": "Laboratory measurement of airborne sound transmission loss, and the classification for rating sound insulation (STC)." } ], "calculators": [ { "slug": "mlv-soundproofing-calculator", "json": "https://craftquantities.com/api/v1/calculators/mlv-soundproofing-calculator.json" }, { "slug": "multi-stud-wall-stc-estimator", "json": "https://craftquantities.com/api/v1/calculators/multi-stud-wall-stc-estimator.json" }, { "slug": "acoustic-sealant-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/acoustic-sealant-volume-calculator.json" } ], "confusions": [ { "question": "Can an STC figure be converted to an Rw?", "answer": "Not by arithmetic, and the fact that they usually land within a point or two of each other is what makes the assumption dangerous. Both compress a measured curve of sound reduction against frequency into one number by sliding a reference contour until the deviations meet a rule — but the contours differ, the frequency bands included differ, and the rules about how much deviation is allowed differ. For a simple partition the two often agree closely; for constructions with an unusual curve — a lightweight panel with a pronounced dip, a double-glazed unit, a resiliently mounted lining — they can diverge by several points. So a product tested to one system has to be quoted in that system, and a specification asking for Rw is not satisfied by an STC figure however close it looks." }, { "question": "Why is the figure measured in a finished building always lower?", "answer": "Because a laboratory measures the ELEMENT and a building measures the RESULT, and most of the difference is flanking. A lab test isolates a wall between two rooms that share nothing else; a real wall sits in a building with a floor running continuously under it, a ceiling void above it, a screed crossing it, services penetrating it and junctions at every edge. Sound takes all of those routes. That is why British regulation specifies DnT,w + Ctr measured on site rather than accepting a wall specification, why Canada introduced ASTC alongside STC, and why remedial work on noise between dwellings so often has to address the floor or the junctions rather than the wall everybody is complaining about. A wall achieving its lab figure in a building is the exception." }, { "question": "What is Ctr, and why does it change the answer so much?", "answer": "It is a correction that re-weights the rating toward LOW frequencies, and it is included precisely because the single-figure rating without it flatters constructions that are poor at the bass end. The unweighted rating is dominated by mid frequencies — speech — while the noise that actually causes complaints between dwellings is traffic, music and footfall, all of which have most of their energy low down. Ctr is always negative and is larger for lightweight constructions, because mass is what stops low frequencies and a light wall has little. The practical consequence is that a lightweight partition can post a respectable headline figure and a poor one once Ctr is applied, which is exactly the case where occupants report that they can hear the neighbour's television through a wall that passed on paper." } ], "related": [ "party-wall", "impact-sound" ] }, { "slug": "firestopping", "concept": "Firestopping and cavity barriers", "family": "envelope", "definition": "Measures closing the routes fire and smoke take through a building's concealed spaces and through the holes made in fire-resisting elements for services.", "url": "https://craftquantities.com/glossary/firestopping/", "names": [ { "market": "UK", "term": "firestopping", "alsoCalled": [ "cavity barrier", "fire stopping", "intumescent collar", "fire sleeve" ], "exactness": "false-friend", "note": "FIRESTOPPING seals a penetration through an element; a CAVITY BARRIER subdivides or closes a concealed space. Two different requirements in Approved Document B, routinely used as one word." }, { "market": "AU", "term": "fire stopping", "alsoCalled": [ "fire collar", "cavity barrier", "service penetration seal" ], "exactness": "close", "note": "NCC terminology closely follows the British split, with cavity barriers required in concealed spaces and tested penetration systems required at services." }, { "market": "US", "term": "firestopping", "alsoCalled": [ "through-penetration firestop", "fireblocking", "draftstopping", "F rating", "T rating" ], "exactness": "false-friend", "note": "FIREBLOCKING and DRAFTSTOPPING are separate code items covering concealed spaces, and they are about resisting fire SPREAD in a void rather than achieving a rated seal — closer to a cavity barrier than to a firestop." }, { "market": "CA", "term": "firestopping", "alsoCalled": [ "fireblocking", "firestop system", "F/FT rating" ], "exactness": "false-friend", "note": "As the United States, with the National Building Code separating firestopping at penetrations from fireblocking in concealed spaces." } ], "standards": [ { "market": "UK", "standard": "Approved Document B / BS EN 1366-3", "covers": "Fire safety including cavity barriers and the sealing of service penetrations, and fire resistance tests for penetration seals." }, { "market": "US", "standard": "ASTM E814 (UL 1479) / IBC 714 and 718", "covers": "Through-penetration firestop systems with F and T ratings, and fireblocking and draftstopping requirements." } ], "calculators": [ { "slug": "firestop-caulk-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/firestop-caulk-volume-calculator.json" }, { "slug": "membrane-penetration-box-area-calculator", "json": "https://craftquantities.com/api/v1/calculators/membrane-penetration-box-area-calculator.json" }, { "slug": "seal-off-fitting-grout-calculator", "json": "https://craftquantities.com/api/v1/calculators/seal-off-fitting-grout-calculator.json" }, { "slug": "fire-joint-movement-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/fire-joint-movement-volume-calculator.json" }, { "slug": "shaftwall-limiting-height-calculator", "json": "https://craftquantities.com/api/v1/calculators/shaftwall-limiting-height-calculator.json" }, { "slug": "single-sided-fire-rated-board-calculator", "json": "https://craftquantities.com/api/v1/calculators/single-sided-fire-rated-board-calculator.json" } ], "confusions": [ { "question": "What is the difference between a firestop and a cavity barrier?", "answer": "What they are closing. A FIRESTOP seals a hole made in a fire-resisting element — a pipe, a cable bundle, a duct passing through a compartment wall or floor — and its job is to restore that element's rating at the penetration. A CAVITY BARRIER closes or subdivides a concealed space: the gap behind a rainscreen, the void above a suspended ceiling, the space in a timber frame wall, the cavity in a masonry wall at a compartment line. The first is about a hole somebody made; the second is about a void the construction inherently has. They are different products, different tests and different clauses, and a building with perfect firestopping at every penetration and no cavity barriers has an unbroken route for fire through its own voids." }, { "question": "What do the F and T ratings mean, and why are there two?", "answer": "Because a seal can stop flame passing while still letting enough heat through to start a fire on the other side. The F rating is the time the system resists the passage of FLAME and hot gases — the obvious requirement. The T rating is the time before the temperature on the unexposed side rises by a stated amount, which matters because a steel pipe passing through a wall conducts heat along itself and can ignite material touching it on the far side without any flame having passed. So a system can carry a two-hour F rating and a much shorter T rating, and which one a specification needs depends on whether anything combustible can be against the penetration on the unexposed side. A specification quoting only an F rating has not answered that." }, { "question": "Why is a tested SYSTEM specified rather than a product?", "answer": "Because the rating belongs to the whole assembly, not to the sealant. A firestop test covers a specific combination: the element being penetrated and its construction, the service and its material and diameter, the annular gap, the depth and type of the seal, and the way it was installed. Change any of those — a copper pipe instead of steel, a larger gap, a thinner bead, a plasterboard wall of different construction — and the tested system no longer describes what was built, so the rating does not apply. That is why firestopping is documented by system reference rather than by product name, why photographs and labels at each penetration are standard practice on any building that will be inspected, and why filling a hole with a tube of something fire-rated is not firestopping." } ], "related": [ "party-wall", "fire-door" ] }, { "slug": "insulation-batt", "concept": "Batt, quilt and insulation roll", "family": "materials", "definition": "Flexible fibrous insulation — mineral wool or glass wool — installed by friction fit between framing members or laid over a ceiling. Sold either pre-cut to a bay length or as a roll to be cut on site.", "url": "https://craftquantities.com/glossary/insulation-batt/", "names": [ { "market": "UK", "term": "quilt", "alsoCalled": [ "insulation roll", "loft roll", "slab", "batt", "mineral wool" ], "exactness": "false-friend", "note": "A British SLAB is a rigid or semi-rigid mineral wool board, not a concrete slab and not the same as a quilt. Loft roll is sold by roll length and cut on site rather than pre-cut to a bay." }, { "market": "AU", "term": "batts", "alsoCalled": [ "insulation batts", "blanket", "ceiling batts" ], "exactness": "close", "note": "American terminology and format, with batts pre-cut for the local framing module rather than sold as roll." }, { "market": "US", "term": "batt", "alsoCalled": [ "blanket", "faced batt", "unfaced batt", "roll" ], "exactness": "false-friend", "note": "A FACED batt carries a kraft or foil facing acting as a vapour retarder and a stapling flange — a specification decision about which side it goes, and there is no direct British equivalent product." }, { "market": "CA", "term": "batt", "alsoCalled": [ "blanket", "friction fit", "unfaced batt" ], "exactness": "close", "note": "As the United States, with unfaced batts more common because a separate continuous polyethylene air/vapour barrier is normally specified instead of a facing." } ], "standards": [ { "market": "UK", "standard": "BS EN 13162 / Approved Document L", "covers": "Factory-made mineral wool products for thermal insulation, and conservation of fuel and power." }, { "market": "US", "standard": "ASTM C665 / IECC", "covers": "Mineral-fiber blanket thermal insulation for light frame construction, and the energy code's required R-values by assembly and climate zone." } ], "calculators": [ { "slug": "insulation-batt-calculator", "json": "https://craftquantities.com/api/v1/calculators/insulation-batt-calculator.json" }, { "slug": "mineral-wool-batt-calculator", "json": "https://craftquantities.com/api/v1/calculators/mineral-wool-batt-calculator.json" }, { "slug": "attic-insulation-upgrade-calculator", "json": "https://craftquantities.com/api/v1/calculators/attic-insulation-upgrade-calculator.json" } ], "confusions": [ { "question": "Does compressing it into the bay reduce its performance?", "answer": "Yes for compression into a shallower space, no for slight lateral squeeze, and the distinction is the one people get backwards. Fibrous insulation works by trapping still air, and the thermal resistance comes mostly from the THICKNESS of that trapped air layer — so squashing a 100 mm quilt into a 75 mm space gives you roughly the resistance of 75 mm, not of 100. But a batt slightly wider than the bay, compressed laterally so it grips the studs, keeps its full thickness and simply has a slightly higher density, which is a negligible change and is exactly how a friction fit is meant to work. The failure that actually costs performance is neither: it is a batt cut short, left with gaps at the ends, or with the ends not touching, because a small gap short-circuits a large area." }, { "question": "Faced or unfaced, and which way does the facing go?", "answer": "Toward the warm side in winter, which in most of North America means toward the interior — and that is the rule, not a preference. The facing on a faced batt is a vapour retarder, there to slow water vapour moving from warm humid air into the cold part of the assembly where it would condense. Put it on the cold side and it does the opposite: it traps moisture in the insulation. That is also why British practice generally uses unfaced quilt with a separate vapour control layer, and why Canadian practice specifies a continuous polyethylene air/vapour barrier rather than relying on the facings. The facing's stapling flange is a convenience; its position is a building-physics decision, and in a mixed or hot-humid climate the correct answer may be no vapour retarder at all." }, { "question": "Why does a wall never achieve the batt's R-value?", "answer": "Because the studs are not insulation and they run right through. A timber stud has perhaps a quarter of the thermal resistance of the insulation beside it, and in a wall at 400 mm centres with headers, sills, corners and junctions the framing is a substantial fraction of the wall area — commonly a fifth to a quarter in real construction rather than the tenth people assume. Heat takes the easy path, so the wall's whole-assembly U-value is far worse than the batt's nominal R-value suggests. That is why energy codes have moved to assembly performance and continuous exterior insulation rather than cavity R-value alone: a layer outside the framing interrupts every one of those bridges at once, which no amount of better batt can do." } ], "related": [ "r-value" ] }, { "slug": "plinth", "concept": "Plinth and toe kick", "family": "finishes", "definition": "Either the removable board closing the gap beneath a run of kitchen or bathroom units, or the projecting base of a wall, a column or a structure. One word, two unrelated components.", "url": "https://craftquantities.com/glossary/plinth/", "names": [ { "market": "UK", "term": "plinth", "alsoCalled": [ "kickboard", "kick board", "plinth block", "base course" ], "exactness": "false-friend", "note": "Also the projecting base of a wall or column, and a PLINTH BLOCK is a third thing again — the small block at the foot of an architrave where it meets the skirting." }, { "market": "AU", "term": "kickboard", "alsoCalled": [ "plinth", "toe kick", "kicker" ], "exactness": "close", "note": "Kickboard is the standard joinery term, which keeps it separate from the architectural plinth in a way British usage does not." }, { "market": "US", "term": "toe kick", "alsoCalled": [ "toekick", "kick plate", "plinth", "base" ], "exactness": "close", "note": "TOE KICK names the kitchen component specifically and PLINTH is reserved for the architectural base, so the two senses do not collide. A KICK PLATE on a door is a fourth thing." }, { "market": "CA", "term": "toe kick", "alsoCalled": [ "kick", "base", "plinth" ], "exactness": "close", "note": "As the United States, with the same separation between the joinery and the architectural senses." } ], "standards": [ { "market": "UK", "standard": "BS 6222 / Approved Document M", "covers": "Domestic kitchen equipment dimensional requirements, and access to and use of buildings including approach and reach at fittings." }, { "market": "US", "standard": "ANSI/KCMA A161.1 / ADA 804", "covers": "Performance and construction standard for kitchen cabinets, and accessible kitchens including clear floor space and knee and toe clearance." } ], "calculators": [ { "slug": "kitchen-remodel-cost-calculator", "json": "https://craftquantities.com/api/v1/calculators/kitchen-remodel-cost-calculator.json" }, { "slug": "baseboard-trim-calculator", "json": "https://craftquantities.com/api/v1/calculators/baseboard-trim-calculator.json" }, { "slug": "cost-per-linear-foot-calculator", "json": "https://craftquantities.com/api/v1/calculators/cost-per-linear-foot-calculator.json" } ], "confusions": [ { "question": "Why is there a recess under kitchen units at all?", "answer": "So you can stand close enough to work at the worktop without your toes hitting the cabinet, which is exactly what the American name says and the British one does not. Standing upright at a bench, a person's feet extend forward of their body; without a recess they have to stand back, which puts the worktop further from them and pushes them into a forward lean for every task. The recess is typically around 100 mm deep and 150 mm high, and those dimensions are not arbitrary — accessibility guidance in both markets specifies toe clearance, and in an accessible kitchen the requirement extends to knee clearance under at least one working position, which is a much deeper recess and changes the cabinetry rather than just the board." }, { "question": "Why is the plinth a separate removable piece rather than part of the carcass?", "answer": "Because it has three jobs the carcass cannot do, and all three need it to come off. It has to be SCRIBED to the floor, which is never level, so it is cut to fit on site after the units are levelled on their legs — a fixed base would either rock or leave a wedge-shaped gap. It has to be REMOVABLE for access to the legs, to a water leak, to a dishwasher's feet and to whatever has rolled under there. And it has to be SEALED at the floor in a wet area, which is a bead that occasionally needs renewing. That is also why a plinth left off, or one with its seal failed, is such a reliable entry for water into a kitchen floor: the gap behind it is open to the whole run." }, { "question": "What is a plinth block, and why did it exist?", "answer": "It is a small block of timber, thicker and usually wider than both, set at the foot of a door architrave where the architrave meets the skirting. It exists because those two mouldings are different thicknesses and different profiles, and joining them directly means scribing one complex shape onto another at a point that takes knocks, gets cleaned and gets kicked. The plinth block takes both: the architrave dies onto its top, the skirting dies onto its side, and neither has to be scribed to the other. It is also more durable at exactly the height where a vacuum cleaner and a mop live. It largely disappeared with simpler mouldings and returned with period restoration, and it is a third meaning of a word that already had two." } ], "related": [ "skirting" ] }, { "slug": "conservatory", "concept": "Conservatory and sunroom", "family": "envelope", "definition": "A largely glazed room attached to a house, thermally separated from it, and exempt from some of the requirements a habitable extension would have to meet — an exemption that depends entirely on that separation.", "url": "https://craftquantities.com/glossary/conservatory/", "names": [ { "market": "UK", "term": "conservatory", "alsoCalled": [ "sunroom", "garden room", "orangery", "lean-to" ], "exactness": "false-friend", "note": "A regulatory category with conditions: a defined floor area, a proportion of glazing, thermal separation from the house, and independent heating controls. A glazed room failing those is an extension, not a conservatory." }, { "market": "AU", "term": "sunroom", "alsoCalled": [ "enclosed verandah", "conservatory", "garden room" ], "exactness": "close", "note": "Named by use rather than by a regulatory carve-out, with the NCC treating an enclosed sunroom as conditioned space if it is heated or cooled." }, { "market": "US", "term": "sunroom", "alsoCalled": [ "four-season room", "three-season room", "solarium", "Florida room" ], "exactness": "false-friend", "note": "THREE-SEASON and FOUR-SEASON is the meaningful American split: three-season is unheated and outside the thermal envelope, four-season is inside it and must meet the energy code like any room." }, { "market": "CA", "term": "sunroom", "alsoCalled": [ "four-season room", "three-season room", "solarium" ], "exactness": "close", "note": "As the United States, with the three- and four-season distinction sharper because an unheated glazed room is unusable for much of the year." } ], "standards": [ { "market": "UK", "standard": "Approved Document L / The Building Regulations Schedule 2", "covers": "Conservation of fuel and power, and the exemptions for conservatories including the thermal separation condition." }, { "market": "US", "standard": "IECC / AAMA 2100", "covers": "Energy code requirements for conditioned space, and voluntary specifications for sunroom products by category." } ], "calculators": [ { "slug": "window-wall-u-factor-calculator", "json": "https://craftquantities.com/api/v1/calculators/window-wall-u-factor-calculator.json" }, { "slug": "window-heat-loss-savings-calculator", "json": "https://craftquantities.com/api/v1/calculators/window-heat-loss-savings-calculator.json" }, { "slug": "btu-cooling-calculator", "json": "https://craftquantities.com/api/v1/calculators/btu-cooling-calculator.json" } ], "confusions": [ { "question": "What actually makes something a conservatory rather than an extension?", "answer": "Conditions, not appearance, and the one that gets broken is the separation. British regulations exempt a conservatory from some energy requirements provided it is below a floor area limit, is substantially glazed in its walls and roof, is separated from the house by walls, doors and windows of the same standard as the external envelope, and has its own independent heating controls. Take out the doors to make an open-plan space, or extend the central heating into it, and it is no longer separated — it is now part of the conditioned building, and its glass has to meet the standards a habitable room's envelope would. That is the single most common regulatory problem with conservatories, and it is created after the build by an owner rather than by the installer." }, { "question": "Why is the separation a regulatory condition rather than a preference?", "answer": "Because a conservatory is a very poor thermal envelope, and the exemption exists on the assumption that it is not being heated to living-room temperature all winter. A room with glass walls and a glass roof loses heat far faster per square metre than any compliant wall, and if it is brought inside the heated envelope the whole house's energy performance falls sharply. So the deal the regulations strike is: build it to a lower standard, and keep it separate so the house is not paying for it. Removing the separation takes the benefit of the exemption while removing the condition it was granted under — which is why building control treats it as a change requiring the glazing and the heating to be reconsidered, not as a decorating decision." }, { "question": "What is an orangery, and is it a different thing?", "answer": "Traditionally yes, and in current usage it is mostly a marketing distinction with one real consequence. An orangery historically had substantial masonry piers and a solid roof with a glazed lantern in the middle, rather than a fully glazed roof — it was a building with large windows, not a glass box. That distinction matters because the proportion of GLAZING is one of the conditions for the conservatory exemption: a room with a largely solid roof may fall outside it and be treated as an extension, with the energy requirements that follow. So the word describes a look, and the thing it correlates with — how much of the envelope is glass — is a regulatory input. Anyone specifying one should establish which side of that line the design falls on before it is built rather than after." } ], "related": [ "trickle-vent" ] }, { "slug": "spalling", "concept": "Spalling and scaling", "family": "materials", "definition": "Material breaking away from the face of masonry or concrete. What separates the cases is DEPTH and cause: a thin surface loss, a flake off a brick face, or a piece dislodged by something expanding behind it.", "url": "https://craftquantities.com/glossary/spalling/", "names": [ { "market": "UK", "term": "spalling", "alsoCalled": [ "frost damage", "blown brick", "delamination", "popping" ], "exactness": "close", "note": "A BLOWN brick is one whose fired face has come away leaving the softer body exposed, which then erodes quickly — a specific and common case rather than a general term." }, { "market": "AU", "term": "spalling", "alsoCalled": [ "concrete cancer", "salt attack", "fretting" ], "exactness": "false-friend", "note": "CONCRETE CANCER is the common Australian term for spalling driven by reinforcement corrosion, and FRETTING names the crumbling loss of mortar and soft masonry, which is erosion rather than spalling." }, { "market": "US", "term": "spalling", "alsoCalled": [ "scaling", "delamination", "pop-out", "flaking" ], "exactness": "false-friend", "note": "SCALING is a distinct defined defect: loss of a thin surface layer of concrete, graded by depth and typically from de-icing salts and freeze-thaw. A POP-OUT is a small conical loss over a single unsound aggregate particle." }, { "market": "CA", "term": "spalling", "alsoCalled": [ "scaling", "pop-out", "delamination" ], "exactness": "false-friend", "note": "As the United States, with scaling a routine concern given salt use and the freeze-thaw cycle count." } ], "standards": [ { "market": "UK", "standard": "BS EN 771-1 / BS EN 1504-9", "covers": "Clay masonry units including freeze-thaw durability categories, and the principles for protection and repair of concrete structures." }, { "market": "US", "standard": "ASTM C672 / ACI 201.2R", "covers": "Scaling resistance of concrete surfaces exposed to de-icing chemicals, and guide to durable concrete." } ], "calculators": [ { "slug": "brick-calculator", "json": "https://craftquantities.com/api/v1/calculators/brick-calculator.json" }, { "slug": "tuckpointing-repair-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/tuckpointing-repair-volume-calculator.json" }, { "slug": "concrete-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-calculator.json" } ], "confusions": [ { "question": "What is the difference between spalling and scaling?", "answer": "Depth and mechanism, and the American standards separate them because the repairs differ. SCALING is the loss of a thin surface layer — the mortar skin comes away and the aggregate is exposed, usually graded by how deep it has gone. Its typical cause is freeze-thaw acting on a surface saturated with de-icing salt, and it is a surface durability problem. SPALLING is a piece of material coming OFF, often several centimetres deep, and its typical cause is something behind it expanding: corroding reinforcement, a corroding steel lintel, ice in a saturated brick, or a hard repair restraining a soft substrate. So scaling is about the surface's resistance and spalling is about what is behind it — which is why probing the depth is the first thing to do and why a surface treatment fixes one and hides the other." }, { "question": "Why does reinforcement corrosion spall concrete rather than just weakening it?", "answer": "Because rust takes up several times the volume of the steel it came from, and that expansion happens inside the concrete. Reinforcement is protected by the alkalinity of the surrounding concrete, which passivates the steel — and that protection is lost either when carbonation reaches the bar, or when chlorides do. Once corrosion starts, the expanding rust exerts pressure on the cover concrete from within, and since concrete is weak in tension the cover cracks and then breaks away in a piece, exposing the bar. The exposed bar then corrodes faster. That is why COVER is specified so carefully, why spalling on a concrete structure is treated as urgent rather than cosmetic, and why patching the face without treating the steel simply relocates the same failure to the edge of the patch." }, { "question": "Why does a brick face blow after decades of being fine?", "answer": "Because something changed the water, not the brick. A fired brick has a denser skin and a more porous body, and the skin is what resists frost. It blows when the brick becomes saturated and then freezes — so the trigger is almost always a change in how wet that brick gets: a failed gutter above it, ground level raised against the wall, a cement render or a sealant trapping moisture in, a repointing in a mortar harder than the brick so the wall now dries through the face instead of the joints, or a bed against the wall being watered. That is why blown bricks cluster rather than appearing at random, and why replacing them without finding the water source produces the same failure in the new ones within a few winters." } ], "related": [ "engineering-brick", "efflorescence" ] }, { "slug": "lath", "concept": "Lath and plaster background", "family": "finishes", "definition": "The background a wet plaster or render coat keys into. Historically riven or sawn timber strips with gaps between them; in current practice expanded metal or a specialist board.", "url": "https://craftquantities.com/glossary/lath/", "names": [ { "market": "UK", "term": "lath", "alsoCalled": [ "lath and plaster", "riven lath", "expanded metal lath", "EML", "keys" ], "exactness": "false-friend", "note": "Usually means the historic TIMBER laths and the ceiling they carry. EML is used in current work and is a different material with a different failure mode entirely." }, { "market": "AU", "term": "lath", "alsoCalled": [ "metal lath", "render lath", "lath and plaster" ], "exactness": "close", "note": "Both senses in use, with the historic timber version far less common given the age of the building stock and the dominance of plasterboard." }, { "market": "US", "term": "lath", "alsoCalled": [ "metal lath", "expanded metal lath", "wood lath", "rock lath", "stucco netting" ], "exactness": "false-friend", "note": "Almost always means METAL lath, a current product under stucco and plaster. ROCK LATH is a third thing again — a gypsum board base for a plaster skim, a mid-century transitional product." }, { "market": "CA", "term": "lath", "alsoCalled": [ "metal lath", "wire lath", "stucco lath" ], "exactness": "close", "note": "As the United States, with metal lath standard under stucco and the historic timber sense confined to renovation work." } ], "standards": [ { "market": "UK", "standard": "BS EN 13914-2 / BS 8000-10", "covers": "Design, preparation and application of internal plastering, and workmanship on building sites for plastering and rendering." }, { "market": "US", "standard": "ASTM C847 / ASTM C1063", "covers": "Metal lath, and the installation of lathing and furring to receive interior and exterior portland cement-based plaster." } ], "calculators": [ { "slug": "stucco-lath-calculator", "json": "https://craftquantities.com/api/v1/calculators/stucco-lath-calculator.json" }, { "slug": "plaster-scratch-coat-calculator", "json": "https://craftquantities.com/api/v1/calculators/plaster-scratch-coat-calculator.json" }, { "slug": "ceiling-plasterboard-sheet-calculator", "json": "https://craftquantities.com/api/v1/calculators/ceiling-plasterboard-sheet-calculator.json" } ], "confusions": [ { "question": "How does lath and plaster actually hold itself up?", "answer": "By KEYS, and understanding that explains every failure of it. Timber laths are nailed across the joists with a deliberate gap of a few millimetres between them. The first plaster coat is pushed hard enough to squeeze through those gaps, and the material that comes out the far side slumps over and sets, forming a hook over the back of each lath. Those hooks — the keys — are the entire mechanical support: the plaster is not stuck to the laths, it is hanging on them. So when a ceiling fails, it is because the keys have broken, and they break from vibration, from a leak softening them, from a century of thermal cycling, or from somebody laying insulation on top of them in the loft. The plaster then sits unsupported until something disturbs it, which is why lath-and-plaster ceilings come down in one piece." }, { "question": "Why is metal lath still used when plasterboard exists?", "answer": "Because it does something board cannot: it lets a wet coat be applied to a shape. Expanded metal lath is a sheet slit and stretched into a mesh, and plaster or stucco pushed into it keys through in the same way as the historic timber system — but it bends, so it can follow a curve, wrap a column, form an arch or run over an irregular background. It also provides a base on materials nothing will stick to directly, and reinforces the coat against cracking across a junction between two different backgrounds. That is why stucco in North America is applied over lath as standard and why British render over an awkward background specifies EML. The choice against board is about geometry and continuity, not about tradition." }, { "question": "Why does a repair to a lath-and-plaster ceiling go wrong so often?", "answer": "Because the new work is stiff and the old work moves, and because screwing into it breaks what is holding it up. A common repair is to overboard — fix plasterboard through the old ceiling into the joists — which is sound if the fixings reach the joists and if the extra weight is acceptable, and disastrous if the screws land in laths rather than joists, because they then pull on the very keys that were still working. Patching with modern gypsum plaster onto a lime-plastered ceiling puts a hard, strong material against a soft flexible one, and the junction cracks. And any of it done from below, pushing upward, breaks more keys around the working area. That is why serious lath-and-plaster repair is done by supporting from below and consolidating from ABOVE where access allows." } ], "related": [ "skim" ] }, { "slug": "gauge", "concept": "Gauge", "family": "measurement", "definition": "A number standing in for a dimension. Depending on the trade it means a wire or sheet thickness on an inverted scale, the exposed part of a roofing course, a screw's shank diameter, or a measuring instrument.", "url": "https://craftquantities.com/glossary/gauge/", "names": [ { "market": "UK", "term": "gauge", "alsoCalled": [ "batten gauge", "SWG", "screw gauge", "gauge rod", "gauging" ], "exactness": "false-friend", "note": "BATTEN GAUGE is a roofing distance in millimetres. GAUGING is mixing plaster. SWG is a legacy wire scale differing from the American one. Four unrelated senses before leaving a single site." }, { "market": "AU", "term": "gauge", "alsoCalled": [ "B&S gauge", "batten gauge", "sheet gauge" ], "exactness": "false-friend", "note": "Metric thicknesses in millimetres are now standard for sheet, with gauge surviving in speech and in imported product data — so a gauge number on an Australian job is usually somebody else's scale." }, { "market": "US", "term": "gauge", "alsoCalled": [ "AWG", "sheet metal gauge", "wire gauge", "ga" ], "exactness": "false-friend", "note": "AWG for wire and a SEPARATE sheet metal gauge for steel, and they are different scales: 16 AWG wire and 16 gauge steel have no dimensional relationship at all." }, { "market": "CA", "term": "gauge", "alsoCalled": [ "AWG", "sheet gauge", "mil" ], "exactness": "false-friend", "note": "As the United States, with MIL a further trap — a thousandth of an inch in North American usage, and a millimetre in casual speech elsewhere." } ], "standards": [ { "market": "UK", "standard": "BS 3737 legacy / BS EN 10143", "covers": "Historic standard wire gauge, and continuously hot-dip coated steel sheet thickness tolerances, which are specified in millimetres." }, { "market": "US", "standard": "ASTM B258 / ASTM A480", "covers": "Standard nominal diameters for solid round wires (AWG), and general requirements for flat-rolled stainless and heat-resisting steel, which use decimal inches." } ], "calculators": [ { "slug": "wire-gauge-voltage-drop-calculator", "json": "https://craftquantities.com/api/v1/calculators/wire-gauge-voltage-drop-calculator.json" }, { "slug": "light-gauge-track-linear-footage-calculator", "json": "https://craftquantities.com/api/v1/calculators/light-gauge-track-linear-footage-calculator.json" }, { "slug": "roof-batten-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-batten-spacing-calculator.json" }, { "slug": "awg-to-mm2-calculator", "json": "https://craftquantities.com/api/v1/calculators/awg-to-mm2-calculator.json" }, { "slug": "wire-gauge-to-amperage-calculator", "json": "https://craftquantities.com/api/v1/calculators/wire-gauge-to-amperage-calculator.json" }, { "slug": "extension-cord-gauge-calculator", "json": "https://craftquantities.com/api/v1/calculators/extension-cord-gauge-calculator.json" } ], "confusions": [ { "question": "Why does a bigger gauge number mean thinner material?", "answer": "Because the scale counts drawing operations, not dimensions. Wire was made by pulling it through successively smaller dies, and the gauge number recorded how many times it had been drawn — so more passes meant a thinner wire and a higher number. Sheet gauge has a related history in the number of rolling reductions. The scale is therefore inverted relative to every other dimension on a drawing, and it is not linear either: the step between 10 and 12 is a different physical amount from the step between 20 and 22. That is why a gauge number cannot be scaled, interpolated or converted arithmetically — it has to be looked up in the right table, and the right table depends on the material and the market." }, { "question": "Is 16 gauge wire the same thickness as 16 gauge sheet?", "answer": "No, and they are not even close. AWG 16 wire is about 1.29 mm in diameter; 16 gauge steel sheet is about 1.52 mm thick, and 16 gauge for a non-ferrous sheet is a different figure again because sheet gauge tables are material-specific. There is no relationship between the two scales beyond the coincidence of using numbers. The practical consequence on a mixed job is that gauge is not a unit and cannot be carried between trades: an electrician's 16 and a sheet-metal worker's 16 describe unrelated dimensions. That is also the reason European and Australian practice moved to stating millimetres directly, and why any specification crossing markets is safer quoting the thickness." }, { "question": "What does gauge mean on a roof?", "answer": "A distance, and this is the sense with no relation to any of the others. The batten gauge is the spacing from one tile or slate batten to the next, measured centre to centre, and it equals the covering's length minus the required headlap, divided by the number of courses covering a given tile. It is quoted in millimetres or inches like any other dimension, it rises and falls with the roof pitch because the lap does, and it is what a roofer sets out with a gauge rod. Nothing about it is inverted and nothing about it is a lookup table. The same word in the same conversation may mean the thickness of the flashing lead, the gauge of the fixing nail, and the spacing of the battens — three unrelated quantities." } ], "related": [ "nominal-size", "illuminance" ] }, { "slug": "footing", "concept": "Footing and foundation", "family": "structure", "definition": "The part of a structure that spreads load into the ground. Whether that word covers the spread base only, or the base plus the wall built off it, depends on the market.", "url": "https://craftquantities.com/glossary/footing/", "names": [ { "market": "UK", "term": "foundation", "alsoCalled": [ "strip foundation", "trench fill", "footing", "raft", "pad foundation" ], "exactness": "false-friend", "note": "FOOTING is used loosely for the whole foundation. The named types are the distinction that matters: a strip is a thin band with masonry built off it, trench fill is concrete nearly to ground level." }, { "market": "AU", "term": "footing", "alsoCalled": [ "strip footing", "pad footing", "waffle raft", "stiffened raft", "bored pier" ], "exactness": "close", "note": "FOOTING is the standard term and the site classification by soil reactivity drives the design, which is why waffle rafts and stiffened slabs are common where British practice would dig a trench." }, { "market": "US", "term": "footing", "alsoCalled": [ "spread footing", "foundation wall", "stem wall", "grade beam", "frost footing" ], "exactness": "false-friend", "note": "The FOOTING is the widened base only; the FOUNDATION or STEM WALL is the separate wall built on it. Two elements, two pours, two drawings — where British practice often has one." }, { "market": "CA", "term": "footing", "alsoCalled": [ "spread footing", "foundation wall", "frost wall", "grade beam" ], "exactness": "false-friend", "note": "As the United States, with frost depth governing so strongly that a foundation wall is often a full basement wall simply because the footing has to be that deep anyway." } ], "standards": [ { "market": "UK", "standard": "Approved Document A / BS 8004", "covers": "Structure, and the code of practice for foundations including bearing pressures and minimum depths." }, { "market": "US", "standard": "IRC Chapter 4 / ACI 332", "covers": "Prescriptive footing widths and frost depth requirements for residential work, and residential concrete construction." } ], "calculators": [ { "slug": "spread-footing-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/spread-footing-sizing-calculator.json" }, { "slug": "continuous-footing-grade-beam-calculator", "json": "https://craftquantities.com/api/v1/calculators/continuous-footing-grade-beam-calculator.json" }, { "slug": "footing-bearing-pressure-calculator", "json": "https://craftquantities.com/api/v1/calculators/footing-bearing-pressure-calculator.json" }, { "slug": "post-hole-concrete-calculator", "json": "https://craftquantities.com/api/v1/calculators/post-hole-concrete-calculator.json" }, { "slug": "pier-adfreeze-uplift-calculator", "json": "https://craftquantities.com/api/v1/calculators/pier-adfreeze-uplift-calculator.json" }, { "slug": "post-bearing-area-calculator", "json": "https://craftquantities.com/api/v1/calculators/post-bearing-area-calculator.json" } ], "confusions": [ { "question": "Is a footing the same thing as a foundation?", "answer": "Not in North America, and the difference is two separate concrete elements. There, the FOOTING is the widened pad or strip at the bottom that spreads the load over enough soil, and the FOUNDATION WALL or STEM WALL is the wall built on top of it carrying the structure up to floor level. They are poured separately, reinforced separately, and drawn separately, and a quantity for one is not a quantity for the other. British practice uses the word foundation for the whole assembly and often does not have two elements at all, because trench fill pours concrete nearly to ground level in one operation. So a bill of quantities crossing markets has to establish which elements are being priced before any volume is meaningful." }, { "question": "Why is a trench-fill foundation usually cheaper than a strip?", "answer": "Because it trades a cheap material for expensive labour, and on most sites that trade wins. A traditional strip puts a few hundred millimetres of concrete in the bottom of the trench and then a bricklayer builds masonry up from it to ground level, working down a hole — which is slow, needs the trench wide enough to work in, needs the trench held open and safe while they do it, and needs the excavation battered or supported. Trench fill digs a narrower trench and fills almost all of it with concrete in one pour, so the extra concrete replaces days of below-ground bricklaying and a wider excavation. It is more concrete and less of everything else. The strip comes back into its own where concrete is expensive, where the dig is very deep, or where the trench cannot be kept stable long enough to pour it full." }, { "question": "What sets the depth of a foundation?", "answer": "Whatever moves the ground, and which of those governs is regional. In cold climates it is FROST: the base must sit below the depth to which the ground freezes, because water expanding as it freezes lifts anything above it, and that depth is prescribed locally and can exceed a metre. In shrinkable clay it is MOISTURE: clay swells when wet and shrinks when dry, the active zone extends deeper than frost ever does, and nearby trees make it worse by drawing water out, so depths of a metre and often far more are normal and a removed tree can cause heave for years afterwards. Elsewhere it is simply reaching soil that can carry the pressure. This is why a foundation detail cannot be copied between regions: the same house on the same load needs a different depth for a reason that has nothing to do with the house." } ], "related": [ "reinforcement", "underpinning" ] }, { "slug": "chase", "concept": "Chase and safe zone", "family": "services", "definition": "A groove cut into a wall so a cable or pipe can be buried in it. What limits it is structural on one side and about future drilling on the other.", "url": "https://craftquantities.com/glossary/chase/", "names": [ { "market": "UK", "term": "chase", "alsoCalled": [ "chasing", "safe zone", "prescribed zone", "wall chaser" ], "exactness": "identical", "note": "SAFE ZONE is the term that matters — the bands of a wall where a buried cable may run, so that anyone drilling later knows which strips to avoid." }, { "market": "AU", "term": "chase", "alsoCalled": [ "chasing", "notching", "conduit chase" ], "exactness": "close", "note": "Chasing masonry is limited in the same way, with the practical difference that domestic cable is more often run in conduit within framed or furred walls than buried in solid masonry." }, { "market": "US", "term": "chase", "alsoCalled": [ "notch", "bore", "pipe chase", "raceway" ], "exactness": "false-friend", "note": "A CHASE is more often a vertical shaft carrying services between floors than a groove in a wall. Cutting a stud is a NOTCH or a BORE, and those have their own separate depth limits." }, { "market": "CA", "term": "chase", "alsoCalled": [ "notch", "bore", "service chase" ], "exactness": "false-friend", "note": "As the United States, with notching and boring limits set as fractions of the member's depth and protective plates required where a fastener could reach the cable." } ], "standards": [ { "market": "UK", "standard": "BS 7671 Section 522 / Approved Document A", "covers": "Protection of cables concealed in walls including the permitted zones, and limits on chasing to masonry walls." }, { "market": "US", "standard": "NEC 300.4 / IRC R602.6", "covers": "Protection of cables against physical damage including nail plates, and limits on drilling and notching of studs and plates." } ], "calculators": [ { "slug": "wire-gauge-voltage-drop-calculator", "json": "https://craftquantities.com/api/v1/calculators/wire-gauge-voltage-drop-calculator.json" }, { "slug": "conduit-fill-calculator", "json": "https://craftquantities.com/api/v1/calculators/conduit-fill-calculator.json" }, { "slug": "stud-bore-notch-limit-calculator", "json": "https://craftquantities.com/api/v1/calculators/stud-bore-notch-limit-calculator.json" }, { "slug": "cable-tray-fill-calculator", "json": "https://craftquantities.com/api/v1/calculators/cable-tray-fill-calculator.json" } ], "confusions": [ { "question": "What is a safe zone and why does it exist?", "answer": "It is a band of wall where a buried cable is permitted to run, and it exists so that someone drilling into a wall years later can predict where not to drill. British wiring rules define the zones geometrically: a horizontal band within a set distance of the top of the wall, vertical bands running up and down from an accessory such as a socket or switch, and bands along the corners where two walls meet. A cable outside those zones has to be protected — armoured, in earthed conduit, at sufficient depth, or on a circuit with residual current protection. The zones are not a guarantee, which is why a detector is still the right first move, but they are the reason a cable runs straight up from a socket rather than diagonally to save a metre of cable." }, { "question": "How deep can a chase be cut into a wall?", "answer": "Shallow enough that the wall is still a wall, and the limits are expressed as fractions of its thickness. British guidance allows a vertical chase to about a sixth of the leaf's thickness and a horizontal chase to about a twelfth, and horizontal is more restrictive because it cuts across the direction the load travels — it reduces the section resisting a vertical load along the whole length of the cut, where a vertical chase weakens a narrower strip. Chases must not be cut back to back on opposite faces of the same leaf, must not be cut in a hollow block whose shell is thinner than the chase, and must never be cut into a cavity wall's leaf so deeply that the cavity is broken into. Cutting a chase across a lintel or a padstone is the case that causes real structural damage, because the material removed was doing concentrated work." }, { "question": "Why do American walls need nail plates when British walls need zones?", "answer": "Because the hazard has a different shape in each construction. In a framed wall the cable runs through a bored hole in a stud, so the danger is a fastener driven into that stud face at the height of the hole — the answer is a steel plate over the stud edge, protecting a specific known point. In a solid masonry wall the cable is buried in plaster over a chase and could be anywhere, so the answer is a rule about WHERE it may be, enforced by convention so that drilling elsewhere is reasonably safe. Neither approach transfers: a nail plate is meaningless in masonry because there is no member edge to protect, and a safe zone is weaker in a framed wall because a cable can be pulled through anywhere between the studs. A house using both constructions needs both disciplines, applied to the right walls." } ], "related": [ "ring-final-circuit" ] }, { "slug": "formwork", "concept": "Formwork and shuttering", "family": "structure", "definition": "The temporary mould that holds wet concrete in shape until it can hold itself. Measured by the area of concrete face it forms, not by the volume of concrete it contains.", "url": "https://craftquantities.com/glossary/formwork/", "names": [ { "market": "UK", "term": "formwork", "alsoCalled": [ "shuttering", "shutters", "falsework", "striking", "soldiers" ], "exactness": "identical", "note": "SHUTTERING and formwork are used interchangeably for the mould. FALSEWORK is the separate thing holding the mould up, and STRIKING is taking it off." }, { "market": "AU", "term": "formwork", "alsoCalled": [ "shuttering", "form ply", "stripping", "back-propping" ], "exactness": "identical", "note": "As British practice, with STRIPPING rather than striking in everyday use and a formwork standard that sets the design loads explicitly." }, { "market": "US", "term": "forms", "alsoCalled": [ "formwork", "shoring", "stripping", "form ties", "snap ties" ], "exactness": "close", "note": "FORMS for the mould, SHORING for what holds it up, STRIPPING for removal. Shuttering is not used, and falsework mainly appears in bridge and heavy civil work." }, { "market": "CA", "term": "forms", "alsoCalled": [ "formwork", "shoring", "stripping", "ICF" ], "exactness": "close", "note": "As the United States, with insulating concrete forms common enough in housing that FORMS may mean a permanent part of the wall rather than something removed." } ], "standards": [ { "market": "UK", "standard": "BS 5975 / BS EN 13670", "covers": "Procedural control for falsework including the temporary works coordinator role, and execution of concrete structures." }, { "market": "US", "standard": "ACI 347 / ACI 318", "covers": "Guide to formwork for concrete including design pressures, and building code requirements for structural concrete." } ], "calculators": [ { "slug": "concrete-formwork-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-formwork-calculator.json" }, { "slug": "wall-formwork-pressure-calculator", "json": "https://craftquantities.com/api/v1/calculators/wall-formwork-pressure-calculator.json" }, { "slug": "formwork-tie-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/formwork-tie-spacing-calculator.json" }, { "slug": "column-formwork-pressure-calculator", "json": "https://craftquantities.com/api/v1/calculators/column-formwork-pressure-calculator.json" }, { "slug": "retaining-wall-stem-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/retaining-wall-stem-volume-calculator.json" } ], "confusions": [ { "question": "Why is formwork measured in area when concrete is measured in volume?", "answer": "Because the cost follows the FACE, not the fill. What a formwork item buys is a surface: a sheet of material held rigidly in position, sealed at its edges, treated with a release agent, and taken off again afterwards. Doubling the depth of a slab doubles the concrete and barely changes the formwork, while splitting the same volume of concrete into more and thinner elements multiplies the formwork without changing the concrete at all. That is why a quantity of cubic metres tells you very little about what a concrete element will cost, and why two designs with identical concrete volumes can differ sharply in price. The ratio of formed area to volume is the number worth looking at, and it is worst on thin walls, small isolated bases and anything with a lot of edges." }, { "question": "What actually decides when formwork can be struck?", "answer": "The strength the concrete has reached, which is not the same as the time that has passed — and the difference is temperature. Concrete gains strength through a chemical reaction that runs faster when warm and very slowly when cold, so a striking time that is safe in summer can be badly unsafe in winter on the same mix. The governing question is also different for different parts of the pour: a vertical face carries no load and only needs the concrete stiff enough not to slump or be damaged, so it can come off within a day, whereas the SOFFIT of a slab or a beam is holding the element's own weight and everything on it, and cannot come off until the concrete can carry that itself. This is why striking times are specified against strength, why maturity is monitored in cold weather, and why back-propping keeps load on a young slab after the forms below it are gone." }, { "question": "What pressure does wet concrete put on a wall form?", "answer": "Far more than people expect, and it depends on how fast the pour goes. Wet concrete behaves like a dense liquid, so the pressure at the bottom of a form rises with the height of fluid concrete above it — and concrete is roughly two and a half times as dense as water, so a form a few metres tall sees pressures that will burst an underbuilt panel. What limits it is that concrete stiffens as it sets: once the lower part is no longer fluid it stops transmitting pressure from above, so a SLOW pour in shallow lifts develops much less pressure than a fast one, and cold weather raises the pressure by delaying that stiffening. Vibration temporarily re-liquefies concrete and pushes the pressure back up, which is why over-vibrating a tall form is a common cause of a blow-out. The pour rate is therefore part of the formwork design, not a site decision." } ], "related": [ "slump" ] }, { "slug": "efflorescence", "concept": "Efflorescence", "family": "materials", "definition": "A whitish deposit left on a surface when water carrying dissolved salts evaporates from it. The deposit is a symptom of water movement, not of the material being defective.", "url": "https://craftquantities.com/glossary/efflorescence/", "names": [ { "market": "UK", "term": "efflorescence", "alsoCalled": [ "lime bloom", "white staining", "new build stain", "saltpetring" ], "exactness": "false-friend", "note": "LIME BLOOM is a different deposit — calcium carbonate from lime leaching out of fresh mortar or concrete — which is harder to remove and does not simply wash away as ordinary efflorescence does." }, { "market": "AU", "term": "efflorescence", "alsoCalled": [ "salt attack", "fretting", "white bloom" ], "exactness": "false-friend", "note": "SALT ATTACK names the damaging case where crystallisation erodes the masonry, so the Australian term often implies harm where the British word implies a stain." }, { "market": "US", "term": "efflorescence", "alsoCalled": [ "whiskering", "bloom", "new building bloom", "subflorescence" ], "exactness": "close", "note": "SUBFLORESCENCE is named separately and is the one that matters: the same salts crystallising just below the surface, where the pressure spalls the face instead of staining it." }, { "market": "CA", "term": "efflorescence", "alsoCalled": [ "bloom", "subflorescence", "salt deposit" ], "exactness": "close", "note": "As the United States, with de-icing salt adding a second source that has nothing to do with the masonry's own chemistry." } ], "standards": [ { "market": "UK", "standard": "BS EN 771-1 / BRE Good Building Guide", "covers": "Clay masonry units including active soluble salts content categories, and guidance on removing deposits without damaging the masonry." }, { "market": "US", "standard": "ASTM C67 / ASTM C1400", "covers": "Sampling and testing brick including an efflorescence test, and the guide to cleaning existing masonry." } ], "calculators": [ { "slug": "brick-calculator", "json": "https://craftquantities.com/api/v1/calculators/brick-calculator.json" }, { "slug": "tuckpointing-repair-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/tuckpointing-repair-volume-calculator.json" }, { "slug": "stone-veneer-mortar-calculator", "json": "https://craftquantities.com/api/v1/calculators/stone-veneer-mortar-calculator.json" } ], "confusions": [ { "question": "Is efflorescence a sign of a damp problem?", "answer": "It is a sign of water MOVING, which is not the same thing. Salts do not travel on their own: they dissolve in water inside the material, get carried to a face where the water evaporates, and are left behind. So a deposit tells you water has been in there and has come out here — and on a new wall that is completely normal, because the construction water is drying out and takes a season or two to stop. What makes it a problem is a deposit that keeps returning in the same place year after year, because that means a continuing supply of water rather than the building drying once. The right response is therefore not to attack the deposit but to ask where the water comes from: a leaking gutter, a bridged cavity, ground level above the damp-proof course, a failed flashing. Treat the stain without answering that and it comes back." }, { "question": "Why does washing it off make it worse?", "answer": "Because water is the transport, and a hose supplies more of it. Wetting the wall dissolves the deposit and carries it straight back INTO the masonry, where it waits for the next drying cycle and comes out again — usually looking worse, because more salt has now been mobilised from deeper in. The same mechanism makes pressure washing actively harmful: it drives water in hard, and on a soft brick or lime mortar it also erodes the face, giving the salts a rougher surface to sit on. The recommended order is the opposite of instinct: brush the dry deposit off with a stiff bristle brush, let the wall go through its drying season, and repeat. Where a chemical clean is genuinely needed it is done on a pre-wetted wall with a controlled rinse, because the pre-wetting is what stops the cleaner itself being sucked in." }, { "question": "When is a white deposit actually serious?", "answer": "When it is crystallising behind the face rather than on it, or when it is not efflorescence at all. SUBFLORESCENCE — the American term for the same salts depositing just under the surface — exerts pressure inside the pores as the crystals grow, and that pressure spalls the face off. The tell is a surface that is powdering, flaking or losing its skin rather than merely looking white. The second case is SULFATE ATTACK, where sulfates in solution react with the cement in the mortar itself: the mortar expands, joints crack and the wall can grow measurably taller, and no amount of cleaning touches it because the damage is the chemistry rather than the deposit. The third is LIME BLOOM, calcium carbonate rather than a soluble salt, which does not wash off because it is not soluble in water. Each needs a different answer, so identifying which one is on the wall comes before deciding anything." } ], "related": [ "spalling" ] }, { "slug": "airtightness", "concept": "Airtightness", "family": "envelope", "definition": "How much air leaks through a building's envelope under a test pressure, rather than through the openings provided for it. Measured by pressurising the building and recording the flow needed to hold the pressure.", "url": "https://craftquantities.com/glossary/airtightness/", "names": [ { "market": "UK", "term": "air permeability", "alsoCalled": [ "airtightness", "q50", "air leakage", "air pressure test", "m³/h·m² @50Pa" ], "exactness": "false-friend", "note": "AIR PERMEABILITY divides leakage by the ENVELOPE AREA. It is a different quantity from the air change rate used in North America, not the same quantity in other units." }, { "market": "AU", "term": "air permeability", "alsoCalled": [ "air tightness", "ACH50", "blower door test", "air leakage rate" ], "exactness": "close", "note": "Both conventions appear, with air changes per hour common in voluntary programmes and envelope-area figures in commercial work — so the unit must be stated rather than assumed." }, { "market": "US", "term": "air leakage", "alsoCalled": [ "ACH50", "air changes per hour", "blower door", "CFM50", "envelope tightness" ], "exactness": "false-friend", "note": "ACH50 divides leakage by the internal VOLUME. CFM50 is the raw flow before any division. Neither converts to a British air permeability figure without the building's own area and volume." }, { "market": "CA", "term": "air leakage", "alsoCalled": [ "ACH50", "NLA", "normalized leakage area", "blower door" ], "exactness": "false-friend", "note": "NORMALIZED LEAKAGE AREA expresses the leak as an equivalent HOLE rather than a flow, which is a third convention again and the most intuitive of the three to explain." } ], "standards": [ { "market": "UK", "standard": "ATTMA TSL1 / Approved Document L", "covers": "Measuring air permeability of building envelopes in dwellings, and the maximum permitted figure and testing requirement." }, { "market": "US", "standard": "ASTM E779 / IECC R402.4", "covers": "Determining air leakage rate by fan pressurization, and the prescriptive air leakage limit expressed in air changes per hour at 50 pascals." } ], "calculators": [ { "slug": "blower-door-cfm-target-calculator", "json": "https://craftquantities.com/api/v1/calculators/blower-door-cfm-target-calculator.json" }, { "slug": "air-changes-per-hour-calculator", "json": "https://craftquantities.com/api/v1/calculators/air-changes-per-hour-calculator.json" }, { "slug": "worst-case-depressurisation-calculator", "json": "https://craftquantities.com/api/v1/calculators/worst-case-depressurisation-calculator.json" }, { "slug": "attic-bypass-sealing-material-calculator", "json": "https://craftquantities.com/api/v1/calculators/attic-bypass-sealing-material-calculator.json" } ], "confusions": [ { "question": "Can an ACH50 figure be converted to air permeability?", "answer": "Only for a specific building, and only if you know both its envelope area and its internal volume — which means the conversion is a property of the building, not of the units. Air permeability divides the leakage flow by the area of the envelope through which it leaks; ACH50 divides the same flow by the volume the building encloses. The ratio between the two is therefore volume over area, which is a length: a tall, compact block has a large volume per unit of envelope, a single-storey sprawl has a small one. The practical consequence is that the same physical envelope quality produces a BETTER-looking ACH50 in a compact building and a worse one in a spread-out building, while air permeability is unaffected by shape. So a rule of thumb quoted for converting one to the other is a rule of thumb about typical house shapes, and it fails exactly where the shape is unusual." }, { "question": "Why is the test done at 50 pascals when no building ever sees that?", "answer": "Because it is the smallest pressure at which the answer is repeatable. At the pressure differences a building actually experiences — a few pascals from wind and the stack effect — the flow through the leaks is tiny, and the measurement is swamped by the weather changing while you take it. Raising the pressure to 50 pascals makes the leakage flow large compared with the noise, so two testers on two days get the same answer. Fifty pascals is roughly what a stiff breeze would exert, so it is high enough to be measurable and low enough not to damage anything or to force leaks open that are normally shut. The number is a test condition, not a prediction: translating it into the leakage a building actually experiences needs a further step, and the common divide-by-twenty rule is a rough correlation from field data rather than physics." }, { "question": "Does a tighter building need more ventilation?", "answer": "It needs ventilation that is DESIGNED rather than accidental, which is not quite the same claim. A leaky building is ventilated by its defects — at a rate set by the weather, mostly through the parts of the envelope nobody chose, and at its highest on the coldest, windiest days when it costs the most. Sealing it does not remove the need for fresh air; it removes the uncontrolled supply, and the fresh air then has to come from openings and fans that were specified. This is why airtightness targets appear in codes alongside ventilation requirements rather than instead of them, and why a retrofit that seals an old house without adding controlled ventilation reliably produces condensation and mould within a year or two. The phrase that captures it in the trade is *build tight, ventilate right* — and the second half is a requirement, not advice." } ], "related": [ "trickle-vent", "mvhr" ] }, { "slug": "earthing", "concept": "Earthing and grounding", "family": "services", "definition": "The arrangement that connects an installation's metalwork to the general mass of earth, so that a fault current has a path large enough to operate a protective device before anyone can be hurt.", "url": "https://craftquantities.com/glossary/earthing/", "names": [ { "market": "UK", "term": "earthing", "alsoCalled": [ "earth", "TN-S", "TN-C-S", "PME", "TT", "main protective bonding", "CPC" ], "exactness": "false-friend", "note": "The SYSTEM TYPE is named and matters: TN-C-S (PME) borrows the supply neutral as the earth, TT uses an electrode on site. Neither classification exists in American vocabulary." }, { "market": "AU", "term": "earthing", "alsoCalled": [ "MEN", "multiple earthed neutral", "earth stake", "equipotential bonding" ], "exactness": "false-friend", "note": "MEN is the standard Australian arrangement and is closest to British TN-C-S, but it is its own system with its own rules — the names are not interchangeable even where the wiring resembles it." }, { "market": "US", "term": "grounding", "alsoCalled": [ "ground", "bonding", "EGC", "GEC", "grounding electrode", "neutral" ], "exactness": "false-friend", "note": "GROUNDING and BONDING are separate defined terms doing separate jobs, and conflating them is the classic error: bonding carries fault current, grounding sets the reference to earth." }, { "market": "CA", "term": "grounding", "alsoCalled": [ "ground", "bonding", "bonding conductor", "grounding electrode" ], "exactness": "false-friend", "note": "As the United States with the Canadian code's own terminology, where BONDING CONDUCTOR is used where American practice says equipment grounding conductor." } ], "standards": [ { "market": "UK", "standard": "BS 7671 Chapter 54 / Section 411", "covers": "Earthing arrangements and protective conductors, and protection against electric shock by automatic disconnection of supply." }, { "market": "US", "standard": "NEC Article 250", "covers": "Grounding and bonding, including the distinction between the grounding electrode system and the equipment grounding conductor." } ], "calculators": [ { "slug": "grounding-conductor-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/grounding-conductor-sizing-calculator.json" }, { "slug": "ground-rod-resistance-calculator", "json": "https://craftquantities.com/api/v1/calculators/ground-rod-resistance-calculator.json" }, { "slug": "grounding-grid-resistance-calculator", "json": "https://craftquantities.com/api/v1/calculators/grounding-grid-resistance-calculator.json" }, { "slug": "lightning-rod-protection-calculator", "json": "https://craftquantities.com/api/v1/calculators/lightning-rod-protection-calculator.json" } ], "confusions": [ { "question": "What is the difference between grounding and bonding?", "answer": "They do different jobs, and the American code separates them because confusing the two produces installations that look safe and are not. BONDING connects metal parts together so that during a fault they are all at the same potential and a large current can flow back to the source, which is what makes a breaker trip. GROUNDING connects the system to the earth itself, which sets a reference potential and gives lightning and high-voltage surges somewhere to go. The crucial point is that the EARTH IS A POOR CONDUCTOR: the resistance of a ground rod is typically tens of ohms, which at mains voltage passes a few amps — nowhere near enough to trip anything. So the earth does not clear faults; the bonded metallic path back to the transformer does. Anyone who believes a ground rod protects them from a short circuit has the mechanism exactly backwards, and that belief is the reason the two words are defined separately." }, { "question": "Why does the British system have letter codes and the American one does not?", "answer": "Because in Britain the source of the earth varies, and what you are allowed to install depends on which one you have. TN-S gives a separate earth conductor all the way from the supply transformer. TN-C-S, usually called PME, combines neutral and earth in the supply and separates them at the cut-out, which gives a very low earth resistance and, in exchange, a specific hazard if that combined conductor breaks. TT has no earth from the supply at all and relies on an electrode at the property, which means fault currents are far too small for a fuse and residual current protection becomes mandatory rather than optional. So the letters are a design input: they determine acceptable disconnection times, whether an RCD is required, and whether bonding an outbuilding or an electric vehicle charge point is safe. American practice standardises the supply arrangement instead, so the classification has nothing to vary over." }, { "question": "Why must an EV charge point be treated specially on a PME supply?", "answer": "Because PME's specific failure mode meets an appliance held by a person standing on the ground. In a TN-C-S system the earth is derived from the supply's combined neutral-and-earth conductor, so if that conductor breaks somewhere upstream, every earthed metal part in the property can rise towards mains potential — and indoors that is tolerable because everything around is bonded to the same rising potential, so there is no difference for current to cross. Outdoors it is not: a person on real earth touching a car that is now at a raised potential bridges the difference. British wiring rules therefore require an EV installation on a PME supply either to have its own earth electrode or to use equipment that detects the voltage rise and disconnects. It is a good illustration of why the system classification is worth naming at all: the wiring in the house is unchanged, and the correct installation outside it is different." } ], "related": [ "rcd" ] }, { "slug": "fire-door", "concept": "Fire door", "family": "envelope", "definition": "A door assembly tested to hold back fire and smoke for a stated period. The rating belongs to the whole assembly — leaf, frame, seals, hinges and closer — not to the leaf alone.", "url": "https://craftquantities.com/glossary/fire-door/", "names": [ { "market": "UK", "term": "fire door", "alsoCalled": [ "FD30", "FD60", "FD30S", "notional fire door", "fire resisting doorset" ], "exactness": "false-friend", "note": "The number is MINUTES OF INTEGRITY and the trailing S means smoke seals. A door marked FD30 without the S is not a smoke door, which is the distinction most often missed in a corridor." }, { "market": "AU", "term": "fire door", "alsoCalled": [ "FRL", "-/60/30", "fire door set", "tagged door", "smoke door" ], "exactness": "false-friend", "note": "FRL is THREE figures — structural adequacy / integrity / insulation — so a single number cannot express an Australian rating. A dash means that criterion is not required." }, { "market": "US", "term": "fire door", "alsoCalled": [ "20-minute door", "90-minute door", "labeled door", "fire door assembly", "positive pressure" ], "exactness": "false-friend", "note": "The rating is tied to the WALL the door sits in and to a listing label, and positive-pressure testing changed which assemblies qualify — so an unlabelled door has no rating regardless of construction." }, { "market": "CA", "term": "fire door", "alsoCalled": [ "labelled door", "fire protection rating", "ULC label", "closure" ], "exactness": "close", "note": "CLOSURE is the code's own word covering doors, shutters and dampers together, and the rating is a FIRE PROTECTION rating, distinguished from the fire RESISTANCE rating of the wall." } ], "standards": [ { "market": "UK", "standard": "BS 476-22 / BS EN 1634-1", "covers": "Fire resistance tests for non-loadbearing elements including doorsets, and the European test method that increasingly replaces it." }, { "market": "US", "standard": "NFPA 80 / UL 10C", "covers": "Fire doors and other opening protectives including installation and inspection, and the positive pressure fire test for door assemblies." } ], "calculators": [ { "slug": "fire-rated-gypsum-layer-calculator", "json": "https://craftquantities.com/api/v1/calculators/fire-rated-gypsum-layer-calculator.json" }, { "slug": "fire-rated-glazing-clearance-lookup", "json": "https://craftquantities.com/api/v1/calculators/fire-rated-glazing-clearance-lookup.json" }, { "slug": "door-maneuvering-clearance-calculator", "json": "https://craftquantities.com/api/v1/calculators/door-maneuvering-clearance-calculator.json" } ], "confusions": [ { "question": "Does a fire door rating apply to the door or to the whole assembly?", "answer": "The assembly, and that is the single most consequential fact about them. What was tested was a complete doorset: a leaf of a particular construction, in a frame of a particular material, hung on particular hinges, with particular intumescent seals in particular grooves, closing with a particular device, in a wall of a particular type. Change any of those and the evidence no longer covers the installation. In practice that means the rating is lost by ordinary-looking decisions — fitting a letterplate, replacing broken hinges with whatever is in the van, planing the leaf to cure a sticking door, filling the gap between frame and structure with ordinary foam, or hanging a rated leaf in an unrated frame. Each looks like maintenance and each is a modification to a tested assembly. It is also why a fire door is inspected as an assembly, and why the gap around the leaf is measured rather than eyeballed." }, { "question": "What do the numbers in an Australian FRL mean, and why are there three?", "answer": "They are three different failure modes, tested together and reported separately, because an element can fail one and pass the others. STRUCTURAL ADEQUACY is how long it keeps carrying its load — irrelevant for most doors, which is why the first figure is usually a dash. INTEGRITY is how long it stops flames and hot gases passing through, which is what a British FD number reports. INSULATION is how long the unexposed face stays cool enough not to ignite what is against it, and this is the one a single-number system does not tell you. A door can hold flame back for an hour while its own back face becomes hot enough to set light to a coat hanging on it, so a door rated -/60/30 is honest about lasting an hour against flame and half an hour before the far side becomes dangerous. Anyone reading an Australian specification with British habits will read the middle number and lose the third." }, { "question": "Why does the gap around a fire door matter so much?", "answer": "Because the seals that close it only work over the range they were tested across. Intumescent strips swell when they get hot and fill the gap, and that expansion is finite: a gap of a few millimetres closes, a gap of twelve does not, and hot gas passes straight through a door whose leaf is intact. So the permitted gap is specified tightly at the head and stiles, and a larger one at the threshold is allowed only where the design accounts for it. The two failures this produces are opposite and equally common: a door planed to stop it binding, which opens the gap past what the seals can bridge; and a door fitted so tightly that the closer cannot latch it, so it sits ajar and has no rating at all because an unlatched fire door is an opening. That is also why the closer and the latch are part of the rated assembly rather than convenience hardware — a door that does not fully close and latch is not a fire door in any market." } ], "related": [ "firestopping" ] }, { "slug": "sustainable-drainage", "concept": "Sustainable drainage", "family": "site", "definition": "Managing rainfall close to where it lands — by soaking it away, holding it back or slowing it down — rather than collecting it into a pipe and discharging it downstream as fast as possible.", "url": "https://craftquantities.com/glossary/sustainable-drainage/", "names": [ { "market": "UK", "term": "SuDS", "alsoCalled": [ "sustainable drainage systems", "attenuation", "greenfield runoff rate", "swale", "soakaway" ], "exactness": "false-friend", "note": "ATTENUATION means holding water back to limit the DISCHARGE RATE, which is a separate requirement from limiting the total volume. Both are commonly imposed and they are met by different things." }, { "market": "AU", "term": "WSUD", "alsoCalled": [ "water sensitive urban design", "raingarden", "bioretention", "OSD", "on-site detention" ], "exactness": "close", "note": "WSUD is broader than drainage alone, taking in water supply and reuse. ON-SITE DETENTION is the narrower requirement most often written into an approval condition." }, { "market": "US", "term": "LID", "alsoCalled": [ "low impact development", "BMP", "best management practice", "green infrastructure", "bioswale" ], "exactness": "false-friend", "note": "BMP names an individual PRACTICE chosen from an approved list, and in older usage often meant a water-QUALITY treatment device. It is not a synonym for the design approach LID describes." }, { "market": "CA", "term": "LID", "alsoCalled": [ "low impact development", "stormwater BMP", "green infrastructure", "bioretention" ], "exactness": "close", "note": "As the United States, with frost depth a live design constraint that the American guidance for warmer states does not address — an infiltration bed that freezes does not infiltrate." } ], "standards": [ { "market": "UK", "standard": "CIRIA C753 / BS 8582", "covers": "The SuDS Manual, and the code of practice for surface water management for development sites including discharge rate limits." }, { "market": "US", "standard": "EPA NPDES stormwater / ASCE 45", "covers": "Permitting requirements for stormwater discharges, and the standard guidelines for the design of urban subsurface drainage." } ], "calculators": [ { "slug": "rational-method-peak-runoff-calculator", "json": "https://craftquantities.com/api/v1/calculators/rational-method-peak-runoff-calculator.json" }, { "slug": "picp-infiltration-storage-calculator", "json": "https://craftquantities.com/api/v1/calculators/picp-infiltration-storage-calculator.json" }, { "slug": "permeable-joint-fill-stone-calculator", "json": "https://craftquantities.com/api/v1/calculators/permeable-joint-fill-stone-calculator.json" }, { "slug": "silt-fence-run-calculator", "json": "https://craftquantities.com/api/v1/calculators/silt-fence-run-calculator.json" }, { "slug": "sediment-basin-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/sediment-basin-sizing-calculator.json" }, { "slug": "erosion-control-blanket-calculator", "json": "https://craftquantities.com/api/v1/calculators/erosion-control-blanket-calculator.json" } ], "confusions": [ { "question": "What is the difference between attenuation and infiltration?", "answer": "Where the water ends up, and they satisfy different requirements. INFILTRATION puts the water into the ground, so it leaves the drainage system entirely — a soakaway, a permeable pavement over free-draining ground, an infiltration basin. ATTENUATION holds the water temporarily and releases it slowly into a sewer or watercourse, so the same volume still leaves, just not all at once — a tank, a pond, an oversized pipe with a flow control. The distinction matters because approvals usually impose two separate limits: a peak DISCHARGE RATE, often pegged to what the site would have shed before it was built on, and sometimes a total VOLUME. Attenuation meets a rate limit and does nothing for a volume limit; infiltration meets both but only works if the ground will actually take water. That is why the infiltration test comes before the design rather than after it: on clay the answer is attenuation whatever the planning statement aspires to." }, { "question": "Why is a percolation test done in a pit rather than a borehole?", "answer": "Because the number wanted is how fast the ground will accept water from a full soakaway, not how permeable a sample is. The British method digs a trial pit of realistic dimensions, fills it, lets it drain, and measures the time to fall between set fractions of the effective depth — repeated three times, with the SLOWEST result used, because the first fill runs into dry ground and flatters the answer. Doing it in a narrow borehole changes the ratio of wetted side area to stored volume, which is exactly the geometry the result depends on. Two further conditions decide whether the design is honest: the test must reach the depth the soakaway will sit at, since a permeable topsoil over clay gives a fine result and a useless soakaway; and it should not be done after a dry spell, when shrinkage cracks in clay let water away at a rate that closes up as soon as the ground swells." }, { "question": "Is permeable paving a drainage system or a surface?", "answer": "Both, and treating it as a surface is how it fails. The blocks or the porous asphalt only get water through the top; the working part is the sub-base beneath, which is an open-graded stone with a large void ratio acting as a tank, plus whatever outlet the design gives it — infiltration into the ground, a controlled pipe, or both. So the design questions are the storage volume in that stone, the rate the ground beneath will accept, and what happens in the storm that exceeds both. The failures follow from ignoring the layer that matters: laying it over a compacted clay formation that cannot infiltrate, bedding it on ordinary sand which migrates into the voids and fills them, allowing silt-laden runoff from an adjacent area onto it so the joints clog, or never sweeping it. A permeable pavement is a piece of drainage infrastructure with a maintenance regime, and the one that gets neither is impermeable within a few years." } ], "related": [ "soakaway" ] }, { "slug": "sealant", "concept": "Sealant and caulk", "family": "finishes", "definition": "A flexible material gunned into a joint to keep water and air out while allowing the two sides to move relative to each other. Its performance is a property of the JOINT, not only of the material.", "url": "https://craftquantities.com/glossary/sealant/", "names": [ { "market": "UK", "term": "mastic", "alsoCalled": [ "sealant", "silicone", "caulk", "decorator's caulk", "frame sealant" ], "exactness": "false-friend", "note": "DECORATOR'S CAULK is a paintable acrylic filler for static internal gaps and is not a weather sealant. Calling both caulk hides a difference that decides whether a joint survives outdoors." }, { "market": "AU", "term": "sealant", "alsoCalled": [ "silicone", "gap filler", "mastic", "polyurethane sealant" ], "exactness": "close", "note": "GAP FILLER is the retail name for the paintable acrylic, the same product British usage calls decorator's caulk, and it carries the same limitation on movement and exposure." }, { "market": "US", "term": "caulk", "alsoCalled": [ "sealant", "silicone", "mastic", "backer rod", "glazing sealant" ], "exactness": "false-friend", "note": "MASTIC usually means a trowel-applied ADHESIVE — tile mastic, duct mastic — so a British instruction to run mastic round a frame reads as an instruction to use glue." }, { "market": "CA", "term": "caulk", "alsoCalled": [ "caulking", "sealant", "backer rod", "acoustical sealant" ], "exactness": "close", "note": "As the United States, with ACOUSTICAL SEALANT named as a distinct product because it must stay permanently soft rather than cure hard, which is the opposite requirement to a weather seal." } ], "standards": [ { "market": "UK", "standard": "BS EN ISO 11600 / BS 6213", "covers": "Classification and requirements for sealants by movement capability, and the guide to the selection of construction sealants." }, { "market": "US", "standard": "ASTM C920 / ASTM C1193", "covers": "Elastomeric joint sealants classified by movement class, and the standard guide for use of joint sealants including joint design." } ], "calculators": [ { "slug": "caulk-sealant-calculator", "json": "https://craftquantities.com/api/v1/calculators/caulk-sealant-calculator.json" }, { "slug": "fiber-cement-caulk-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/fiber-cement-caulk-volume-calculator.json" }, { "slug": "acoustic-sealant-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/acoustic-sealant-volume-calculator.json" } ], "confusions": [ { "question": "Why does a sealant joint need a backer rod?", "answer": "To control the DEPTH, and to stop the sealant sticking to the back of the joint. A sealant bead stretches when the joint opens, and how far it can stretch depends on its shape: a bead that is shallow relative to its width distributes the movement across a thin section and survives it, while a deep plug of sealant concentrates strain at the edges and tears away from one side. The usual design target is a depth of about half the width, within a stated minimum and maximum, and a closed-cell foam rod pressed into the joint sets that depth in one operation. It also creates the second condition: the sealant must bond to TWO sides only. If it also adheres to the back of the joint — three-sided adhesion — it cannot deform freely, and it splits down the middle or peels off a face the first time the joint moves properly. Where there is no room for a rod, bond-breaker tape does the same job." }, { "question": "What does a movement class actually promise?", "answer": "The percentage of the joint's own width the sealant can take, repeatedly, without failing — and it is a percentage, which is why joint width is a design decision rather than whatever gap turns up. A sealant classified at twenty-five percent in a ten-millimetre joint accommodates two and a half millimetres of movement; the same product in a twenty-millimetre joint accommodates five. So the joint is sized from the movement expected, which comes from the panel length, the material's thermal expansion, and the temperature range it will see between the coldest night and a dark surface in summer sun. The classification also distinguishes extension from compression, which are not symmetrical — most sealants take compression better than extension. This is the reason a joint that failed is rarely fixed by a better sealant: if the gap is too narrow for the movement, every product in it will be over-extended." }, { "question": "Why does silicone fail on some surfaces and not others?", "answer": "Because adhesion is chemistry plus preparation, and silicone is the least forgiving common sealant about both. It will not bond reliably to damp substrates, to dusty or chalking surfaces, to some plastics without a primer, or to anything still carrying a release agent or a mould oil — and on porous materials such as natural stone the oils in some formulations migrate into the surface and leave a permanent dark halo either side of the joint, which is why low-modulus neutral-cure grades are specified there. It also cannot be painted, so it must be the final finish rather than a stage in one. Against that, nothing beats it for permanent flexibility and weathering. The practical consequence is that the product is chosen from the SUBSTRATES and the movement together — polyurethane where the joint will be painted or trafficked, acrylic only where there is no movement and no weather, silicone where flexibility and water matter most — and every one of them fails on a surface that was not cleaned." } ], "related": [ "movement-joint" ] }, { "slug": "tolerance", "concept": "Tolerance and permitted deviation", "family": "measurement", "definition": "How far the built work may depart from the drawing and still be accepted. Stated as a permitted deviation over a stated length, because the same error means different things at different scales.", "url": "https://craftquantities.com/glossary/tolerance/", "names": [ { "market": "UK", "term": "tolerance", "alsoCalled": [ "permissible deviation", "out of plumb", "out of level", "SR1", "surface regularity" ], "exactness": "false-friend", "note": "SURFACE REGULARITY classes SR1 to SR3 grade a floor by the gap under a two-metre straightedge. It measures FLATNESS over a short span and says nothing about whether the floor is level." }, { "market": "AU", "term": "tolerance", "alsoCalled": [ "permissible deviation", "out of square", "straightness", "guide to standards" ], "exactness": "close", "note": "Residential disputes are commonly argued against a published guide to standards and tolerances rather than a design standard, so the acceptance figure and the design figure can differ." }, { "market": "US", "term": "tolerance", "alsoCalled": [ "FF", "FL", "F-number", "floor flatness", "floor levelness", "out of plumb" ], "exactness": "false-friend", "note": "F-NUMBERS are two separate statistical measures — FF for flatness, FL for levelness — computed from a survey. Neither is a straightedge gap, and neither converts to an SR class." }, { "market": "CA", "term": "tolerance", "alsoCalled": [ "FF", "FL", "F-number", "permissible variation" ], "exactness": "close", "note": "As the United States, with F-numbers standard on commercial slabs and a straightedge check still common on smaller residential work." } ], "standards": [ { "market": "UK", "standard": "BS 5606 / BS 8204-1", "covers": "Guide to accuracy in building, and screeds and in-situ floorings including the SR surface regularity classes." }, { "market": "US", "standard": "ACI 117 / ASTM E1155", "covers": "Specification for tolerances for concrete construction and materials, and determining floor flatness and levelness using the F-number system." } ], "calculators": [ { "slug": "riser-spread-tolerance-checker", "json": "https://craftquantities.com/api/v1/calculators/riser-spread-tolerance-checker.json" }, { "slug": "rectangle-diagonal-squaring-calculator", "json": "https://craftquantities.com/api/v1/calculators/rectangle-diagonal-squaring-calculator.json" }, { "slug": "self-leveling-underlayment-calculator", "json": "https://craftquantities.com/api/v1/calculators/self-leveling-underlayment-calculator.json" } ], "confusions": [ { "question": "What is the difference between flat and level?", "answer": "FLAT is about the surface's own local smoothness; LEVEL is about its relationship to horizontal. A floor that falls two centimetres across a room but has no bumps in it is perfectly flat and badly out of level. A floor that is dead horizontal on average but ripples every metre is level and not flat. They matter to different things: flatness decides whether a tile lippage appears, whether a long piece of furniture rocks, whether a forklift jolts; levelness decides whether doors swing open on their own, whether water runs to the drain, whether a run of units meets a worktop straight. This is why the American system quotes two numbers and the British straightedge check quotes one — a two-metre straightedge measures flatness only, and a floor can pass SR1 while sloping steadily. Anyone specifying a floor by surface regularity alone has said nothing about level, and that omission is a common source of dispute." }, { "question": "Why is a tolerance quoted over a length?", "answer": "Because deviation without a gauge length is meaningless, and the same absolute error is trivial at one scale and unacceptable at another. Three millimetres out of plumb is invisible over a storey height and severe over a door frame; a five-millimetre dip is nothing across a room and a defect under a two-metre straightedge. So every honest tolerance names both numbers — so many millimetres in so many metres, or a gap under a straightedge of a stated length — and comparing two specifications means comparing both. It also explains why tolerances do not add up the way intuition suggests: a wall built to a permitted deviation per storey does not accumulate that deviation over four storeys, because each is measured from the reference rather than from the one below. Where they DO accumulate is the thing to watch — a series of components each cut to its own tolerance can leave a final gap far outside any of them, which is why setting out works from a datum and not from the last thing fixed." }, { "question": "Whose tolerance governs when two trades meet?", "answer": "Neither, unless somebody wrote down the junction — and that gap is where most tolerance arguments live. Each trade works to a standard that is reasonable on its own: a concrete frame has a permitted deviation, a window has a manufacturing tolerance, a cladding panel has another, and every one of them may be within limits while the joint between them is impossible. The frame leans a permitted amount, the opening is a permitted amount out of square, and the panel that must cover both is made to a tighter tolerance than either. The answer used on well-run jobs is to design the JOINT to absorb the sum: a cover bead wide enough for the worst combination, a shim gap, an adjustable bracket. That is also why surveying the structure before ordering the components is standard on facades — the tolerance is not the problem, discovering it after manufacture is." } ], "related": [ "nominal-size" ] }, { "slug": "thermal-bridge", "concept": "Thermal bridge", "family": "envelope", "definition": "A path through the envelope that conducts heat faster than the surfaces around it — usually where two elements meet, or where a structural member interrupts the insulation.", "url": "https://craftquantities.com/glossary/thermal-bridge/", "names": [ { "market": "UK", "term": "thermal bridge", "alsoCalled": [ "cold bridge", "psi value", "y-value", "junction detail", "accredited construction details" ], "exactness": "false-friend", "note": "PSI VALUE is a linear transmittance in W/m·K for a specific junction, summed over its length. It is a separate quantity from the U-value of the surfaces, added to them rather than included." }, { "market": "AU", "term": "thermal bridge", "alsoCalled": [ "thermal bridging", "steel framing correction", "total R-value" ], "exactness": "close", "note": "Addressed mainly through a correction applied to a framed wall's total R-value rather than a per-junction figure, so the arithmetic differs even where the concept matches." }, { "market": "US", "term": "thermal bridging", "alsoCalled": [ "continuous insulation", "ci", "framing factor", "parallel path", "clear field" ], "exactness": "false-friend", "note": "Usually handled by REQUIRING continuous insulation of a stated R-value rather than by calculating the bridge. CI is a prescription; a psi value is a measurement." }, { "market": "CA", "term": "thermal bridging", "alsoCalled": [ "continuous insulation", "effective R-value", "linear transmittance", "point transmittance" ], "exactness": "close", "note": "EFFECTIVE R-VALUE is the assembly figure after bridging is deducted, and Canadian practice publishes catalogues of linear and point transmittances closer to the British approach." } ], "standards": [ { "market": "UK", "standard": "BR 497 / BRE IP 1/06", "covers": "Conventions for calculating linear thermal transmittance and temperature factors, and assessing the effects of thermal bridging at junctions." }, { "market": "US", "standard": "ASHRAE 90.1 / ASHRAE 1365-RP", "covers": "Energy standard requirements including continuous insulation, and the research report giving linear and point transmittances for building envelope details." } ], "calculators": [ { "slug": "thermal-bridging-calculator", "json": "https://craftquantities.com/api/v1/calculators/thermal-bridging-calculator.json" }, { "slug": "ci-thermal-bridging-calculator", "json": "https://craftquantities.com/api/v1/calculators/ci-thermal-bridging-calculator.json" }, { "slug": "window-wall-u-factor-calculator", "json": "https://craftquantities.com/api/v1/calculators/window-wall-u-factor-calculator.json" } ], "confusions": [ { "question": "Is a thermal bridge included in a wall's U-value?", "answer": "The repeating ones are; the junctions are not, and that is the distinction that gets lost. A U-value is calculated for a REPEATING assembly, so bridges that recur at a regular spacing through it — the studs in a timber wall, the mortar joints in blockwork, the ties across a cavity — are already averaged into the figure. What is not in it is every place the assembly STOPS: where the wall meets the floor, the roof, a window reveal, a lintel, a balcony, a party wall. Those are one-off geometries, they are where insulation is most often interrupted, and in a well-insulated building they can account for a substantial share of the total fabric heat loss. British method adds them explicitly as a sum of psi-values times lengths. Anyone reading a U-value as the whole story is reading the easy part of the envelope and ignoring the part the site actually gets wrong." }, { "question": "Why do thermal bridges matter more as insulation improves?", "answer": "Because the bridge does not improve with it, so its SHARE of the loss grows. Insulating a wall better reduces the heat going through the field of the wall, but the junction where the insulation is interrupted conducts at much the same rate it always did — its geometry has not changed. A poorly insulated building loses heat everywhere and the junctions are a rounding error; a well-insulated one loses heat mostly at the places the insulation stops. The consequence is that upgrading insulation without improving the junctions gives less than the arithmetic promises, and the gap widens the better the insulation gets. It is also why detailing takes over from specification as the envelope improves: choosing a thicker board is a purchase, and making the insulation line continuous around a lintel is a drawing and a site instruction." }, { "question": "What is the temperature factor, and why is it not about energy?", "answer": "It is about MOULD, and it is the reason a thermal bridge can be a health problem rather than a bill. The temperature factor compares the temperature of the internal surface at the bridge against the difference between inside and outside, giving a number that says how cold that surface gets relative to the room. Energy loss is proportional to area and a small junction loses little, but the SURFACE there can be cold enough for the air against it to reach its dew point — and a surface that spends winter above roughly eighty percent relative humidity grows mould, well before it is cold enough to show condensation running down it. That is why guidance sets a minimum temperature factor for junctions independently of any energy target, why mould in a corner or behind a wardrobe on an external wall is a detailing symptom rather than a housekeeping one, and why a bridge that costs almost nothing in heat can still fail." } ], "related": [ "r-value" ] }, { "slug": "roof-truss", "concept": "Roof truss and cut roof", "family": "structure", "definition": "A prefabricated triangulated frame carrying a roof, designed as a unit and delivered complete — as opposed to a roof assembled on site from individual rafters, purlins and struts.", "url": "https://craftquantities.com/glossary/roof-truss/", "names": [ { "market": "UK", "term": "trussed rafter", "alsoCalled": [ "roof truss", "fink truss", "cut roof", "traditional roof", "gang-nail" ], "exactness": "false-friend", "note": "A CUT ROOF is the site-assembled alternative and is a different thing entirely — different members, different span rules, and alterable where a trussed rafter is not." }, { "market": "AU", "term": "roof truss", "alsoCalled": [ "trussed rafter", "nail plate", "conventional roof", "pitched roof framing" ], "exactness": "close", "note": "CONVENTIONAL ROOF is the site-cut alternative, and wind classification drives the tie-down detail far more explicitly than in British practice." }, { "market": "US", "term": "truss", "alsoCalled": [ "roof truss", "stick-built", "rafter framing", "gusset plate", "truss uplift" ], "exactness": "false-friend", "note": "STICK-BUILT is the site-cut alternative. TRUSS UPLIFT names a specific seasonal movement of the bottom chord that cracks ceilings and is not a defect." }, { "market": "CA", "term": "truss", "alsoCalled": [ "roof truss", "stick framing", "truss uplift", "heel height" ], "exactness": "close", "note": "As the United States, with HEEL HEIGHT — the depth at the wall plate — a routine specification because it decides whether full insulation depth fits over the wall." } ], "standards": [ { "market": "UK", "standard": "BS EN 14250 / BS 5268-3 legacy", "covers": "Prefabricated structural members assembled with punched metal plate fasteners, and the historic code of practice for trussed rafter roofs." }, { "market": "US", "standard": "ANSI/TPI 1 / BCSI", "covers": "National design standard for metal plate connected wood truss construction, and the guide to good practice for handling, installing, restraining and bracing them." } ], "calculators": [ { "slug": "roof-truss-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-truss-spacing-calculator.json" }, { "slug": "truss-camber-calculator", "json": "https://craftquantities.com/api/v1/calculators/truss-camber-calculator.json" }, { "slug": "truss-bottom-chord-deflection-calculator", "json": "https://craftquantities.com/api/v1/calculators/truss-bottom-chord-deflection-calculator.json" }, { "slug": "truss-plate-connector-calculator", "json": "https://craftquantities.com/api/v1/calculators/truss-plate-connector-calculator.json" } ], "confusions": [ { "question": "Why can a truss never be cut?", "answer": "Because every member in it is carrying a calculated force, and there is no redundancy to absorb the loss of one. A truss is not a beam with decoration: it is a triangulated frame in which the top chords are in compression, the bottom chord is in tension along its whole length, and each web transfers force between them at a designed angle. Cut a web to get a water tank through, notch a bottom chord for a pipe, or trim a top chord for a rooflight, and the forces that member was carrying have nowhere to go — the frame deflects, the plates at the joints start to withdraw, and the failure is of the whole truss rather than of the piece that was cut. The bottom chord is the worst case, because a member in tension has no reserve at all and is often mistaken for a ceiling joist that happens to be there. Any alteration needs a design, which in practice means new trusses or a steel to carry the ones removed." }, { "question": "What is truss uplift, and is the ceiling cracking a defect?", "answer": "It is seasonal movement, and the crack is real while the truss is fine. In a cold climate the bottom chord of a truss sits buried in loft insulation and stays at room-ish humidity, while the top chords are in the cold, dry loft air above it. Over winter the top chords lose moisture and shrink slightly, which bows the whole truss upward in the middle and lifts the bottom chord — and the ceiling fixed to it — away from the internal partition walls, which do not move. A gap opens along the top of the partition, typically a few millimetres, and closes again in summer. Nothing is overloaded and nothing is failing. The cure is detailing rather than structure: fix the ceiling boards to clips that allow the movement rather than to the partition head, and cover the junction with a coving fixed to the CEILING only, so the gap opens behind it where it cannot be seen." }, { "question": "When is a cut roof still the right answer?", "answer": "When the shape is complicated, when the loft is to be used, or when the roof cannot be craned. Trussed rafters are cheaper and faster over a simple rectangular plan because the design and the cutting happen in a factory, but they fill the roof space with webs and they arrive as large, fragile assemblies that need access and lifting. A cut roof is assembled from members a person can carry up a ladder, so it suits a restricted site, a small extension or a repair; it can follow a complicated plan with hips, valleys and dormers without a bespoke truss for every position; and with a purlin and struts carried down to loadbearing walls it leaves the middle of the roof space open, which is what makes a room in the roof possible. Attic trusses exist to bridge that last gap, and they cost and weigh substantially more than a standard one." } ], "related": [ "purlin" ] }, { "slug": "double-glazing", "concept": "Insulating glazing unit", "family": "envelope", "definition": "Two or more panes sealed around a spacer with a gas-filled gap between them. The gap does the insulating; the panes mostly carry the coatings that decide how much solar heat and light get through.", "url": "https://craftquantities.com/glossary/double-glazing/", "names": [ { "market": "UK", "term": "double glazing", "alsoCalled": [ "sealed unit", "IGU", "g-value", "warm edge spacer", "low-E", "argon filled" ], "exactness": "false-friend", "note": "G-VALUE is the solar transmittance, quoted 0 to 1 and measured to a European method. It is close to but not identical with the American SHGC, and the two are not interchangeable in a calculation." }, { "market": "AU", "term": "double glazing", "alsoCalled": [ "IGU", "SHGC", "insulated glass unit", "toned glass", "WERS rating" ], "exactness": "close", "note": "Uses SHGC rather than g-value, and solar control usually matters more than the U-value — the reverse of the British priority, which is why an imported specification often optimises the wrong number." }, { "market": "US", "term": "insulated glass unit", "alsoCalled": [ "IGU", "double pane", "thermal pane", "SHGC", "U-factor", "low-E", "NFRC label" ], "exactness": "false-friend", "note": "SHGC to the NFRC method, alongside a U-FACTOR that is not the British U-value either — different reference conditions and, historically, different units." }, { "market": "CA", "term": "insulated glass unit", "alsoCalled": [ "IGU", "sealed unit", "ER rating", "energy rating", "SHGC" ], "exactness": "false-friend", "note": "The ENERGY RATING combines U-factor, solar gain and air leakage into one number that can be NEGATIVE, so it cannot be compared with any single-property figure at all." } ], "standards": [ { "market": "UK", "standard": "BS EN 1279 / BS EN 410", "covers": "Insulating glass units including durability of the edge seal, and determination of luminous and solar characteristics of glazing." }, { "market": "US", "standard": "NFRC 100 / NFRC 200 / ASTM E2190", "covers": "Procedures for determining fenestration U-factors and solar heat gain coefficient, and insulating glass unit performance evaluation." } ], "calculators": [ { "slug": "shgc-effective-shading-calculator", "json": "https://craftquantities.com/api/v1/calculators/shgc-effective-shading-calculator.json" }, { "slug": "window-heat-loss-savings-calculator", "json": "https://craftquantities.com/api/v1/calculators/window-heat-loss-savings-calculator.json" }, { "slug": "glazing-gasket-linear-footage-calculator", "json": "https://craftquantities.com/api/v1/calculators/glazing-gasket-linear-footage-calculator.json" }, { "slug": "acoustic-glass-stc-estimator", "json": "https://craftquantities.com/api/v1/calculators/acoustic-glass-stc-estimator.json" }, { "slug": "glass-panel-weight-calculator", "json": "https://craftquantities.com/api/v1/calculators/glass-panel-weight-calculator.json" }, { "slug": "blast-glazing-rating-checker", "json": "https://craftquantities.com/api/v1/calculators/blast-glazing-rating-checker.json" } ], "confusions": [ { "question": "Is a g-value the same as an SHGC?", "answer": "Close enough to be confusing and not close enough to substitute. Both express the fraction of incident solar energy that ends up inside — direct transmission plus the share of what the glass absorbs and then re-radiates inward — on a scale from zero to one. They differ in the reference conditions the test uses, and, more importantly in practice, in what the number is attached to: a g-value is usually quoted for the GLASS, while an NFRC SHGC is usually quoted for the whole WINDOW including the frame, which lowers it because the frame transmits no sunlight. So taking a glass g-value from a European datasheet and entering it as a whole-window SHGC overstates the solar gain, and doing the reverse understates it. The rule that avoids both is to establish whether a figure describes the glass or the assembly before using it, in either direction." }, { "question": "Why does the gas in the gap matter, and does it leak out?", "answer": "It matters because the gap conducts and convects, and argon does both less well than air — the same reason the gap has an optimum width rather than being as wide as possible. Too narrow and the panes conduct across it; too wide and the gas circulates, carrying heat from the warm pane to the cold one, so performance stops improving and then gets worse. Argon's lower conductivity and higher viscosity move that optimum and improve the figure by a useful margin for almost no cost. It does leak, slowly, through the edge seal — a small percentage a year is normal, and the unit's insulation degrades gradually rather than failing. The failure people actually see is different: the desiccant in the spacer saturates, moisture gets in, and the unit MISTS internally. That is an edge-seal failure, it cannot be cleaned, and it is why the durability standard for units is about the seal rather than about the glass." }, { "question": "Why is the spacer called a warm edge, and does it change the rating?", "answer": "Because a traditional aluminium spacer is a thermal bridge running around the entire perimeter of every unit, and the edge is where condensation and mould appear first. Aluminium conducts hundreds of times better than the gas it is holding apart, so it short-circuits the gap at the edge: the glass there runs several degrees colder than the centre, and in a humid room that band is where water forms. A warm edge spacer is made of stainless steel, a structural foam or a composite — materials chosen to hold the panes apart while conducting as little as possible. It improves the whole-window U-value by a modest amount, which is the part that appears on the label, and it raises the edge surface TEMPERATURE by rather more, which is the part occupants notice. It is the same distinction the thermal bridge concept draws generally: a small energy saving and a large comfort and condensation difference." } ], "related": [ "cill" ] }, { "slug": "vapour-control-layer", "concept": "Vapour control layer", "family": "envelope", "definition": "A sheet or coating that limits how fast water vapour diffuses into a construction, placed so that vapour does not reach a surface cold enough to condense on.", "url": "https://craftquantities.com/glossary/vapour-control-layer/", "names": [ { "market": "UK", "term": "vapour control layer", "alsoCalled": [ "VCL", "vapour barrier", "vapour check", "breather membrane", "sd-value" ], "exactness": "false-friend", "note": "A BREATHER MEMBRANE is the opposite product for the opposite face — vapour-open and weather-resistant, on the cold side. Confusing the two reverses the assembly." }, { "market": "AU", "term": "vapour barrier", "alsoCalled": [ "vapour permeable membrane", "sarking", "pliable membrane", "vapour control membrane" ], "exactness": "false-friend", "note": "SARKING in Australian use is the pliable membrane under the roof covering, not the British timber boarding of the same name — and vapour-permeable and vapour-barrier grades look alike on a roll." }, { "market": "US", "term": "vapor retarder", "alsoCalled": [ "vapor barrier", "Class I retarder", "Class II", "Class III", "perm rating", "kraft facing" ], "exactness": "false-friend", "note": "RETARDER is deliberate, and the three CLASSES are graded by perm rating. A Class I is a true barrier and is prohibited in some assemblies where a Class III is required." }, { "market": "CA", "term": "vapour barrier", "alsoCalled": [ "air barrier", "poly", "6-mil poly", "vapour retarder", "perm rating" ], "exactness": "false-friend", "note": "POLY is near-universal in Canadian housing and doubles as the AIR barrier, so one sheet does two jobs that the British approach usually separates into two products." } ], "standards": [ { "market": "UK", "standard": "BS 5250 / BS EN ISO 13788", "covers": "Management of moisture in buildings, and internal surface temperature and interstitial condensation calculation methods." }, { "market": "US", "standard": "IRC R702.7 / ASTM E96", "covers": "Vapor retarder class requirements by climate zone, and the test methods for water vapor transmission of materials." } ], "calculators": [ { "slug": "vapor-barrier-calculator", "json": "https://craftquantities.com/api/v1/calculators/vapor-barrier-calculator.json" }, { "slug": "vapor-barrier-dewpoint-calculator", "json": "https://craftquantities.com/api/v1/calculators/vapor-barrier-dewpoint-calculator.json" }, { "slug": "curtain-wall-condensation-checker", "json": "https://craftquantities.com/api/v1/calculators/curtain-wall-condensation-checker.json" }, { "slug": "dew-point-calculator", "json": "https://craftquantities.com/api/v1/calculators/dew-point-calculator.json" } ], "confusions": [ { "question": "Which side does the vapour control layer go on?", "answer": "The warm side — and the reason is worth holding onto, because it is what tells you what to do when the warm side changes. Vapour moves from warm, humid air towards cold, dry air, so in a heated building in winter it pushes outward through the construction. Somewhere in that path is a plane cold enough for the air's dew point, and if vapour reaches it faster than the construction can dry, water accumulates inside the wall where nobody sees it until the timber rots. Putting the control layer on the warm side stops most of the vapour before it gets there. The corollary is the dangerous case: in a hot, humid climate with air conditioning, the warm side is OUTSIDE, and a layer installed on the inside face is now on the cold side, trapping moisture driven inward from the outside. That is why the American classes are assigned by climate zone rather than given as one rule, and why a detail copied across climates is a genuine hazard rather than a stylistic difference." }, { "question": "What does an sd-value or a perm rating actually say?", "answer": "Both express how much a material resists vapour diffusion, in opposite directions of counting. The SD-VALUE, used in Britain and Europe, is the thickness of still air that would resist diffusion as much as the material does — measured in metres, so a bigger number means more resistance, and a polythene sheet might be fifty metres while a breather membrane is a fraction of one. A PERM RATING counts the transmission instead, so a bigger number means MORE vapour passes: that is why an American Class I retarder is defined by a very LOW perm rating. The two scales are therefore inverted with respect to each other, which is a reliable way to specify the exact opposite of what was intended when a datasheet crosses markets. Neither number is useful alone: what matters is the ratio between the resistance on the warm side and the resistance on the cold side, because that is what decides whether a wall that gets wet can dry." }, { "question": "Why does a wall need to dry, and how does a barrier stop it?", "answer": "Because every construction gets wet — from a leak, from building moisture, from vapour that got past the control layer through a gap at a socket or a joist end — and the question is never whether moisture enters but whether it can leave. A construction dries by vapour diffusing outward through its cold side, which is why the layer there should be MORE open than the layer on the warm side. Put an impermeable layer on both faces and the wall cannot dry in either direction, so the first leak is permanent. This is the reasoning behind the general rule that vapour resistance should decrease from inside to outside, behind the American prohibition on a Class I retarder in assemblies that need inward drying, and behind the damage done by fitting an impermeable cement render or a vinyl wallcovering to an old solid wall that was relying on drying through that face. A perfectly installed barrier on one side is fine; two of them is a trap." } ], "related": [ "dpm" ] }, { "slug": "asbestos", "concept": "Asbestos-containing material", "family": "materials", "definition": "Material containing asbestos fibres, which are hazardous when released into the air. Almost everything about how it is handled follows from whether disturbing it will release fibres, not from the amount present.", "url": "https://craftquantities.com/glossary/asbestos/", "names": [ { "market": "UK", "term": "asbestos", "alsoCalled": [ "ACM", "licensable work", "non-licensed", "notifiable non-licensed", "duty to manage", "refurbishment and demolition survey" ], "exactness": "false-friend", "note": "Work is graded LICENSABLE, NOTIFIABLE NON-LICENSED or non-licensed by the task and material, not by a property of the material alone. The category decides who may legally do it." }, { "market": "AU", "term": "asbestos", "alsoCalled": [ "ACM", "friable", "non-friable", "asbestos register", "Class A licence", "Class B licence" ], "exactness": "close", "note": "Splits on FRIABLE against non-friable like the United States, with Class A licences covering friable work and Class B covering bonded material above a threshold area." }, { "market": "US", "term": "asbestos", "alsoCalled": [ "ACM", "friable", "Category I non-friable", "Category II", "RACM", "AHERA", "NESHAP" ], "exactness": "false-friend", "note": "FRIABLE means crumbling under hand pressure when dry, and the categories classify the MATERIAL. British law classifies the WORK instead, so the two systems do not map onto each other." }, { "market": "CA", "term": "asbestos", "alsoCalled": [ "ACM", "Type 1", "Type 2", "Type 3", "friable", "asbestos inventory" ], "exactness": "false-friend", "note": "TYPE 1, 2 and 3 grade the operation by expected fibre release, set provincially — a third scheme again, and the numbers carry no relationship to the American categories." } ], "standards": [ { "market": "UK", "standard": "Control of Asbestos Regulations 2012 / HSG264", "covers": "Duties including the duty to manage in non-domestic premises, and the surveying guide distinguishing management from refurbishment and demolition surveys." }, { "market": "US", "standard": "40 CFR 61 Subpart M (NESHAP) / 29 CFR 1926.1101", "covers": "National emission standard for asbestos including notification and work practices, and the OSHA construction standard with its four exposure classes." } ], "calculators": [ { "slug": "asbestos-negative-pressure-cfm-calculator", "json": "https://craftquantities.com/api/v1/calculators/asbestos-negative-pressure-cfm-calculator.json" }, { "slug": "air-changes-per-hour-calculator", "json": "https://craftquantities.com/api/v1/calculators/air-changes-per-hour-calculator.json" } ], "confusions": [ { "question": "What does friable mean, and why does it decide so much?", "answer": "It means the material can be crumbled, pulverised or reduced to powder by hand pressure when dry — and it decides almost everything because it predicts whether ordinary disturbance releases fibres. Sprayed coatings, pipe lagging and insulating board are friable: the fibres are loosely bound, so cutting, drilling or simply knocking them puts fibres into the air. Asbestos cement sheet, vinyl floor tiles and bitumen products are non-friable: the fibres are locked into a hard matrix, and the material is comparatively low-risk intact. The distinction is about the BINDING, not the percentage — a cement sheet containing more asbestos by weight than an insulating board can be the safer material to have in a building. It also explains the trap: a non-friable material becomes friable the moment somebody takes an angle grinder or a power saw to it, which is why the prohibition on power tools appears in every set of rules regardless of category." }, { "question": "Why is a survey before work a different thing from the one on file?", "answer": "Because they answer different questions, and using the wrong one is a routine and serious error. A MANAGEMENT survey locates the material a building's occupants could disturb in normal use, and deliberately does not open up the structure — it is the basis of the register that tells a maintenance engineer what not to drill into. A REFURBISHMENT AND DEMOLITION survey is intrusive: it goes into ceiling voids, behind linings, under floors and into ducts, precisely because that is where the work is about to go. A management survey is therefore silent about exactly the places refurbishment reaches, and its silence is not a finding of absence. Starting a strip-out on a management survey is one of the most common ways a job discovers asbestos with the tools already running, which is the worst possible moment: work stops, the area becomes a potential contamination incident, and the cost of that dwarfs the survey." }, { "question": "Is leaving it alone really safer than removing it?", "answer": "Often yes, and that is genuinely counterintuitive. Intact, undamaged, non-friable material in a place nobody disturbs releases essentially nothing; removing it is a disturbance by definition, and every removal creates an episode of elevated fibre release that has to be controlled with enclosures, negative pressure and clearance testing. So the default duty in British law is to MANAGE rather than to remove: record where it is, assess its condition, label it, tell anyone who might work near it, and inspect it periodically. Removal becomes the right answer when the material is damaged, is deteriorating, is somewhere it will inevitably be disturbed, or is in the way of the work. The practical implication for anyone estimating a refurbishment is that the asbestos line item is not a fixed property of the building — it depends on which materials the design actually reaches, which makes it one of the few costs that a design change can remove entirely." } ], "related": [ "skip", "lead-paint", "textured-coating" ] }, { "slug": "anchor", "concept": "Anchor and fixing", "family": "structure", "definition": "A device that transfers load from something being fixed into the material behind it. Its capacity is a property of the pair — the anchor and the base material — never of the anchor alone.", "url": "https://craftquantities.com/glossary/anchor/", "names": [ { "market": "UK", "term": "fixing", "alsoCalled": [ "anchor", "rawlplug", "wall plug", "resin anchor", "through bolt", "frame fixing" ], "exactness": "false-friend", "note": "RAWLPLUG is a trademark used generically for any wall plug. FIXING also means the ACT of fixing and the fixed item, so a bill line reading fixings can mean three different things." }, { "market": "AU", "term": "anchor", "alsoCalled": [ "fastener", "wall plug", "Dynabolt", "chemical anchor", "masonry anchor" ], "exactness": "false-friend", "note": "DYNABOLT is a second genericised trademark, used for sleeve anchors generally — so a specification naming it may or may not intend that specific product." }, { "market": "US", "term": "anchor", "alsoCalled": [ "fastener", "wall anchor", "wedge anchor", "adhesive anchor", "toggle", "molly bolt" ], "exactness": "false-friend", "note": "ANCHOR means the masonry or concrete fixing; FASTENER is the broader word covering screws and nails. British FIXING covers both, so it maps onto neither cleanly." }, { "market": "CA", "term": "anchor", "alsoCalled": [ "fastener", "wedge anchor", "adhesive anchor", "Tapcon", "concrete screw" ], "exactness": "false-friend", "note": "TAPCON is a third genericised trademark, standing in for concrete screws generally, and the brand's own sizes do not match every product sold under the generic use." } ], "standards": [ { "market": "UK", "standard": "BS 8539 / ETAG 001 and EAD", "covers": "Selection and installation of post-installed anchors in concrete and masonry, and the European assessment route by which anchors are approved." }, { "market": "US", "standard": "ACI 318 Chapter 17 / ACI 355.2", "covers": "Anchoring to concrete including breakout and pullout, and qualification of post-installed mechanical anchors in concrete." } ], "calculators": [ { "slug": "brick-anchor-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/brick-anchor-spacing-calculator.json" }, { "slug": "cmu-anchor-embedment-calculator", "json": "https://craftquantities.com/api/v1/calculators/cmu-anchor-embedment-calculator.json" }, { "slug": "anchor-proof-load-test-calculator", "json": "https://craftquantities.com/api/v1/calculators/anchor-proof-load-test-calculator.json" }, { "slug": "post-installed-anchor-drill-depth-calculator", "json": "https://craftquantities.com/api/v1/calculators/post-installed-anchor-drill-depth-calculator.json" }, { "slug": "anchor-bolt-breakout-calculator", "json": "https://craftquantities.com/api/v1/calculators/anchor-bolt-breakout-calculator.json" }, { "slug": "structural-bolt-torque-calculator", "json": "https://craftquantities.com/api/v1/calculators/structural-bolt-torque-calculator.json" } ], "confusions": [ { "question": "Why is an anchor's stated load not the load it will carry?", "answer": "Because the published figure belongs to a TEST, and the test named a base material the job may not have. An anchor approval states the capacity in a defined material — a particular concrete strength, a particular solid or hollow unit — at a stated embedment, edge distance and spacing. Change any of those and the capacity changes, usually downward and sometimes by a large factor: the same anchor in solid concrete, in a dense block, in a lightweight aerated block and in a perforated clay brick are four different capacities, and in the lightweight block it may be a fraction of the headline. Edge distance and spacing matter because the failure is usually the CONE of base material pulling out rather than the steel breaking, and cones that reach an edge or overlap each other are smaller. So the honest reading of a datasheet number is the capacity of an anchor-and-material pair under stated geometry, and the first question on site is what the wall is actually made of." }, { "question": "When is a resin anchor the right choice over a mechanical one?", "answer": "In hollow or weak base materials, close to an edge, and where the fixing must not expand. A mechanical anchor works by expanding against the sides of the hole, which needs solid material to push against and generates a bursting force — so it performs badly in a hollow block, and near an edge it can split the masonry it is gripping. A resin anchor bonds along the whole depth of the hole instead, spreading load over a larger area and imposing no expansion force, which is why it is standard in perforated units with a mesh sleeve, in weak or historic masonry, and close to edges. Its cost is process discipline: the bond is only as good as the hole preparation, and a hole left full of dust can lose most of its capacity. It also has a curing time that varies sharply with temperature, and a load applied before the resin has cured is the most common way a correct specification fails on site." }, { "question": "What does proof loading prove, and what does it not?", "answer": "It proves the installation, not the design, and keeping that straight matters. A proof test applies a defined load — typically a multiple of the working load, well below the anchor's ultimate capacity — to installed anchors, and passes those that hold it without measurable movement. What it catches is the failure the calculation cannot see: a hole drilled too shallow, a wrong drill diameter, dust left in the hole, resin cured cold, an anchor in a void behind the surface. What it cannot tell you is whether the anchor is the right one, whether the base material is what the design assumed, or whether the anchor will still hold in twenty years, because a test to a working multiple deliberately does not go near failure. This is also why it is specified as a sample across a population rather than as a test of every fixing: it is a check on workmanship, and workmanship is the variable it is sampling." } ], "related": [ "wall-tie" ] }, { "slug": "plywood", "concept": "Plywood", "family": "materials", "definition": "A board of thin wood veneers glued with the grain of each layer crossing the last. The crossing is what makes it strong in both directions and stable; the glue decides where it can be used.", "url": "https://craftquantities.com/glossary/plywood/", "names": [ { "market": "UK", "term": "plywood", "alsoCalled": [ "ply", "WBP", "marine ply", "shuttering ply", "Class 3", "hardwood ply" ], "exactness": "false-friend", "note": "WBP is a withdrawn British grade still used in the trade. The current measure is a bonding CLASS 1 to 3, and MARINE PLY is a separate specification about veneer quality, not simply a better glue." }, { "market": "AU", "term": "plywood", "alsoCalled": [ "ply", "structural plywood", "A-bond", "form ply", "marine plywood" ], "exactness": "close", "note": "Uses a bond type A to D plus a face quality letter, so the label carries both properties separately — closer to European practice than to the American combined code." }, { "market": "US", "term": "plywood", "alsoCalled": [ "CDX", "ACX", "sheathing", "span rating", "exposure 1", "APA rated" ], "exactness": "false-friend", "note": "CDX is a FACE grade C, a back grade D and exterior glue. The X is the glue, not a quality — and Exposure 1 means it tolerates construction delays, not permanent exposure." }, { "market": "CA", "term": "plywood", "alsoCalled": [ "CSP", "Douglas fir plywood", "DFP", "sheathing grade", "select grade" ], "exactness": "false-friend", "note": "CSP is Canadian softwood plywood and is a distinct product from Douglas fir plywood, with different strengths — the two are not substitutes despite looking identical on a stack." } ], "standards": [ { "market": "UK", "standard": "BS EN 636 / BS EN 314-2", "covers": "Plywood specification including use classes for dry, humid and exterior conditions, and the bonding quality classes and their test requirements." }, { "market": "US", "standard": "PS 1 / APA product standards", "covers": "Structural plywood including veneer grades, glue bond classification and span ratings for sheathing applications." } ], "calculators": [ { "slug": "plywood-sheet-calculator", "json": "https://craftquantities.com/api/v1/calculators/plywood-sheet-calculator.json" }, { "slug": "roof-sheathing-nail-count-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-sheathing-nail-count-calculator.json" } ], "confusions": [ { "question": "Does the X in CDX mean exterior?", "answer": "It means exterior GLUE, which is not the same as an exterior board, and the difference has soaked a lot of roofs. The letters read in order: C is the face veneer grade, D is the back, and X indicates the bond will survive moisture. But the veneers themselves are low grades full of knots and voids, and the board as a whole is classified Exposure 1 — engineered to tolerate the weather during construction, not to live in it. So CDX left uncovered for a season delaminates at the edges, swells and never recovers its thickness. The genuinely exterior product is a different classification again, and for permanent wetting the answer is neither: it is a board specified for that service class. The comparable British trap is asking for WBP and receiving whatever the merchant calls WBP, since the grade was withdrawn and the term now means roughly weatherproof rather than anything testable." }, { "question": "Is marine plywood just plywood with better glue?", "answer": "No, and that misconception is why it disappoints. The glue in a good exterior plywood is already fully weatherproof — the same phenolic chemistry. What marine grade adds is VENEER quality and construction: veneers of a durable species, graded to permit very few defects, and above all no core VOIDS, because a void inside a board is a pocket that fills with water, cannot dry, and rots from the inside where nothing shows on either face. That is the property being bought, and it is about what is inside the sheet rather than what holds it together. Two consequences follow: marine grade is not automatically rot-proof, because the timber itself may not be durable unless the species says so and the edges are sealed; and for many wet applications a cheaper exterior board with sealed edges and a proper detail outperforms marine ply bought as a talisman." }, { "question": "What does a span rating tell you that a thickness does not?", "answer": "How far it can go between supports, in the direction that matters — which thickness alone cannot say because plywood is not equally strong both ways. The veneers alternate, but the FACE grain runs one way, and a sheet is substantially stiffer along that direction than across it. An American span rating is stamped as two numbers, the first for use as roof sheathing and the second as subfloor, and both assume the face grain runs ACROSS the supports, which is how the sheet is meant to be laid. Turn it ninety degrees to make the cuts work out and the rating no longer applies, even though the thickness is unchanged — a real and common site error that shows as a springy floor or a visibly sagging roof line between rafters. European practice publishes the bending properties for both directions instead of a single stamped rating, which is more information and rather less likely to be read at all." } ], "related": [ "osb" ] }, { "slug": "fall", "concept": "Fall and gradient", "family": "site", "definition": "The slope built into a drain, a gutter or a flat roof so that water runs off it. Quoted as the drop divided by the horizontal distance, in whichever of three conventions the market uses.", "url": "https://craftquantities.com/glossary/fall/", "names": [ { "market": "UK", "term": "fall", "alsoCalled": [ "gradient", "1 in 80", "self-cleansing velocity", "crossfall", "backfall" ], "exactness": "false-friend", "note": "Stated as a RATIO, 1 in 40 or 1 in 80. BACKFALL is the defect — a length sloping the wrong way — and is not a kind of fall but the absence of one." }, { "market": "AU", "term": "fall", "alsoCalled": [ "grade", "gradient", "percentage fall", "crossfall", "AS grade" ], "exactness": "close", "note": "Commonly a PERCENTAGE, so 1 in 100 is written 1%. The arithmetic is trivial and the confusion is not: 1 in 80 is 1.25%, which reads as a smaller number for a steeper slope." }, { "market": "US", "term": "slope", "alsoCalled": [ "pitch", "fall", "1/4 inch per foot", "grade", "cross slope" ], "exactness": "false-friend", "note": "Stated as INCHES PER FOOT — a quarter inch per foot is the usual drain minimum, equal to 1 in 48. PITCH here means slope, which is not the roof sense of the same word." }, { "market": "CA", "term": "slope", "alsoCalled": [ "grade", "fall", "1:50", "percent grade" ], "exactness": "false-friend", "note": "Mixes the American inches-per-foot habit with metric ratios written 1:50, so a single drawing can carry both and the units are not always stated on either." } ], "standards": [ { "market": "UK", "standard": "Approved Document H / BS EN 12056-2", "covers": "Drainage and waste disposal including minimum gradients for foul drains, and gravity drainage systems inside buildings." }, { "market": "US", "standard": "IPC 704 / UPC 708", "covers": "Drainage pipe slope requirements by pipe size, and the alternative plumbing code's cleanouts and slope provisions." } ], "calculators": [ { "slug": "drain-pipe-slope-calculator", "json": "https://craftquantities.com/api/v1/calculators/drain-pipe-slope-calculator.json" }, { "slug": "hvac-condensate-drain-slope-calculator", "json": "https://craftquantities.com/api/v1/calculators/hvac-condensate-drain-slope-calculator.json" }, { "slug": "low-slope-cricket-taper-calculator", "json": "https://craftquantities.com/api/v1/calculators/low-slope-cricket-taper-calculator.json" }, { "slug": "culvert-deflection-calculator", "json": "https://craftquantities.com/api/v1/calculators/culvert-deflection-calculator.json" } ], "confusions": [ { "question": "Why can a drain be laid too steeply?", "answer": "Because a drain has to carry solids, and solids need the water to stay with them. A foul drain works by the flow reaching a SELF-CLEANSING VELOCITY — fast enough to keep solids in suspension and scour the invert as it goes. Too shallow and the water crawls, solids settle out and the drain silts up. Too steep and the water runs away faster than the solids it was carrying, leaving them stranded on a dry pipe to dry out and block it. That is why minimum gradients are paired with maximums rather than being a floor to exceed, why a steep site uses a shallow-laid run with a backdrop manhole rather than one steep pipe, and why a length that has been re-laid steeper to clear an obstruction is a common cause of a blockage that keeps coming back at the same place." }, { "question": "Does a flat roof have a fall?", "answer": "Always, and a roof that does not is the problem rather than the design. FLAT means low-slope, not level: a roof that is genuinely level holds water, and standing water is the enemy of almost every waterproofing system — it finds the smallest defect, it multiplies the load, it grows organic matter, and in freezing climates it lifts the membrane. Guidance therefore specifies a DESIGN fall large enough that the finished roof still drains after construction tolerances and deflection have taken their share, which is why the design figure is roughly double the minimum anyone wants to end up with. The fall can be built into the deck, into firrings on top of the joists, or into a tapered insulation scheme cut to a scheme drawing — and the last is the one that goes wrong on site, because the boards are not interchangeable and a pallet laid in the wrong order produces a roof that ponds exactly where the scheme said it would drain." }, { "question": "How do the three conventions convert?", "answer": "By arithmetic that is easy and by a habit of mind that is not. A ratio of 1 in 80 means one unit of drop per eighty of run, which is 1.25 percent, which is 0.15 inches per foot. The trap is direction: in a RATIO the second number grows as the slope gets SHALLOWER, so 1 in 80 is gentler than 1 in 40, while in a percentage or an inches-per-foot figure a bigger number is a steeper slope. So a specification that reads *minimum 1 in 40* and one that reads *minimum 2%* are pulling in the same direction, and somebody converting carelessly can satisfy one while breaking the other. The safe practice on a drawing crossing markets is to state the drop and the run as two dimensions, which is unambiguous in every convention, and to put the ratio beside it rather than instead of it." } ], "related": [ "gully" ] }, { "slug": "shingle", "concept": "Shingle", "family": "envelope", "definition": "A small overlapping unit laid in courses to shed water down a slope. What it is made of, and whether the word means a roof covering at all, depends entirely on the market.", "url": "https://craftquantities.com/glossary/shingle/", "names": [ { "market": "UK", "term": "shingle", "alsoCalled": [ "cedar shingle", "shake", "gravel", "pea shingle", "felt shingle" ], "exactness": "false-friend", "note": "Most often means BEACH GRAVEL or graded aggregate. The roofing sense is wooden or bitumen shingles, a minority covering — the ordinary British roof is tiles or slates." }, { "market": "AU", "term": "shingle", "alsoCalled": [ "timber shingle", "shake", "roof tile", "metal roofing" ], "exactness": "false-friend", "note": "Rare as a roof covering, where concrete tile and profiled metal sheet dominate — so the word carries no assumption about the roof the way it does in North America." }, { "market": "US", "term": "shingle", "alsoCalled": [ "asphalt shingle", "composition shingle", "architectural shingle", "3-tab", "square" ], "exactness": "false-friend", "note": "The default roof covering, and quantities are counted in SQUARES of 100 square feet. ARCHITECTURAL means laminated and thicker, not a design category." }, { "market": "CA", "term": "shingle", "alsoCalled": [ "asphalt shingle", "laminate shingle", "square", "ice and water shield" ], "exactness": "false-friend", "note": "As the United States, with an ice-barrier membrane at the eaves effectively mandatory — a detail British specifications have no equivalent requirement for." } ], "standards": [ { "market": "UK", "standard": "BS 8000-6 / BS 5534", "covers": "Workmanship for slating and tiling of roofs and claddings, and the code of practice for slating and tiling including wind uplift fixing." }, { "market": "US", "standard": "ASTM D3462 / ASTM D7158", "covers": "Asphalt shingles made from glass felt and surfaced with mineral granules, and wind resistance of asphalt shingles by uplift classification." } ], "calculators": [ { "slug": "roofing-shingle-calculator", "json": "https://craftquantities.com/api/v1/calculators/roofing-shingle-calculator.json" }, { "slug": "slate-shingle-course-calculator", "json": "https://craftquantities.com/api/v1/calculators/slate-shingle-course-calculator.json" }, { "slug": "wood-shingle-triple-lap-calculator", "json": "https://craftquantities.com/api/v1/calculators/wood-shingle-triple-lap-calculator.json" } ], "confusions": [ { "question": "What is a square, and why is roofing sold in them?", "answer": "A SQUARE is one hundred square feet of finished roof surface — not of material, which is the distinction that matters when ordering. Shingles are sold in bundles that make up a fraction of a square, typically three bundles to one, and the number is expressed in squares because it makes the arithmetic of a roof easy in a trade that works in feet. The two ways it goes wrong on a job are worth separating. First, a square is the COVERED area after laps, so a bundle covers less roof than the material in it measures; the bundle count already accounts for that but a hand calculation from material area does not. Second, the area is of the roof SLOPE rather than of the building footprint, so a plan area has to be divided by the cosine of the pitch before anything is ordered. Both errors under-order, and a roof short by half a square stops at the worst possible moment." }, { "question": "What is the difference between a shingle and a shake?", "answer": "How the wood was separated, and it changes both the look and the performance. A SHINGLE is sawn, so both faces are flat and the taper is even; a SHAKE is split along the grain, so at least one face is riven and irregular and the thickness varies. Splitting follows the wood's natural fibres rather than cutting across them, which makes a shake more durable and more resistant to water travelling along a cut grain — and rougher, thicker and considerably more expensive. The practical consequence is in the underlay: a shake roof's irregular surface leaves gaps between courses, so interlayment strips are laid between them, where a sawn shingle roof sits tight enough not to need it. In British usage both words appear only in specialist work, which is why the distinction is usually met first in an American specification where it is assumed knowledge." }, { "question": "Why does a British roof use tiles where an American one uses shingles?", "answer": "Climate, fire history and the cost of the local material, in that order of effect. British roofs are pitched steeply and see persistent driving rain rather than extreme heat, and clay and slate were quarried locally and last a century or more, so the covering that became standard is a heavy, rigid unit hung on battens. North American housing built out in timber at speed over a continent with no comparable slate industry, and an asphalt strip nailed directly to a sheathing deck was faster, lighter and did not need a structure designed to carry it. The consequence for anyone reading across markets is structural rather than cosmetic: a tiled roof weighs several times what a shingled one does, so a rafter and wall design sized for one will not simply accept the other, and re-covering a roof in the other market's material is a structural question before it is a roofing one." } ], "related": [ "ridge" ] }, { "slug": "mvhr", "concept": "Ventilation with heat recovery", "family": "services", "definition": "A ducted system that extracts stale air and supplies fresh air continuously, passing the two streams through a heat exchanger so the outgoing air warms the incoming air without mixing.", "url": "https://craftquantities.com/glossary/mvhr/", "names": [ { "market": "UK", "term": "MVHR", "alsoCalled": [ "mechanical ventilation with heat recovery", "heat recovery ventilation", "MEV", "System 4" ], "exactness": "false-friend", "note": "MEV is a different system entirely — continuous mechanical EXTRACT with no supply and no recovery — and the two are routinely confused because the acronyms differ by one letter." }, { "market": "AU", "term": "HRV", "alsoCalled": [ "heat recovery ventilation", "ERV", "balanced ventilation", "mechanical ventilation" ], "exactness": "close", "note": "Far less common than in cold climates, since the heat being recovered is worth less; where it appears in a humid zone the ERV variant is usually the right one." }, { "market": "US", "term": "HRV", "alsoCalled": [ "ERV", "heat recovery ventilator", "energy recovery ventilator", "balanced ventilation" ], "exactness": "false-friend", "note": "HRV and ERV are separate products: an ERV transfers MOISTURE as well as heat. Which is correct depends on the climate zone, and the wrong one makes a house drier or damper than intended." }, { "market": "CA", "term": "HRV", "alsoCalled": [ "heat recovery ventilator", "ERV", "air exchanger", "HVI rating" ], "exactness": "close", "note": "Effectively standard in new housing, and rated by HVI at two temperatures because a unit's efficiency and its frost behaviour are different questions." } ], "standards": [ { "market": "UK", "standard": "Approved Document F / BS 5720", "covers": "Ventilation requirements including continuous mechanical supply and extract rates, and the code of practice for mechanical ventilation of buildings." }, { "market": "US", "standard": "ASHRAE 62.2 / HVI 920", "covers": "Ventilation and acceptable indoor air quality in residential buildings, and the product rating procedure for heat and energy recovery ventilators." } ], "calculators": [ { "slug": "erv-hrv-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/erv-hrv-sizing-calculator.json" }, { "slug": "erv-sensible-recovery-calculator", "json": "https://craftquantities.com/api/v1/calculators/erv-sensible-recovery-calculator.json" }, { "slug": "air-changes-per-hour-calculator", "json": "https://craftquantities.com/api/v1/calculators/air-changes-per-hour-calculator.json" }, { "slug": "kitchen-hood-exhaust-cfm-calculator", "json": "https://craftquantities.com/api/v1/calculators/kitchen-hood-exhaust-cfm-calculator.json" } ], "confusions": [ { "question": "What is the difference between an HRV and an ERV?", "answer": "Moisture. Both pass the outgoing and incoming air streams either side of a heat exchanger so that heat crosses without the air mixing. An HRV's core transfers SENSIBLE heat only — temperature. An ERV's core is made of a material that also transfers water vapour, so some of the humidity crosses with the heat. In a humid summer that is an advantage: the outgoing conditioned air dries the incoming muggy air before it reaches the cooling coil, which cuts the latent load substantially. In a cold, dry winter it is a different trade: the ERV returns moisture to the house that an HRV would have thrown away, which keeps indoor humidity up — comfortable, and a problem if the building already struggles with condensation. So it is a climate decision and a building decision rather than a quality ladder, and specifying an ERV because it sounds like the upgraded model is the common error." }, { "question": "Why does a heat recovery unit need a frost strategy?", "answer": "Because the air it is cooling is the air people have been breathing into. The extract stream leaves the house warm and humid; inside the exchanger it is cooled by the incoming outdoor air, and once its temperature drops below its dew point it deposits water on the core. If the incoming air is below freezing, that water becomes ice, the ice blocks the extract side, the flow falls and the unit's efficiency collapses — in the coldest week, when it is needed most. Units therefore carry a defrost strategy: a pre-heater on the incoming air, a periodic recirculation cycle, or throttling the supply fan to let the warm stream melt the core. Each costs something — energy, ventilation rate, or balance — and the fact that this is a designed behaviour rather than a fault is why a system that seems to stop working in a cold snap is usually doing exactly what it was set up to do." }, { "question": "Why is commissioning the ductwork as important as the unit?", "answer": "Because the recovery figure on the box is a property of the core, and everything a household actually experiences is a property of the installation. The unit only recovers heat if the two air streams are BALANCED: if extract exceeds supply the house is depressurised and pulls unconditioned air in through every gap, and if supply exceeds extract it is pressurised and pushes humid air into the construction. Balancing means measuring the flow at each terminal and adjusting, not setting a speed and assuming. The ducts themselves decide the rest: flexible duct pulled tight around a bend can lose most of the flow to that branch, insufficiently insulated duct in a cold loft condenses on its outside and drips through a ceiling, and a run that was shortened on site changes the balance of every other branch. That is why a commissioning sheet with measured flows is the deliverable, and why a system installed without one is a box with no evidence it does anything." } ], "related": [ "airtightness", "ductwork" ] }, { "slug": "lead-paint", "concept": "Lead paint", "family": "materials", "definition": "Paint containing lead compounds, used for durability and colour before it was restricted. The hazard is the DUST from disturbing it, not the intact film on the wall.", "url": "https://craftquantities.com/glossary/lead-paint/", "names": [ { "market": "UK", "term": "lead paint", "alsoCalled": [ "lead-based paint", "red lead", "white lead", "lead in paint regulations" ], "exactness": "false-friend", "note": "No single presumption year. Domestic sale was restricted progressively and late, so an older house may carry lead under later coats with no date that rules it out." }, { "market": "AU", "term": "lead paint", "alsoCalled": [ "lead-based paint", "pre-1970 paint", "lead dust", "lead safe work" ], "exactness": "close", "note": "Guidance treats pre-1970 housing as likely and 1970s housing as possible, and the permitted lead content of new paint has been cut several times since." }, { "market": "US", "term": "lead-based paint", "alsoCalled": [ "LBP", "pre-1978", "RRP rule", "renovate repair and paint", "lead-safe certified", "disclosure" ], "exactness": "false-friend", "note": "1978 is a legal bright line. Pre-1978 housing triggers disclosure on sale or lease, and paid renovation work triggers certified firms and specified work practices." }, { "market": "CA", "term": "lead paint", "alsoCalled": [ "lead-based paint", "pre-1960 paint", "lead dust", "lead abatement" ], "exactness": "close", "note": "Consumer paint limits tightened around 1976 and again later, with pre-1960 coatings the ones most likely to carry high concentrations rather than traces." } ], "standards": [ { "market": "UK", "standard": "Control of Lead at Work Regulations 2002 / HSE guidance", "covers": "Duties where work exposes people to lead including assessment, control and medical surveillance, and practical guidance on paint removal." }, { "market": "US", "standard": "40 CFR 745 Subpart E (RRP) / HUD Guidelines", "covers": "Renovation, repair and painting certification and work practices in pre-1978 housing, and evaluation and control of lead-based paint hazards." } ], "calculators": [ { "slug": "exterior-paint-calculator", "json": "https://craftquantities.com/api/v1/calculators/exterior-paint-calculator.json" }, { "slug": "paint-primer-calculator", "json": "https://craftquantities.com/api/v1/calculators/paint-primer-calculator.json" } ], "confusions": [ { "question": "Is intact lead paint on a wall dangerous?", "answer": "Largely not, and that is the whole basis of how it is regulated. Lead in a sound, adhered film is not going anywhere: the exposure route that matters is DUST and fumes, created when the film is sanded, scraped, burnt off, blasted or allowed to deteriorate into flaking chalk. So the risk is a property of the CONDITION and of what is about to be done to it, rather than of the presence of lead. The two circumstances that turn it into a hazard are disturbance by work and deterioration over time — plus a third that is specific to housing: friction surfaces. A painted sash window or a door rubbing in its frame grinds lead paint into dust every time it is used, which is why those are singled out in guidance even where the rest of the house is sound. The default advice therefore mirrors asbestos: leave a sound coating in place, encapsulate or overcoat it, and manage what disturbs it." }, { "question": "Why is a heat gun the wrong tool, and what is the right one?", "answer": "Because lead fumes at a temperature below what a heat gun produces on its hot setting, and fume is inhaled far more readily than dust. Paint softens well below that, so the safe use of heat is a low setting with a thermometer and constant movement — which is slow, and which is why most people turn it up. The tools that generate the worst exposure are exactly the fast ones: an open flame, a heat gun on full, dry power sanding, and abrasive blasting. What is recommended instead is either removal that keeps the dust wet and heavy — wet scraping, wet sanding, chemical stripping — or removal that captures it at source with a shrouded sander on a filtered vacuum. Ordinary vacuums are their own hazard: a domestic cleaner without the right filtration passes fine lead dust straight through and distributes it around the room more evenly than sweeping would." }, { "question": "Why does the American 1978 date not help in Britain?", "answer": "Because it is a legal presumption attached to a specific regulatory scheme, not a fact about paint chemistry. The United States banned lead in consumer paint in 1978, so American law can treat that year as a bright line: pre-1978 housing carries disclosure duties on sale or lease, and paid work on it triggers certification and prescribed practices. Britain restricted domestic paint later and progressively rather than at a single stroke, and never attached a housing-age presumption of the same kind, so there is no year that clears a British property and no automatic disclosure duty of that shape. The practical consequences are opposite. In the United States the age of the building tells you which rules apply. In Britain it tells you only that lead is plausible, and the way to find out is to test the surface — which is also why an American method statement applied to a British job can be simultaneously more prescriptive than the law requires and silent about the assessment the law does require." } ], "related": [ "asbestos" ] }, { "slug": "decking", "concept": "Decking", "family": "structure", "definition": "Boards laid across supports to form a surface. Whether that surface is an outdoor platform or the structural deck of a roof or floor depends on the market and the sentence.", "url": "https://craftquantities.com/glossary/decking/", "names": [ { "market": "UK", "term": "decking", "alsoCalled": [ "deck boards", "garden decking", "composite decking", "joists", "deck frame" ], "exactness": "false-friend", "note": "Means the outdoor platform, effectively always. The structural sense — a roof or floor deck — is called SHEATHING or boarding here, never decking." }, { "market": "AU", "term": "decking", "alsoCalled": [ "deck", "deck boards", "bearers and joists", "merbau decking" ], "exactness": "close", "note": "As British usage, with BEARERS naming the beams under the joists — a member British practice usually calls a beam and American practice calls a girder or a beam." }, { "market": "US", "term": "decking", "alsoCalled": [ "deck boards", "roof decking", "floor decking", "sheathing", "metal deck", "ledger" ], "exactness": "false-friend", "note": "Covers both the outdoor platform AND the structural deck of a roof or floor, including profiled metal deck in commercial work. The sentence has to disambiguate it." }, { "market": "CA", "term": "decking", "alsoCalled": [ "deck boards", "roof deck", "sheathing", "ledger board" ], "exactness": "false-friend", "note": "As the United States, with frost depth governing the deck's footings so strongly that a modest deck needs the same founding depth as the house it is attached to." } ], "standards": [ { "market": "UK", "standard": "BS 8103-3 / TDCA guidance", "covers": "Structural design of timber floors and roofs in low-rise housing, and industry guidance on the design and installation of timber decking." }, { "market": "US", "standard": "IRC R507 / AWC DCA 6", "covers": "Exterior decks including ledger attachment and lateral load connection, and the prescriptive residential wood deck construction guide." } ], "calculators": [ { "slug": "deck-board-calculator", "json": "https://craftquantities.com/api/v1/calculators/deck-board-calculator.json" }, { "slug": "deck-joist-span-calculator", "json": "https://craftquantities.com/api/v1/calculators/deck-joist-span-calculator.json" }, { "slug": "deck-ledger-flashing-calculator", "json": "https://craftquantities.com/api/v1/calculators/deck-ledger-flashing-calculator.json" }, { "slug": "ledger-lag-screw-count-calculator", "json": "https://craftquantities.com/api/v1/calculators/ledger-lag-screw-count-calculator.json" }, { "slug": "corrugated-decking-deflection-calculator", "json": "https://craftquantities.com/api/v1/calculators/corrugated-decking-deflection-calculator.json" } ], "confusions": [ { "question": "Why is the ledger the part that actually fails?", "answer": "Because it is the one connection carrying the whole deck into the house, and the two ways it is commonly built are both wrong. A deck attached to a building hangs off a LEDGER board fixed to the structure, and that fixing takes the full vertical load of everything on the deck plus, in a code that requires it, a lateral tie resisting the deck pulling away. Nailing the ledger on is the first error — nails withdraw under sustained load in a way bolts do not — and the prescriptive guides specify bolts or approved structural screws at a stated pattern for that reason. The second is water: a ledger bolted tight to a wall with no flashing traps every drop running down the face behind it, and the rot that follows is invisible until the deck comes away with people on it. Deck collapses are overwhelmingly ledger failures at a gathering, which is also why some designs avoid the question entirely with a freestanding deck on its own posts." }, { "question": "Does composite decking need less maintenance or different maintenance?", "answer": "Different, and the marketing claim is narrower than it sounds. A wood-plastic composite board will not rot, will not splinter and does not need oiling or staining, which removes the annual job that makes timber decking unpopular. What it does instead: it expands and contracts with temperature considerably more than timber does, so the fixing pattern and end gaps are specified by the manufacturer and are not optional — a board fixed tight at both ends in winter buckles in summer. It gets hotter underfoot in direct sun than timber. It still grows algae and still needs cleaning, because the film that makes a deck slippery is organic matter on the surface rather than a property of the material. And it is not structural, so the joists and bearers underneath are still timber with a timber's lifespan. The honest summary is a change in the maintenance task rather than its removal." }, { "question": "How do I tell which decking an American drawing means?", "answer": "By what it is attached to and how it is measured. If the drawing calls up a span rating, a nailing schedule, sheathing thickness or a fastener pattern over rafters or floor joists, it means the structural deck — the sheet material a roof covering or a floor finish is laid over. If it names board widths, gaps, a ledger, posts, footings or a railing, it means the outdoor platform. Two further signals are reliable: profiled METAL deck is always the structural sense, and anything specifying a gap between boards is always the platform sense, because a structural deck is laid tight. The distinction matters commercially as well as technically, because the two sit in different trades and different sections of a bill — confusing them in a takeoff produces a quantity in the right units for entirely the wrong work." } ], "related": [ "joist" ] }, { "slug": "slab-on-grade", "concept": "Ground floor slab", "family": "structure", "definition": "A concrete floor cast on prepared ground rather than spanning between supports. What varies is whether it also carries the structure above, or only the floor and its contents.", "url": "https://craftquantities.com/glossary/slab-on-grade/", "names": [ { "market": "UK", "term": "ground bearing slab", "alsoCalled": [ "oversite", "ground floor slab", "suspended slab", "raft", "beam and block" ], "exactness": "false-friend", "note": "A GROUND BEARING slab carries the floor only; the walls sit on their own foundations. A RAFT is the different case where the slab carries everything — different reinforcement, different design." }, { "market": "AU", "term": "slab on ground", "alsoCalled": [ "waffle raft", "stiffened raft", "footing slab", "slab-on-grade" ], "exactness": "false-friend", "note": "Usually a stiffened RAFT that carries the walls, with beams cast integrally and sized against the site's soil reactivity class — not the British ground-bearing arrangement at all." }, { "market": "US", "term": "slab on grade", "alsoCalled": [ "monolithic slab", "thickened edge slab", "floating slab", "post-tensioned slab", "vapor retarder" ], "exactness": "false-friend", "note": "MONOLITHIC means the slab and its thickened edge footing are one pour carrying the walls. A FLOATING slab is the separate case where the slab is independent of the foundation." }, { "market": "CA", "term": "slab on grade", "alsoCalled": [ "floating slab", "frost-protected shallow foundation", "basement slab", "under-slab insulation" ], "exactness": "close", "note": "Frost depth usually forces a separate foundation below the slab, so the monolithic detail common further south is the exception rather than the default." } ], "standards": [ { "market": "UK", "standard": "BS 8204-1 / BS 8102", "covers": "Screeds and in-situ floorings on concrete bases, and protection of below-ground structures against water from the ground." }, { "market": "US", "standard": "ACI 302.1R / ASTM E1745", "covers": "Guide to concrete floor and slab construction, and the specification for plastic water vapor retarders used under concrete slabs." } ], "calculators": [ { "slug": "reverse-concrete-slab-calculator", "json": "https://craftquantities.com/api/v1/calculators/reverse-concrete-slab-calculator.json" }, { "slug": "under-slab-perimeter-foam-calculator", "json": "https://craftquantities.com/api/v1/calculators/under-slab-perimeter-foam-calculator.json" }, { "slug": "one-way-slab-thickness-calculator", "json": "https://craftquantities.com/api/v1/calculators/one-way-slab-thickness-calculator.json" } ], "confusions": [ { "question": "Does a ground slab carry the walls?", "answer": "Sometimes, and it is the first thing to establish because everything else follows from it. In the common British arrangement the walls stand on their own strip or trench-fill foundations and the slab spans nothing — it carries the floor finish, the furniture and the people, bearing directly on compacted hardcore. In a RAFT, an Australian stiffened slab, or an American monolithic slab, the slab and its thickened edges ARE the foundation: the walls sit on them, and the reinforcement, the edge geometry and the ground preparation are all designed for that. The two look similar on a site photograph and are not interchangeable. Loading a ground-bearing slab as though it were a raft is the failure that follows, and it is silent at first: the slab cracks along the line of the load, and the wall it is carrying settles differentially with it." }, { "question": "Why does the membrane go under the slab and not over it?", "answer": "Because concrete is porous and the vapour is coming up. A damp-proof membrane placed on top of the slab keeps ground moisture out of the floor finish but leaves the slab itself permanently wet from below, which in turn keeps any adhesive, timber or screed above it at risk and stops the slab ever drying. Placed UNDER the slab, on sand blinding over the hardcore, it stops moisture entering the concrete at all, and the slab dries upward as it cures. There is a second reason specific to the American practice of pouring directly onto the retarder: a slab sitting on an impermeable sheet can only bleed water upward, which affects finishing and curing and has been argued about for decades — hence the standard specifically for under-slab vapour retarders and the arguments about a blotter layer over it. What both markets agree on is that the membrane belongs under the concrete and must be lapped and sealed into the wall's damp-proof course, because an unconnected membrane is a tray with an open edge." }, { "question": "Where does the insulation go, and does the edge matter more than the middle?", "answer": "The edge matters far more, and this is the least intuitive thing about a ground floor. Heat leaving the middle of a slab travels a long way through soil before it reaches anywhere cold, and soil at depth stays close to the annual average temperature — so the centre of a large floor loses heat slowly whatever is under it. At the PERIMETER the path is short: a few centimetres of concrete to the outside air, through an edge that is also a structural junction. The result is that heat loss through a ground floor is concentrated in a band around its edge, that the loss per square metre falls as the floor gets bigger, and that edge or perimeter insulation buys most of the benefit of a fully insulated floor for a fraction of the material. It is also why the slab edge is one of the worst thermal bridges in a building and why the detail there — insulation turned down the edge, or a thermally broken upstand — decides the floor's real performance more than the thickness under the middle." } ], "related": [ "hardcore" ] }, { "slug": "window-type", "concept": "Window opening types", "family": "envelope", "definition": "How a window opens: hinged at a side, at the top or bottom, sliding vertically or horizontally, or not at all. The names for these differ more between markets than the mechanisms do.", "url": "https://craftquantities.com/glossary/window-type/", "names": [ { "market": "UK", "term": "casement", "alsoCalled": [ "sash window", "top hung", "side hung", "tilt and turn", "fixed light", "fanlight" ], "exactness": "false-friend", "note": "SASH WINDOW means the vertically sliding box sash specifically. A FANLIGHT is the small opening light above a window or door, not a fan and not always a light." }, { "market": "AU", "term": "awning window", "alsoCalled": [ "casement", "double hung", "sliding window", "louvre window" ], "exactness": "close", "note": "AWNING — top-hung, opening outward — is common enough to be a default here and is rare in British housing, while LOUVRE windows appear in a way they do not in cold climates." }, { "market": "US", "term": "double-hung", "alsoCalled": [ "single-hung", "sash", "casement", "awning", "hopper", "slider", "picture window" ], "exactness": "false-friend", "note": "SASH means the moving frame of any window, so every casement has sashes. HOPPER is bottom-hung inward, AWNING top-hung outward, and neither has a common British name." }, { "market": "CA", "term": "casement", "alsoCalled": [ "double-hung", "awning", "hopper", "slider", "egress window" ], "exactness": "close", "note": "Casement is more common than in the United States because it seals better against cold, and EGRESS WINDOW names a code requirement about escape rather than a style." } ], "standards": [ { "market": "UK", "standard": "BS 6375-1 / Approved Document B", "covers": "Performance of windows including weathertightness classification, and the means of escape requirements that govern openable area and dimensions." }, { "market": "US", "standard": "AAMA/WDMA/CSA 101 / IRC R310", "covers": "North American fenestration standard including performance class and operator type designations, and emergency escape and rescue opening requirements." } ], "calculators": [ { "slug": "fenestration-rough-opening-calculator", "json": "https://craftquantities.com/api/v1/calculators/fenestration-rough-opening-calculator.json" }, { "slug": "skylight-rough-opening-calculator", "json": "https://craftquantities.com/api/v1/calculators/skylight-rough-opening-calculator.json" }, { "slug": "window-wall-u-factor-calculator", "json": "https://craftquantities.com/api/v1/calculators/window-wall-u-factor-calculator.json" } ], "confusions": [ { "question": "Why does a casement seal better than a hung window?", "answer": "Because of how the closing action meets the seal. A casement swings shut against a continuous gasket and is then pulled tight by its locking points, so the seal is compressed all the way round — the harder the wind pushes, the tighter a correctly hung outward-opening casement closes. A vertically sliding window cannot do that: the sashes have to slide past each other and past the frame, so the contact is a sliding fit with brushes or a compression seal only where the meeting rails come together. That gap is the reason an old sliding sash window is draughty and the reason its modern equivalents work hard on the meeting rail. The trade-offs run the other way in other respects — a hung window projects into nothing when open, which matters on a footpath or a balcony, and it ventilates at top and bottom at once, which drives a useful stack effect a casement cannot." }, { "question": "What is an egress window, and does Britain have the same rule?", "answer": "It is a window sized and positioned so a person can escape through it and a firefighter can get in, and both markets require something like it while defining it differently. American residential code sets explicit minimums for a bedroom or basement: a clear opening area, a minimum clear height and width, and a maximum sill height above the floor — four numbers, all of which must be met by the CLEAR opening with the window fully open, not by the frame's nominal size. British guidance sets an unobstructed openable area and a minimum dimension with a sill height range instead, and applies it to upper-storey habitable rooms and to inner rooms rather than to bedrooms as a class. The trap either way is the same: replacing a window like for like in overall size can fail the requirement, because a modern frame's sections and its opening mechanism eat into the clear opening that the old one had." }, { "question": "Why does the word sash cause so much confusion?", "answer": "Because it names a component in one market and a product in the other, and both usages are correct where they live. In North America a SASH is the glazed frame that moves — or does not — inside the outer frame, so a casement has a sash, a double-hung has two, and a manufacturer's parts list talks about sash replacement for any window type. In Britain SASH WINDOW is a specific thing: the traditional vertically sliding window with weights in a boxed frame, cords over pulleys, and a pair of sashes that counterbalance. So a British reader meeting the phrase *casement sash* reads a contradiction, and an American reader meeting *sash window* reads a redundancy. The practical fix in a cross-market specification is to name the OPERATION rather than the product — side-hung, top-hung, vertically sliding — because those phrases mean the same thing everywhere and no market has claimed them for something else." } ], "related": [ "threshold" ] }, { "slug": "guardrail", "concept": "Guard and handrail", "family": "structure", "definition": "The barrier that stops a person falling from a change in level, and the rail a person holds while using a stair. Separate elements with separate heights and separate loadings, whatever they are called.", "url": "https://craftquantities.com/glossary/guardrail/", "names": [ { "market": "UK", "term": "guarding", "alsoCalled": [ "balustrade", "handrail", "barrier", "edge protection", "infill" ], "exactness": "false-friend", "note": "GUARDING is the regulatory word for the barrier and HANDRAIL for the grip, but BALUSTRADE is used in the trade for both together — which is where the two requirements get merged into one." }, { "market": "AU", "term": "balustrade", "alsoCalled": [ "barrier", "handrail", "guardrail", "infill" ], "exactness": "false-friend", "note": "BALUSTRADE is the code's own word for the barrier here, with the handrail named separately, so the same word is a regulatory term in Australia and trade shorthand in Britain." }, { "market": "US", "term": "guard", "alsoCalled": [ "guardrail", "handrail", "baluster", "top rail", "graspable" ], "exactness": "false-friend", "note": "GUARD and HANDRAIL are distinct code elements at different heights, and a stair usually needs both. GRASPABLE is a defined shape requirement for the handrail, not a description." }, { "market": "CA", "term": "guard", "alsoCalled": [ "guardrail", "handrail", "balustrade", "climbable" ], "exactness": "false-friend", "note": "As the United States, with the CLIMBABLE restriction on horizontal members in a guard written explicitly — a rule British guidance expresses through the sphere test instead." } ], "standards": [ { "market": "UK", "standard": "Approved Document K / BS 6180", "covers": "Protection from falling, collision and impact including guarding heights, and the code of practice for barriers in and about buildings with their design loads." }, { "market": "US", "standard": "IRC R312 / IBC 1015", "covers": "Guards for residential construction including height and opening limitations, and the commercial guard requirements with loading and opening criteria." } ], "calculators": [ { "slug": "guardrail-compliance-checker", "json": "https://craftquantities.com/api/v1/calculators/guardrail-compliance-checker.json" }, { "slug": "guardrail-post-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/guardrail-post-spacing-calculator.json" }, { "slug": "handrail-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/handrail-length-calculator.json" }, { "slug": "glass-balustrade-stress-calculator", "json": "https://craftquantities.com/api/v1/calculators/glass-balustrade-stress-calculator.json" } ], "confusions": [ { "question": "What is the difference between a guard and a handrail?", "answer": "What they are for, which sets everything else about them. A GUARD is a barrier at the edge of a drop: its job is to stop a person, a child or a pushed object going over, so it is specified by HEIGHT above the walking surface, by the size of gap it may contain, and by a horizontal load it must resist along its top. A HANDRAIL is something to hold: its job is to steady a person and arrest a slip on a stair, so it is specified by a graspable cross-section, a height that suits a hand rather than a body, continuity along the flight, and often an extension past the top and bottom step. A stair beside a drop usually needs both, and they are at different heights — which is why an American stair often shows a low handrail mounted on the posts of a taller guard, a detail that looks redundant to anyone who thinks of the whole thing as one balustrade." }, { "question": "Why is a horizontal rail a problem?", "answer": "Because a child climbs it, and the guard's height is measured from the floor rather than from the last thing a child can stand on. A guard made of horizontal rails is a ladder: a toddler can reach the top rail of a compliant guard in a few seconds, and the effective height of the barrier becomes the distance from the highest foothold to the top, which may be a fraction of what the drawing says. Canadian and American codes address this directly by restricting climbable members within a defined zone of the guard. British guidance reaches the same place from a different direction: it requires that guarding in a building where children under five may be present should not be readily climbable, and applies the sphere test — no gap that a 100 mm sphere can pass — to the openings. The design consequence is the same in all three: vertical infill, glass, mesh or solid panels, and horizontal rails only where the building will not have small children in it." }, { "question": "What does the load on a guard actually represent?", "answer": "A crowd leaning, not a person tripping — and that is why the figure varies so much with the building's use. A barrier is designed for a horizontal line load applied along its top, and the value depends on what is behind it: a domestic stair carries a small figure because the worst realistic case is one person losing balance, while a grandstand, a balcony at an assembly building or a barrier at the front of a queue carries a figure several times larger, because the design case is many people pressing. There is usually also a separate uniformly distributed load on the infill and a point load, since a guard can fail by a panel giving way rather than by the whole assembly moving. The practical consequences are two: the guard's load case comes from the OCCUPANCY rather than from the height of the drop, and the fixing at the base is almost always the governing detail, because a line load at the top of a post is a large moment at its foot." } ], "related": [ "baluster" ] }, { "slug": "flat-roof-covering", "concept": "Flat roof covering", "family": "envelope", "definition": "The waterproof layer on a low-slope roof. Named by material in some markets and by build-up in others, and held down in one of three ways that decide most of its design.", "url": "https://craftquantities.com/glossary/flat-roof-covering/", "names": [ { "market": "UK", "term": "felt roof", "alsoCalled": [ "built-up felt", "torch-on", "single ply", "EPDM", "liquid applied", "mastic asphalt" ], "exactness": "false-friend", "note": "FELT ranges from a shed's one-layer covering to a three-layer reinforced bitumen system with a thirty-year life. The word says nothing about the specification." }, { "market": "AU", "term": "membrane roof", "alsoCalled": [ "torch-on membrane", "liquid membrane", "TPO", "EPDM", "sheet membrane" ], "exactness": "close", "note": "MEMBRANE is the general word and the material is named after it, so an Australian specification tends to be explicit where a British one can be ambiguous." }, { "market": "US", "term": "low-slope roofing", "alsoCalled": [ "BUR", "built-up roof", "mod bit", "modified bitumen", "TPO", "EPDM", "PVC", "ballasted" ], "exactness": "false-friend", "note": "FLAT ROOF is avoided in the trade because no roof is flat; the products are named individually, and BUR and MOD BIT are different systems rather than grades of one." }, { "market": "CA", "term": "low-slope roofing", "alsoCalled": [ "BUR", "SBS", "modified bitumen", "TPO", "protected membrane", "inverted roof" ], "exactness": "close", "note": "PROTECTED MEMBRANE — insulation laid OVER the waterproofing rather than under it — is common here for freeze-thaw reasons and is the inverted roof of British usage." } ], "standards": [ { "market": "UK", "standard": "BS 6229 / BS 8217", "covers": "Flat roofs with continuously supported flexible waterproof coverings, and the code of practice for reinforced bitumen membranes." }, { "market": "US", "standard": "ASTM D6878 / FM 4470", "covers": "Thermoplastic polyolefin sheet roofing, and the approval standard for single-ply and other roof systems covering wind uplift and fire." } ], "calculators": [ { "slug": "epdm-roll-area-calculator", "json": "https://craftquantities.com/api/v1/calculators/epdm-roll-area-calculator.json" }, { "slug": "epdm-seam-tape-calculator", "json": "https://craftquantities.com/api/v1/calculators/epdm-seam-tape-calculator.json" }, { "slug": "waterproofing-membrane-roll-calculator", "json": "https://craftquantities.com/api/v1/calculators/waterproofing-membrane-roll-calculator.json" }, { "slug": "roof-uplift-zone-pressure-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-uplift-zone-pressure-calculator.json" }, { "slug": "roof-scupper-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-scupper-sizing-calculator.json" } ], "confusions": [ { "question": "What actually holds a flat roof down?", "answer": "One of three things, and which one decides most of the rest of the design. A FULLY ADHERED system is glued to the substrate over its whole area, which gives the best wind performance and the least tolerance for a damp or dusty deck. A MECHANICALLY FASTENED system is screwed through into the deck along the laps, which is fast and cheap and puts thousands of penetrations through the insulation — each one a small thermal bridge, and each one a potential leak if the deck below is not what the fixing schedule assumed. A BALLASTED system is held down by weight: gravel, pavers or a green roof build-up, which imposes a substantial dead load the structure has to have been designed for. The design question is wind UPLIFT, which is highest at the corners, then the edges, then the field — so a specification that quotes one fixing rate for the whole roof has usually been taken from the field figure and under-fixed the corners, which is exactly where roofs lift." }, { "question": "What is an inverted or protected membrane roof, and why turn the build-up upside down?", "answer": "The waterproofing goes UNDER the insulation instead of over it, and the insulation is then held down by ballast. The point is that the membrane — the expensive, vulnerable, difficult-to-repair layer — spends its life at a nearly constant temperature, protected from ultraviolet light, from foot traffic and from the daily thermal cycling that ages it, instead of being the hottest and coldest surface on the building. The cost is that the insulation is now outside the waterproofing and standing in water whenever it rains, so it has to be a closed-cell board that does not absorb it — in practice extruded polystyrene — and its performance has to be derated for the water that flows over it. It also means the roof cannot be inspected by looking at it. Where freeze-thaw is severe, or where a roof will be walked on or planted, the trade is usually worth making; on a small domestic extension it rarely is." }, { "question": "Why does a flat roof fail at the details rather than in the middle?", "answer": "Because the middle is a single sheet of waterproofing and the details are junctions, and every junction is a change of plane, a change of material or a penetration. The recurring four are worth naming. UPSTANDS: the membrane has to turn up at every abutment by enough that water driven up the roof cannot get over it, and be mechanically held at the top rather than relying on adhesion. OUTLETS: an outlet set above the finished surface guarantees ponding around it, and one with no overflow turns a blockage into a structural load. PENETRATIONS: pipes, vents and fixings each need a collar, and a mastic fillet is a repair rather than a detail. And the PERIMETER, where uplift is highest and where the edge trim is the thing holding the membrane against it. A roof that leaks in its field usually has damage; a roof that leaks at a detail was usually built that way, which is why the detail drawings are the deliverable that matters on a flat roof." } ], "related": [ "flashing" ] }, { "slug": "suspended-ceiling", "concept": "Suspended ceiling", "family": "finishes", "definition": "A ceiling hung below the structure on wires or hangers, leaving a void for services. Either a demountable grid holding lay-in tiles, or a concealed metal frame carrying boards.", "url": "https://craftquantities.com/glossary/suspended-ceiling/", "names": [ { "market": "UK", "term": "suspended ceiling", "alsoCalled": [ "MF ceiling", "grid ceiling", "lay-in grid", "plenum", "ceiling void", "tegular" ], "exactness": "false-friend", "note": "MF CEILING is the concealed metal-furring frame carrying plasterboard, a different product from the demountable grid — and SUSPENDED FLOOR means something unrelated." }, { "market": "AU", "term": "suspended ceiling", "alsoCalled": [ "grid ceiling", "ceiling tile", "furring channel", "top cross rail" ], "exactness": "close", "note": "FURRING CHANNEL names the concealed framing member, so the Australian vocabulary follows the component rather than the British initialism." }, { "market": "US", "term": "drop ceiling", "alsoCalled": [ "suspended ceiling", "ACT", "acoustical ceiling tile", "T-bar", "grid", "plenum" ], "exactness": "close", "note": "DROP CEILING is the common term and ACT the specification word. PLENUM here is often a fire and air-handling classification with its own material rules, not just the void." }, { "market": "CA", "term": "drop ceiling", "alsoCalled": [ "T-bar ceiling", "ACT", "suspended ceiling", "plenum rated" ], "exactness": "close", "note": "As the United States, with PLENUM RATED a purchasing requirement for cabling and components in the void wherever it is used to return air." } ], "standards": [ { "market": "UK", "standard": "BS EN 13964 / BS 8290 legacy", "covers": "Suspended ceilings including requirements and test methods for the grid and infill, and the historic British code of practice for their design." }, { "market": "US", "standard": "ASTM C635 / ASTM C636", "covers": "Manufacture, performance and testing of metal suspension systems for acoustical tile, and the practice for their installation including seismic considerations." } ], "calculators": [ { "slug": "suspended-ceiling-wire-hanger-calculator", "json": "https://craftquantities.com/api/v1/calculators/suspended-ceiling-wire-hanger-calculator.json" }, { "slug": "acoustic-ceiling-cloud-wire-calculator", "json": "https://craftquantities.com/api/v1/calculators/acoustic-ceiling-cloud-wire-calculator.json" }, { "slug": "ceiling-control-joint-calculator", "json": "https://craftquantities.com/api/v1/calculators/ceiling-control-joint-calculator.json" } ], "confusions": [ { "question": "Why is the void above a ceiling a fire and air question, not just a gap?", "answer": "Because it is continuous, and anything continuous through a building is a route. A ceiling void usually runs uninterrupted above the partitions below it, so a fire starting in one room passes over the partition heads into every other room the void reaches — which is why cavity barriers are required in the void on the line of any wall that is meant to be a fire or smoke barrier, and why a partition built only up to the ceiling grid provides neither fire separation nor the acoustic separation people assume it does. In North America there is a second layer: where the void is used to RETURN air to the plant, it is a plenum, and everything in it — cabling, insulation, pipe lagging — has to meet a smoke and flame-spread rating, because the air in that space goes back into the occupied building. That is why plenum-rated cable costs several times the ordinary kind and why substituting it is a code matter rather than a saving." }, { "question": "What actually decides whether a partition stops sound?", "answer": "Whether it goes past the ceiling, in nearly every case where a room is disappointing. A partition built to the underside of a suspended ceiling leaves the void as an open path over the top, and sound takes it: the flanking route over the partition head bypasses the wall entirely, so a wall specified at a high sound reduction performs like the ceiling tiles and the void. The fixes, in order of effectiveness, are to take the partition up to the structural soffit and seal it, or to fit a barrier in the void on the line of the wall, or — least effective and most commonly attempted — to lay heavy pads over the tiles either side. This is the same flanking principle the sound-rating concept describes, and the ceiling void is where it bites most often, because the partition looks complete from the room." }, { "question": "Why are the hanger and grid spacings not just a matter of holding the weight?", "answer": "Because the failures they prevent are stiffness and movement rather than collapse. The dead load of a tile grid is small; what the spacing controls is DEFLECTION — a main runner spanning too far between hangers sags visibly against a straight line of light from a window, and the eye is very good at seeing that. Spacing also governs what the ceiling can carry as point loads: a light fitting, a diffuser or a projector mount is not a tile's job, and each needs its own independent hangers rather than sitting in the grid. And in seismic regions the rules are different again, because a ceiling that is merely hung swings: bracing wires and a perimeter detail that allows movement without the grid walking off its wall angle are required, which is why the American installation standard has a separate seismic section rather than a note. A grid installed to a European layout in a seismic zone is a life-safety issue rather than a finishing one." } ], "related": [ "dry-lining" ] }, { "slug": "textured-coating", "concept": "Textured coating", "family": "finishes", "definition": "A thick decorative finish applied to a ceiling or wall and worked into a pattern while wet, rather than a paint. Common from the 1960s to the 1980s and frequently overcoated since.", "url": "https://craftquantities.com/glossary/textured-coating/", "names": [ { "market": "UK", "term": "Artex", "alsoCalled": [ "textured coating", "stipple", "swirl ceiling", "textured finish" ], "exactness": "false-friend", "note": "ARTEX is a trademark used generically for any textured ceiling finish, including coatings that brand never made — so the word says nothing about what a particular ceiling contains." }, { "market": "AU", "term": "textured ceiling", "alsoCalled": [ "stipple ceiling", "vermiculite ceiling", "acoustic ceiling spray" ], "exactness": "close", "note": "VERMICULITE naming is common here and is worth noting separately, because vermiculite from some sources carried asbestos contamination independently of any added to the mix." }, { "market": "US", "term": "popcorn ceiling", "alsoCalled": [ "acoustic ceiling", "cottage cheese ceiling", "stipple", "knockdown", "orange peel" ], "exactness": "false-friend", "note": "ACOUSTIC CEILING here means this sprayed finish, not a suspended acoustic tile ceiling — two different products sharing a name in the same market." }, { "market": "CA", "term": "stipple ceiling", "alsoCalled": [ "popcorn ceiling", "textured ceiling", "stucco ceiling" ], "exactness": "false-friend", "note": "STUCCO CEILING is used for the interior sprayed finish, which is unrelated to the exterior cement render that stucco means everywhere else." } ], "standards": [ { "market": "UK", "standard": "Control of Asbestos Regulations 2012 / HSG264", "covers": "Duties where work may disturb asbestos-containing materials, and the survey guide that covers textured coatings as a distinct material type." }, { "market": "US", "standard": "40 CFR 61 Subpart M / 29 CFR 1926.1101", "covers": "The asbestos emission standard and its friable classification, and the construction standard's exposure classes for removal of surfacing material." } ], "calculators": [ { "slug": "drywall-texture-coverage-calculator", "json": "https://craftquantities.com/api/v1/calculators/drywall-texture-coverage-calculator.json" }, { "slug": "ceiling-plasterboard-sheet-calculator", "json": "https://craftquantities.com/api/v1/calculators/ceiling-plasterboard-sheet-calculator.json" } ], "confusions": [ { "question": "Does a textured ceiling mean asbestos?", "answer": "It means the question has to be asked rather than answered by eye, and the honest position is that nothing about the appearance settles it. Textured coatings of the relevant era commonly contained a small percentage of chrysotile as a reinforcing fibre; later ones do not; and the two look identical, take the same patterns, and were sold under the same brand names through the transition. Age is a weak guide because a ceiling can have been recoated at any point, and a newer surface can sit directly on an older one. So the reliable route is a sample tested by a laboratory, taken by somebody competent to take it without releasing fibres. What the percentage means in practice is also worth knowing: the content is usually low and the material is bound, so an intact coating is a low-risk material to LEAVE, and the hazard is created entirely by how it is removed." }, { "question": "Why is scraping it off worse than covering it up?", "answer": "Because removal is the step that turns a bound material into airborne dust, and the alternatives avoid that step entirely. Dry scraping and — worst of all — power sanding a textured coating generate fine dust at exactly the moment a person is standing under it with their face upward. The two low-disturbance answers are to OVERBOARD, fixing plasterboard through the coating into the joists and skimming that, which leaves the original sealed behind a new surface; or to skim over it after a bonding treatment, where the texture is shallow enough. Where removal is genuinely necessary, the methods that keep the dust down are steam or a wetting agent that softens the coating so it comes away in wet lumps rather than dust, under controlled conditions. It is the same logic the asbestos concept sets out generally: manage and encapsulate by default, remove only when something requires it, and never with a tool that makes powder." }, { "question": "Why is it called an acoustic ceiling in the United States?", "answer": "Because that was the selling point, and the name stuck to the product rather than to the performance. A sprayed textured finish has a large, irregular surface area and an open structure, which absorbs a measurable amount of sound in a room — modestly, but noticeably compared with flat plaster — and it was marketed on that as well as on hiding imperfect jointing and needing no further decoration. The result is a genuine ambiguity inside one market: ACOUSTIC CEILING can mean this sprayed coating or a suspended grid of acoustic tiles, which are different trades, different costs and different orders of magnitude of sound absorption. Context usually resolves it — a grid ceiling is described by its tiles and its runners — but a specification line reading *remove existing acoustic ceiling* has been read both ways on real jobs, and the two readings differ by whether an asbestos survey is required first." } ], "related": [ "asbestos" ] }, { "slug": "curtain-wall", "concept": "Curtain wall", "family": "envelope", "definition": "A building envelope hung from the structural frame, carrying only its own weight and wind load. Usually a grid of mullions and transoms infilled with glass or opaque panels.", "url": "https://craftquantities.com/glossary/curtain-wall/", "names": [ { "market": "UK", "term": "curtain walling", "alsoCalled": [ "curtain wall", "stick system", "unitised", "mullion", "transom", "spandrel panel" ], "exactness": "close", "note": "CURTAIN WALLING is the usual British form of the noun. SPANDREL PANEL names the opaque section hiding the floor slab, which is a fire and thermal detail as much as a visual one." }, { "market": "AU", "term": "curtain wall", "alsoCalled": [ "curtain walling", "unitised facade", "stick system", "shopfront" ], "exactness": "false-friend", "note": "SHOPFRONT is used for the ground-level glazed systems that look similar and are engineered quite differently — lower spans, different loads, and not a curtain wall." }, { "market": "US", "term": "curtain wall", "alsoCalled": [ "stick-built curtain wall", "unitized", "storefront", "rainscreen", "pressure-equalized" ], "exactness": "false-friend", "note": "STOREFRONT is a distinct product class — shallower framing for low-rise glazing — and is not a curtain wall despite looking like one from the pavement." }, { "market": "CA", "term": "curtain wall", "alsoCalled": [ "unitized curtain wall", "window wall", "storefront", "thermally broken" ], "exactness": "false-friend", "note": "WINDOW WALL is a separate system that sits BETWEEN floor slabs rather than passing in front of them, common in Canadian residential towers and frequently mislabelled as curtain wall." } ], "standards": [ { "market": "UK", "standard": "BS EN 13830 / CWCT Standard", "covers": "Curtain walling as a product standard covering performance characteristics, and the Centre for Window and Cladding Technology's standard for systemised building envelopes." }, { "market": "US", "standard": "AAMA 501 / ASTM E1105", "covers": "Methods of test for exterior walls including field water penetration, and the standard test for water penetration under uniform or cyclic static air pressure." } ], "calculators": [ { "slug": "curtain-wall-mullion-load-calculator", "json": "https://craftquantities.com/api/v1/calculators/curtain-wall-mullion-load-calculator.json" }, { "slug": "curtain-wall-panel-count-calculator", "json": "https://craftquantities.com/api/v1/calculators/curtain-wall-panel-count-calculator.json" }, { "slug": "curtain-wall-anchor-bracket-calculator", "json": "https://craftquantities.com/api/v1/calculators/curtain-wall-anchor-bracket-calculator.json" }, { "slug": "ssg-bite-width-calculator", "json": "https://craftquantities.com/api/v1/calculators/ssg-bite-width-calculator.json" }, { "slug": "mullion-deflection-calculator", "json": "https://craftquantities.com/api/v1/calculators/mullion-deflection-calculator.json" }, { "slug": "mullion-stack-joint-gap-calculator", "json": "https://craftquantities.com/api/v1/calculators/mullion-stack-joint-gap-calculator.json" } ], "confusions": [ { "question": "What is the difference between stick and unitised?", "answer": "Where the assembly happens, and it changes the programme, the tolerance regime and the cost base. A STICK system arrives as components — mullions, transoms, gaskets, glass — and is built up in place on the building, working off a scaffold or a mast climber. It is cheaper in material, forgiving of an irregular building, and slow, weather-dependent and dependent on site workmanship for the seals that keep water out. A UNITISED system arrives as completed storey-height panels made in a factory, lifted into place and hooked onto brackets, with the joints between units designed as split mullions that engage as each panel lands. It is faster on site, needs no external access, and is far more consistent because the sealing is done in a controlled environment — at the cost of a long lead time, a large factory order committed early, and tolerances at the brackets that the structure has to actually meet. Tall buildings go unitised for the programme; irregular and low-rise ones stay stick." }, { "question": "How does a pressure-equalised joint keep water out without a seal?", "answer": "By removing the force that drives water through a gap rather than by closing the gap. Water crosses a joint when three things coincide: water at the opening, a gap for it to pass, and a pressure difference pushing it. Sealing everything attacks the second and is fragile — one failed bead, one shrinkage crack, and the water is inside with nothing to stop it. A pressure-equalised design attacks the third instead: the outer face is deliberately open, a chamber behind it is vented to the outside so the air pressure inside the joint matches the wind pressure outside, and the airtight line is set well back at the inner face. With no pressure difference across the outer opening, water has nothing pushing it inward; the little that enters by gravity or momentum runs down internal gutters and out through weep holes at the transoms. The consequences on site are the ones that surprise people: weep holes must never be sealed, water appearing inside the frame may be the system working, and a repair that simply caps the outer joint with sealant converts a drained wall into a trap." }, { "question": "Why is the movement joint at the slab the detail that decides everything?", "answer": "Because the wall and the building move differently and the brackets have to allow it without letting the facade carry load. The frame shortens elastically as floors are added, concrete creeps and shrinks for years, floors deflect under their own imposed loads, and the whole building sways in wind — while the curtain wall expands and contracts with temperature on an entirely different cycle. If the connections do not permit that relative movement, the facade starts to carry load it was never designed for: glass goes into compression and cracks, gaskets roll out of their channels, and the joints between units close up until they bind. So the brackets are slotted in the directions movement is expected and fixed in the direction load is transferred, and the joint width between units is a calculated figure rather than a constructional gap. It is also the reason a curtain wall cannot simply be surveyed once at design stage: the structure's tolerances at every bracket are the input, and discovering them after fabrication is the expensive order of events." } ], "related": [ "cladding" ] }, { "slug": "ice-dam", "concept": "Ice dam", "family": "envelope", "definition": "A ridge of ice at a roof's eaves, formed when snow melted by heat escaping through the roof refreezes over the cold overhang, ponding water behind it and driving it back under the covering.", "url": "https://craftquantities.com/glossary/ice-dam/", "names": [ { "market": "UK", "term": "ice dam", "alsoCalled": [ "ice damming", "snow melt", "ice build-up" ], "exactness": "absent", "note": "No established British term and no standard detail against it, because prolonged sub-zero spells with lying snow are uncommon. The phenomenon occurs occasionally; the vocabulary does not exist." }, { "market": "AU", "term": "ice dam", "alsoCalled": [ "alpine roofing", "snow load" ], "exactness": "absent", "note": "Confined to alpine areas, where specialist roofing practice covers it. In the housing the rest of the country builds there is no equivalent term and no detail." }, { "market": "US", "term": "ice dam", "alsoCalled": [ "ice barrier", "ice and water shield", "eave membrane", "self-adhering underlayment" ], "exactness": "identical", "note": null }, { "market": "CA", "term": "ice dam", "alsoCalled": [ "ice damming", "eave protection", "ice and water shield", "eave membrane" ], "exactness": "close", "note": "EAVE PROTECTION is the code's own term for the membrane, so the Canadian requirement is written as a protection rather than named after the failure it prevents." } ], "standards": [ { "market": "US", "standard": "IRC R905.1.2 / ASTM D1970", "covers": "Ice barrier requirements in regions with a history of ice forming along eaves, and the specification for self-adhering polymer modified bituminous sheet used as an underlayment." }, { "market": "CA", "standard": "NBC 9.26.5 / CSA A123.22", "covers": "Eave protection requirements for shingle roofs, and self-adhering polymer modified bituminous sheet materials used for that purpose." } ], "calculators": [ { "slug": "roof-ice-dam-membrane-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-ice-dam-membrane-calculator.json" }, { "slug": "ice-water-shield-calculator", "json": "https://craftquantities.com/api/v1/calculators/ice-water-shield-calculator.json" }, { "slug": "roof-snow-load-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-snow-load-calculator.json" } ], "confusions": [ { "question": "Why does an ice dam form at the eaves and not on the rest of the roof?", "answer": "Because the eaves are the only part of the roof with nothing warm under them. Heat escaping from the house into the loft warms the underside of the roof deck over the heated rooms, and snow lying on that part melts from below even while the air stays well below freezing. The meltwater runs down the slope until it crosses the wall line and reaches the OVERHANG, which has outside air both above and below it and is therefore at air temperature. There it refreezes, and the ice that accumulates dams the water still arriving from above. Ponded water sits behind the dam, finds the laps in the covering — which shed water flowing downhill and are not designed to hold standing water — and runs back under them into the structure. The damage shows as stains on the ceiling at the outside wall, which is why an ice dam is so often diagnosed as a roof leak and repaired by replacing shingles that were never faulty." }, { "question": "Is the membrane the fix?", "answer": "It is the insurance, not the cure, and the distinction matters because the membrane is the part people buy. A self-adhering ice barrier laid from the eaves up past the wall line seals around the fixings through it and keeps ponded water out of the structure when a dam forms. What it does not do is stop the dam forming, and a roof that keeps forming them still loses heat, still grows ice on the overhang, and still drops that ice on whatever is below. The actual cure is to stop the heat reaching the deck: air-seal the ceiling so warm air is not leaking into the loft, insulate it to the depth the climate needs, and ventilate the loft so that the deck runs close to outside temperature. The membrane and the heat control are not alternatives — codes require the membrane because heat control is imperfect in practice — but a specification that provides only the membrane has treated the symptom." }, { "question": "What does a British roof do instead?", "answer": "Nothing, and mostly it does not need to — which is the point worth carrying across. The British detail at an eaves is an underlay carried into the gutter over a support tray, designed to drain any water that gets past the tiles back OUT, and a ventilated or breathable roof build-up behind it. It assumes water flows; it does not assume water stands. That assumption holds where sustained freezing with snow cover is rare, and stops holding in a hard winter, when the same houses do produce ice at the gutter and occasional leaks at the wall head. The practical consequences run both ways. An American or Canadian detail applied in Britain adds a self-adhering membrane that is rarely required and can trap moisture in a construction designed to breathe. A British detail applied in a cold-winter climate omits a code requirement — which is the more serious direction, because a missing eave membrane is invisible until the first thaw." } ], "related": [ "eaves", "snow-load" ] }, { "slug": "pipe-insulation", "concept": "Pipe insulation", "family": "services", "definition": "Insulation around a pipe or a vessel, to stop heat leaving a hot service, to stop heat reaching a cold one, or to stop a pipe freezing. Different jobs with different correct thicknesses.", "url": "https://craftquantities.com/glossary/pipe-insulation/", "names": [ { "market": "UK", "term": "lagging", "alsoCalled": [ "pipe insulation", "cylinder jacket", "pipe wrap", "trace heating" ], "exactness": "false-friend", "note": "LAGGING is also the word for the asbestos pipe insulation used until the 1980s, which is friable and among the most hazardous materials to disturb. Age, not appearance, decides which is meant." }, { "market": "AU", "term": "pipe lagging", "alsoCalled": [ "pipe insulation", "closed cell", "cylinder blanket" ], "exactness": "close", "note": "Carries the same historic asbestos sense, with the added local point that insulating a cold-water pipe against condensation matters more than insulating it against freezing." }, { "market": "US", "term": "pipe insulation", "alsoCalled": [ "pipe wrap", "pipe lagging", "heat tape", "armaflex", "fiberglass pipe cover" ], "exactness": "false-friend", "note": "HEAT TAPE means an electrical trace-heating cable, not a tape and not insulation — and it is fitted UNDER the insulation, so the two are specified together and confused often." }, { "market": "CA", "term": "pipe insulation", "alsoCalled": [ "pipe wrap", "heat trace", "heat tape", "foam sleeve" ], "exactness": "close", "note": "Freeze protection rather than energy saving is usually the driver, so the specification is about keeping a pipe above zero rather than about keeping heat in it." } ], "standards": [ { "market": "UK", "standard": "BS 5422 / Approved Document L", "covers": "Method for specifying thermal insulating materials for pipes and ductwork, and the requirement to insulate primary circulation pipework." }, { "market": "US", "standard": "ASTM C547 / ASHRAE 90.1", "covers": "Mineral fiber pipe insulation including temperature limits, and the minimum pipe insulation thickness tables by fluid temperature and pipe size." } ], "calculators": [ { "slug": "pipe-insulation-calculator", "json": "https://craftquantities.com/api/v1/calculators/pipe-insulation-calculator.json" }, { "slug": "duct-insulation-wrap-calculator", "json": "https://craftquantities.com/api/v1/calculators/duct-insulation-wrap-calculator.json" }, { "slug": "refrigerant-line-equivalent-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/refrigerant-line-equivalent-length-calculator.json" }, { "slug": "trapeze-hanger-rod-sizing-calculator", "json": "https://craftquantities.com/api/v1/calculators/trapeze-hanger-rod-sizing-calculator.json" } ], "confusions": [ { "question": "Why does insulating a cold pipe need a vapour seal when a hot one does not?", "answer": "Because the moisture is moving the other way, and insulation that gets wet stops insulating. On a HOT pipe, vapour pressure inside the insulation is higher than outside, so any moisture is driven out and the insulation stays dry on its own. On a COLD pipe the gradient reverses: warm room air carries vapour toward a surface below its dew point, and the condensation forms INSIDE the insulation against the pipe, where it cannot evaporate. Wet insulation loses most of its performance, the pipe then runs colder, more condenses, and the material rots or corrodes the pipe under it. So cold-service insulation is specified with a continuous vapour barrier on its OUTER face and with every joint, fitting and support sealed — a single unsealed butt joint provides a path for the whole run. This is the reason closed-cell elastomeric is the default on chilled and cold services, and the reason fibrous insulation is a poor choice there however thick it is." }, { "question": "Is more thickness always better?", "answer": "No, and on a small pipe it can genuinely be worse. Adding insulation increases the thermal resistance of the path out, but it also increases the OUTER surface area losing heat to the air. On a large pipe the first effect dominates from the start. On a small one — a thin copper pipe, a cable — the second can dominate at small thicknesses, so heat loss rises with the first few millimetres and only starts falling once the insulation passes what is called the critical radius. The practical reach of this is limited, because the critical radius for the low-conductivity materials and the pipe sizes used in buildings is usually small enough that any commercial thickness is past it — but it explains why specification tables give thickness against pipe DIAMETER rather than one figure, why the thickness rises with the pipe size, and why the answer is a lookup rather than an intuition. For freeze protection, thickness buys TIME rather than prevention: an unheated pipe in a cold void eventually reaches air temperature whatever it is wrapped in, so trace heating rather than more insulation is the answer where the pipe must not freeze." }, { "question": "Why is old lagging treated so seriously?", "answer": "Because it is the friable end of the asbestos range, and friability is what decides risk. Pipe and boiler insulation was made by mixing asbestos into a soft, porous matrix — a moulded section, a bandage, or a plaster applied wet — precisely because that structure traps air and insulates well. That same structure means the fibres are barely bound: brushing past damaged lagging, sweeping up debris under it, or pulling a pipe out of it releases fibres readily, where an asbestos cement sheet in the same building would release almost none. That is why removal of pipe lagging sits in the licensed category in British law, why the material appears prominently in survey guidance, and why the advice for anyone finding damaged insulation on old pipework is to stop, not to tidy. It is also why the word matters: an instruction to strip the old lagging off a heating system is either a morning's work or a licensed contractor with an enclosure, and the age of the installation is what separates them." } ], "related": [ "hot-water-cylinder" ] }, { "slug": "bulking", "concept": "Bulking and swell", "family": "site", "definition": "The increase in volume when ground is excavated, because digging replaces a settled structure with a loose heap full of voids. The same material compacted back occupies less than the heap and often less than the hole.", "url": "https://craftquantities.com/glossary/bulking/", "names": [ { "market": "UK", "term": "bulking", "alsoCalled": [ "bulking factor", "bulkage", "loose volume", "bank volume", "compacted volume" ], "exactness": "false-friend", "note": "BULKING of SAND is a different phenomenon with the same word — damp sand expanding because of surface moisture, which matters when batching concrete by volume rather than when digging." }, { "market": "AU", "term": "bulking", "alsoCalled": [ "swell", "bulking factor", "loose cubic metres", "compacted cubic metres" ], "exactness": "close", "note": "Both terms in use, with quantities commonly qualified as LOOSE or COMPACTED cubic metres so the state is stated rather than assumed." }, { "market": "US", "term": "swell", "alsoCalled": [ "swell factor", "bank cubic yards", "BCY", "loose cubic yards", "LCY", "compacted cubic yards", "CCY", "shrinkage" ], "exactness": "false-friend", "note": "Three separate units — BANK, LOOSE and COMPACTED cubic yards — and a quantity without one of those three letters is ambiguous. SHRINKAGE names the compaction factor, not a loss of material." }, { "market": "CA", "term": "swell", "alsoCalled": [ "bank cubic metres", "loose cubic metres", "shrinkage factor", "compaction factor" ], "exactness": "close", "note": "As the United States with metric units, so BCM and LCM replace BCY and LCY and the same three-state distinction applies." } ], "standards": [ { "market": "UK", "standard": "CIRIA C750 / BS 6031", "covers": "Groundwater control and earthworks guidance including volume change on excavation, and the code of practice for earthworks covering fill and compaction." }, { "market": "US", "standard": "AASHTO T 180 / Caterpillar Performance Handbook", "covers": "Moisture-density relations of soils used to define compacted density, and the industry reference tables for swell and shrinkage by material type." } ], "calculators": [ { "slug": "soil-swell-shrinkage-calculator", "json": "https://craftquantities.com/api/v1/calculators/soil-swell-shrinkage-calculator.json" }, { "slug": "demolition-bulk-volume-swell-calculator", "json": "https://craftquantities.com/api/v1/calculators/demolition-bulk-volume-swell-calculator.json" }, { "slug": "cut-fill-earthwork-balance-calculator", "json": "https://craftquantities.com/api/v1/calculators/cut-fill-earthwork-balance-calculator.json" }, { "slug": "material-weight-calculator", "json": "https://craftquantities.com/api/v1/calculators/material-weight-calculator.json" } ], "confusions": [ { "question": "Why is there more spoil than hole?", "answer": "Because undisturbed ground is a settled structure and a heap is not. In the bank, particles have been packed by centuries of overburden and water into an arrangement with comparatively few voids. Digging breaks that arrangement apart: the same solids are now loosely piled with air between them, so the volume goes up — modestly for sand, which was already loose, and substantially for stiff clay or rock, which was tightly bound and breaks into lumps that cannot repack themselves. Typical figures run from a small percentage for sand up to half as much again for clay and more for blasted rock. The consequence for a job is entirely practical: excavation is measured in the BANK, because that is the hole being dug, but everything that leaves site — lorry loads, skip counts, tip charges — is measured LOOSE. Ordering disposal from the excavation quantity under-orders it by the bulking factor every time." }, { "question": "If it bulks when dug, why does backfill run short?", "answer": "Because two different changes happen in sequence and only the first is an expansion. Digging loosens the material, and compacting it puts it back into a dense arrangement — but the machine and the layer thickness do a better job than the original geology did in some soils and a worse one in others, so the compacted volume can be less than the bank volume it came from. That second change is what American usage calls SHRINKAGE, and it is measured from bank to compacted while swell is measured from bank to loose. Nothing has been lost: the same solids occupy less space because there is less air between them. This is the arithmetic behind the routine surprise on a cut-and-fill exercise, where a balanced cut and fill on the drawing needs imported material on site. Anyone reconciling earthworks has to carry three volumes rather than one, and to say which of the three any figure is." }, { "question": "Is bulking of sand the same thing?", "answer": "No, and the shared word causes real errors in concrete. BULKING OF SAND is a surface-tension effect: a film of moisture on damp sand grains holds them apart, and sand at a few percent moisture can occupy a quarter more volume than the same dry sand — with the expansion peaking at a moderate moisture content and collapsing again once the sand is saturated, because water then fills the voids instead of separating the grains. It has nothing to do with excavation and everything to do with batching. Measuring aggregate by VOLUME from a damp stockpile therefore puts materially less sand into a mix than the proportion intended, which weakens it, and the effect is largest exactly where site sand is normally kept: damp, uncovered, part-used. It is the main reason concrete specifications are written by mass rather than by volume, and why a site-batched mix from a shovel count is not the mix on the drawing." } ], "related": [ "skip" ] }, { "slug": "trench-support", "concept": "Trench support", "family": "site", "definition": "What stops the sides of an excavation coming in: battering them back to a safe angle, holding them with a supporting frame, or placing a box in the trench that protects the people rather than the ground.", "url": "https://craftquantities.com/glossary/trench-support/", "names": [ { "market": "UK", "term": "trench support", "alsoCalled": [ "timbering", "shoring", "trench box", "drag box", "battering", "hydraulic waler" ], "exactness": "false-friend", "note": "TIMBERING survives as the generic word for supporting an excavation even where no timber is involved. BATTERING is cutting the sides back, which is support by geometry rather than by equipment." }, { "market": "AU", "term": "shoring", "alsoCalled": [ "trench shield", "benching", "battering", "trench box", "ground support" ], "exactness": "close", "note": "BENCHING — cutting the sides into steps rather than one continuous slope — is named separately here and in American practice, and is not a British term." }, { "market": "US", "term": "protective system", "alsoCalled": [ "trench box", "trench shield", "shoring", "sloping", "benching", "competent person" ], "exactness": "false-friend", "note": "PROTECTIVE SYSTEM is the regulatory umbrella covering three named options. SHIELDING with a box does NOT support the ground — it protects people inside it while the ground does whatever it will." }, { "market": "CA", "term": "shoring", "alsoCalled": [ "trench box", "trench cage", "sloping", "soil type classification" ], "exactness": "close", "note": "Requirements are provincial and keyed to a soil TYPE classification, so the same trench in the same ground can require different measures across a provincial boundary." } ], "standards": [ { "market": "UK", "standard": "CDM 2015 / HSG185", "covers": "Construction design and management duties including excavations, and the health and safety guidance on health and safety in excavations." }, { "market": "US", "standard": "29 CFR 1926 Subpart P", "covers": "Excavations, including soil classification, the requirement for a protective system beyond a stated depth, and the competent person's inspection duties." } ], "calculators": [ { "slug": "trench-safety-slope-calculator", "json": "https://craftquantities.com/api/v1/calculators/trench-safety-slope-calculator.json" }, { "slug": "excavation-sloping-setback-calculator", "json": "https://craftquantities.com/api/v1/calculators/excavation-sloping-setback-calculator.json" }, { "slug": "shoring-active-pressure-calculator", "json": "https://craftquantities.com/api/v1/calculators/shoring-active-pressure-calculator.json" }, { "slug": "soil-relative-density-calculator", "json": "https://craftquantities.com/api/v1/calculators/soil-relative-density-calculator.json" }, { "slug": "spt-overburden-correction-calculator", "json": "https://craftquantities.com/api/v1/calculators/spt-overburden-correction-calculator.json" } ], "confusions": [ { "question": "Does a trench box hold the ground up?", "answer": "No, and that is the most consequential misunderstanding about it. A trench box — a shield, a drag box — is two side panels held apart by struts, placed in the trench so that people work inside it. It is designed to withstand a collapse, not to prevent one: the ground outside can move, and the box's job is that the people inside are not in the way when it does. SHORING is the different thing that does prevent it, holding the faces in place with hydraulic props or sheets pressed against the ground so the soil never moves at all. The practical distinctions follow directly. A box protects only the space inside it, so working outside the box in an unsupported length is unprotected regardless of the box being there. A box does not stop ground movement, so it gives no protection to a service, a road or a neighbouring foundation beside the trench. And a box is dragged along as work proceeds, which is what makes it fast and what makes the unprotected moment while it moves worth planning for." }, { "question": "Why does the required slope depend on the soil rather than the depth?", "answer": "Because what fails is the ground's ability to stand at an angle, and that is a property of the material. Cohesive clay can stand near vertical for a while; granular sand cannot stand much steeper than its angle of repose at all; and previously excavated ground — a backfilled service trench, made ground, anything that has been disturbed — behaves worse than either, because its structure was destroyed once already. So classification comes first and the permitted slope follows from it, which is why American regulation defines soil types with field and laboratory tests and publishes a maximum slope for each. Three factors make real ground worse than its classification suggests, and all three are visible on site: WATER, which removes apparent cohesion and adds weight; VIBRATION from plant or traffic alongside; and SURCHARGE, which is anything stacked near the edge — spoil, materials, a parked machine. Spoil heaped at the lip of a trench is the commonest of these and the easiest to move." }, { "question": "What makes a shallow trench dangerous?", "answer": "The weight, and the fact that a person buried to the waist cannot get out or be pulled out. A cubic metre of soil weighs somewhere over a tonne and a half; a collapse does not need to cover someone to kill them, because the pressure on the chest of material up to waist height is enough to stop breathing, and the victim is held in place by friction against their whole lower body. Rescue then takes far longer than the time available, and attempting it without supporting the trench has killed rescuers repeatedly, which is why regulations require support well below the depth at which people intuitively start worrying. Two further properties make it worse than it looks: collapses are sudden and give no useful warning, and a trench that has stood open safely for days can fail after rain, after a machine passes, or as the ground dries and cracks. Time standing open is not evidence of stability, which is why inspection is required at the start of every shift rather than once at the start of the job." } ], "related": [ "acrow-prop" ] }, { "slug": "impact-sound", "concept": "Impact sound insulation", "family": "finishes", "definition": "How much footfall, dropped objects and furniture movement on a floor are heard in the room below. Measured with a standard tapping machine, and rated on scales that run in opposite directions.", "url": "https://craftquantities.com/glossary/impact-sound/", "names": [ { "market": "UK", "term": "impact sound", "alsoCalled": [ "Ln,w", "L'nT,w", "impact sound pressure level", "acoustic underlay", "resilient layer" ], "exactness": "false-friend", "note": "Ln,w is a NOISE level, so a LOWER number is a better floor — the opposite direction to the airborne Rw on the same test certificate, and to the American IIC." }, { "market": "AU", "term": "impact sound", "alsoCalled": [ "Ln,w", "LnT,w", "AAAC star rating", "resilient underlay" ], "exactness": "close", "note": "Uses the European Ln,w family, with a voluntary star rating alongside it that runs the other way — more stars is better, fewer decibels is better, on the same floor." }, { "market": "US", "term": "IIC", "alsoCalled": [ "impact insulation class", "FIIC", "field IIC", "sound mat", "delta IIC" ], "exactness": "false-friend", "note": "IIC is an INSULATION class, so a HIGHER number is better. DELTA IIC rates the improvement an underlay adds, not the floor — the two are quoted in the same sales literature." }, { "market": "CA", "term": "IIC", "alsoCalled": [ "ASTC", "apparent sound transmission class", "impact insulation class", "FIIC" ], "exactness": "false-friend", "note": "The national code moved to APPARENT ratings, which include flanking transmission — so a Canadian ASTC figure is always lower than the laboratory number for the same assembly." } ], "standards": [ { "market": "UK", "standard": "Approved Document E / BS EN ISO 717-2", "covers": "Resistance to the passage of sound including the pre-completion testing regime, and the rating of impact sound insulation in buildings." }, { "market": "US", "standard": "ASTM E492 / ASTM E1007", "covers": "Laboratory measurement of impact sound transmission using the tapping machine, and the field measurement of impact sound transmission through floor-ceiling assemblies." } ], "calculators": [ { "slug": "floor-underlayment-roll-calculator", "json": "https://craftquantities.com/api/v1/calculators/floor-underlayment-roll-calculator.json" }, { "slug": "self-leveling-underlayment-calculator", "json": "https://craftquantities.com/api/v1/calculators/self-leveling-underlayment-calculator.json" } ], "confusions": [ { "question": "Why does a better floor have a lower number in one market and a higher one in the other?", "answer": "Because the two scales measure different quantities that happen to be about the same thing. Ln,w is a SOUND PRESSURE LEVEL: the machine taps, a microphone in the room below records how loud it is, and the rating is that loudness — so quieter is better and the number falls as the floor improves. IIC is an INSULATION CLASS: it is derived from the same measurement but expressed as how much the assembly reduces the noise, so more insulation is better and the number rises. They are not convertible by a fixed offset either, because they weight the frequency bands differently and reference different curves, though a rough rule of thumb circulates that adding the two gives a roughly constant figure for typical floors. The practical rule is the safe one: never compare a bare number, always carry the letters, and treat any specification that mixes the two scales as unverified until each figure is matched to its own standard." }, { "question": "Why does a hard floor covering ruin an acoustic floor that tested well?", "answer": "Because the test result belongs to the whole build-up including its finish, and impact sound is created at the SURFACE. Airborne sound has to get through the mass of the floor, so the covering barely matters; impact sound starts when a heel or a dropped mug strikes the top layer, and a soft covering absorbs much of that energy before it ever enters the structure. Carpet on underlay is, in impact terms, an enormously effective treatment — which is why a floor that performed well in a carpeted flat can fail outright when the occupant replaces it with engineered wood or tile. That is the reason leases in apartment buildings so often specify floor coverings, why a resilient layer under a hard floor is a structural part of the specification rather than a comfort item, and why an impact rating quoted without naming the finish that was on the floor during the test says almost nothing." }, { "question": "What is flanking, and why is the field number always worse?", "answer": "Flanking is every path the sound takes that does not go straight through the element being rated — around it through the walls, along a continuous screed, down a rigid skirting, through a shared joist that is built into both parties' walls. A laboratory test deliberately removes those paths, so a laboratory rating describes the floor in isolation and nothing else. In a real building the paths exist, so the measured performance is always lower, which is why the field and apparent ratings carry their own letters: FIIC in the United States, ASTC in Canada, the primed L'nT,w in Britain. The practical consequence is the same one the airborne sound concept records: a floor built exactly to a laboratory specification can still fail a completion test, because the failure is at the junctions. Isolating the resilient layer at its perimeter — turning it up the wall so the screed never touches the structure — is the detail that most often decides it." } ], "related": [ "sound-rating" ] }, { "slug": "tile-adhesive", "concept": "Tile adhesive", "family": "finishes", "definition": "What holds a tile to its background. A cement-based mortar in almost all modern work, notched onto the substrate to a depth that suits the tile's size and flatness.", "url": "https://craftquantities.com/glossary/tile-adhesive/", "names": [ { "market": "UK", "term": "tile adhesive", "alsoCalled": [ "adhesive", "cement-based adhesive", "rapid set", "ready mixed", "notched trowel", "S1 flexible" ], "exactness": "false-friend", "note": "READY MIXED is a paste adhesive that dries rather than sets, and is limited to small wall tiles in dry areas — a different product from the cement powder most jobs need." }, { "market": "AU", "term": "tile adhesive", "alsoCalled": [ "cement based adhesive", "C2 adhesive", "flexible adhesive", "notched trowel" ], "exactness": "close", "note": "Classified by the same European C and S codes as British practice, so a C2S1 here means what it means there, which is unusual on this site." }, { "market": "US", "term": "thinset", "alsoCalled": [ "thinset mortar", "thin-set", "mastic", "modified thinset", "medium bed", "LFT" ], "exactness": "false-friend", "note": "MASTIC here is the organic paste adhesive, the counterpart of British ready-mixed — so the American word for the lesser product is the British word for sealant." }, { "market": "CA", "term": "thinset", "alsoCalled": [ "thin-set mortar", "mastic", "modified mortar", "large format mortar" ], "exactness": "close", "note": "As the United States, with the modified and unmodified distinction sharpened by the rule that an uncoupling membrane's warranty may require the unmodified grade." } ], "standards": [ { "market": "UK", "standard": "BS EN 12004 / BS 5385-1", "covers": "Adhesives for ceramic tiles including the C and S classification, and the code of practice for the design and installation of internal ceramic wall tiling." }, { "market": "US", "standard": "ANSI A118.4 / TCNA Handbook", "covers": "Modified dry-set cement mortars, and the handbook of tile installation methods with its substrate, movement joint and coverage requirements." } ], "calculators": [ { "slug": "tile-adhesive-calculator", "json": "https://craftquantities.com/api/v1/calculators/tile-adhesive-calculator.json" }, { "slug": "thinset-mortar-calculator", "json": "https://craftquantities.com/api/v1/calculators/thinset-mortar-calculator.json" }, { "slug": "crack-isolation-membrane-calculator", "json": "https://craftquantities.com/api/v1/calculators/crack-isolation-membrane-calculator.json" } ], "confusions": [ { "question": "Why does coverage behind the tile matter more than adhesive thickness?", "answer": "Because an unsupported void behind a tile is where it cracks, and notches are a means to coverage rather than an end. The trowel's job is to put ridges of adhesive down that collapse when the tile is pressed and slid into them, so the material spreads and fills the space. What the specification actually asks for is a PERCENTAGE of the tile's back in contact — commonly around eighty percent for internal dry areas and full coverage for floors, wet areas and anything external, where a void will hold water. Notch size is how you get there: a bigger tile, a less flat substrate or a deeply keyed tile back needs a bigger notch, and a large tile on a fine notch leaves hollows however much adhesive is used. The way to check is destructive and worth doing anyway — lift one tile early in the day and look at the back. Tapping for a hollow sound finds the failure later, when the floor is finished." }, { "question": "Why does adhesive go off on the wall before the tile is on it?", "answer": "Because it is a cement mortar setting chemically, and its clock starts when water is added rather than when it is exposed. Two different intervals matter and are routinely confused. POT LIFE is how long the mixed material stays usable in the bucket. OPEN TIME is how long the combed ridges on the wall stay able to wet the back of a tile pressed into them — and it is much shorter, shortened further by heat, by a dry wind, and by a porous substrate drawing water out. Once the surface has skinned, a tile pressed into it will look bedded and will have bonded to almost nothing. The fixes are all about area: comb only as much as can be tiled in a few minutes, prime a porous or dusty background so it does not drink the water, keep sun and draught off the work, and never retemper stiffening adhesive with more water, which converts a chemical failure into a weaker mix as well." }, { "question": "What does modified or flexible actually add?", "answer": "Polymer, and what it buys is adhesion to difficult surfaces plus tolerance of movement. Plain cement mortar bonds well to concrete and sand-cement render and poorly to almost everything else; adding a polymer — dry in the powder or as a liquid admixture — improves the grip on plywood, plasterboard, existing tile, and the low-porosity backs of porcelain, which absorbs almost no water and so cannot form a mechanical key by suction. The same polymer lets the set mortar deform slightly without cracking, which is what the European S1 and S2 deformability classes measure and why underfloor heating, timber floors and large-format tiles call for it. Two cautions travel with it. It is not a substitute for movement joints, which still have to pass through the tiling wherever the substrate has one. And it cures by both hydration and drying, so a modified mortar sandwiched between two impermeable layers — a porcelain tile over an uncoupling membrane — can take a very long time to develop strength, which is exactly why some membrane manufacturers specify the UNMODIFIED grade instead." } ], "related": [ "grout" ] }, { "slug": "illuminance", "concept": "Illuminance", "family": "measurement", "definition": "How much light lands on a surface, as opposed to how much a lamp emits. Measured at the working plane, and the figure a lighting specification is actually written against.", "url": "https://craftquantities.com/glossary/illuminance/", "names": [ { "market": "UK", "term": "lux", "alsoCalled": [ "lx", "illuminance", "maintained illuminance", "lumens", "working plane" ], "exactness": "false-friend", "note": "MAINTAINED illuminance is the design figure — the level at the end of the maintenance cycle, after lamp depreciation and dirt — not the level on the first day, which is higher." }, { "market": "AU", "term": "lux", "alsoCalled": [ "lx", "illuminance", "maintenance factor", "task lighting" ], "exactness": "identical", "note": null }, { "market": "US", "term": "foot-candles", "alsoCalled": [ "fc", "footcandles", "lumens per square foot", "illuminance", "light level" ], "exactness": "false-friend", "note": "A foot-candle is one lumen per square FOOT and a lux is one lumen per square METRE, so the ratio is the square-foot to square-metre factor of about 10.76, not a round ten." }, { "market": "CA", "term": "lux", "alsoCalled": [ "foot-candles", "fc", "lx", "illuminance" ], "exactness": "false-friend", "note": "Officially metric, with foot-candles still in everyday use from American products and datasheets — so a Canadian drawing can carry both units and not always say which." } ], "standards": [ { "market": "UK", "standard": "BS EN 12464-1 / SLL Code for Lighting", "covers": "Lighting of indoor work places including maintained illuminance by task, and the society's guidance on design values and maintenance factors." }, { "market": "US", "standard": "IES Lighting Handbook / ANSI/IES RP-1", "covers": "Recommended illuminance targets and design methods, and the practice for office lighting including task and ambient levels." } ], "calculators": [ { "slug": "lux-to-foot-candles-calculator", "json": "https://craftquantities.com/api/v1/calculators/lux-to-foot-candles-calculator.json" }, { "slug": "foot-candles-to-lux-calculator", "json": "https://craftquantities.com/api/v1/calculators/foot-candles-to-lux-calculator.json" } ], "confusions": [ { "question": "What is the difference between lumens and lux?", "answer": "Where you are standing. LUMENS measure the total light a source emits in every direction — a property of the lamp, printed on the box, and unchanged by what you do with it. LUX measures how much of that light lands on a square metre of surface, which depends on the lamp's output, how far away it is, how it is aimed, how much the walls and ceiling bounce back, and how many fittings there are. One lumen spread over one square metre is one lux; the same lumen spread over ten square metres is a tenth of that. So a lamp cannot have a lux rating and a room cannot have a lumen requirement, and the common domestic question — how many lumens do I need — has no answer without the room's dimensions and surfaces. It also explains why two rooms lit with identical fittings can be very different to work in: a dark ceiling and dark walls absorb the light that a pale room would return to the working plane." }, { "question": "Why is the design figure lower than the level on day one?", "answer": "Because the specification is a promise about the WORST day of the cycle rather than the best. Light output falls over time: lamps depreciate, dirt accumulates on the fitting and on the room's surfaces, and in a dusty or smoky environment it falls faster. Standards therefore specify a MAINTAINED illuminance — the level that must still be there immediately before cleaning and relamping — and the design calculation divides the target by a maintenance factor to work out how much light must be installed. The factor bundles several separate depreciations and is where optimistic design hides: assuming a clean office when the room is a workshop, or a cleaning interval nobody will keep, produces a scheme that meets its number for a year. It also means a newly commissioned installation should measure noticeably ABOVE its design figure, and one that measures exactly at target on handover will be below it within months." }, { "question": "Is 10 a safe conversion between lux and foot-candles?", "answer": "It is a safe way to sanity-check a number and an unsafe way to specify one. The exact factor is the number of square feet in a square metre, about 10.764, so using ten understates lux by roughly seven percent when converting from foot-candles and overstates foot-candles by the same when going the other way. For a rough read — is this a 300 lux office or a 30 lux corridor — that is immaterial. It stops being immaterial where a figure is a compliance threshold, where a contract specifies a level to be measured on handover, or where the error is applied in the direction that loses light: a 50 foot-candle target converted at ten gives 500 lux where the honest figure is 538, and an installation designed to the lower number can fail a measured check it would otherwise pass. The safe habit is the same one that applies to gauge and to fall on this site: carry the unit with the number, and convert with the real factor rather than the memorable one." } ], "related": [ "gauge" ] }, { "slug": "underpinning", "concept": "Underpinning", "family": "structure", "definition": "Deepening or strengthening an existing foundation while the building above it stays standing, by working in short sections so that no length is ever unsupported for long.", "url": "https://craftquantities.com/glossary/underpinning/", "names": [ { "market": "UK", "term": "underpinning", "alsoCalled": [ "mass concrete underpinning", "pin", "bay", "hit and miss", "resin injection", "mini-piling" ], "exactness": "false-friend", "note": "A PIN or BAY is one excavated section, not the whole job — quantities are counted in bays. UNDERPINNING on an insurance claim usually implies subsidence, with the disclosure that follows." }, { "market": "AU", "term": "underpinning", "alsoCalled": [ "re-blocking", "restumping", "mass concrete underpinning", "screw piles" ], "exactness": "false-friend", "note": "RESTUMPING and RE-BLOCKING are the far more common local operations — replacing the stumps under a suspended timber floor — and are not underpinning in the foundation sense at all." }, { "market": "US", "term": "underpinning", "alsoCalled": [ "pit underpinning", "helical piers", "push piers", "bench footing", "needle beam" ], "exactness": "close", "note": "BENCH FOOTING is the basement-lowering alternative that avoids underpinning entirely by stepping the new floor inward, and is usually compared against it rather than confused with it." }, { "market": "CA", "term": "underpinning", "alsoCalled": [ "bench footing", "basement lowering", "helical piles", "pit underpinning" ], "exactness": "close", "note": "Basement lowering is the dominant reason here, so the trade vocabulary is about headroom gained rather than about movement arrested." } ], "standards": [ { "market": "UK", "standard": "BS 8004 / Party Wall etc. Act 1996", "covers": "Foundations including underpinning of existing structures, and the statutory notice procedure where work goes below a neighbour's foundation level." }, { "market": "US", "standard": "IBC 1817 / ICC-ES acceptance criteria", "covers": "Underpinning requirements for adjacent and existing structures, and the evaluation criteria for helical pile foundation systems." } ], "calculators": [ { "slug": "underpinning-pit-volume-calculator", "json": "https://craftquantities.com/api/v1/calculators/underpinning-pit-volume-calculator.json" }, { "slug": "excavation-strut-load-calculator", "json": "https://craftquantities.com/api/v1/calculators/excavation-strut-load-calculator.json" } ], "confusions": [ { "question": "Why is underpinning done in short sections?", "answer": "Because the wall above has to span the gap while the section below it is open, and masonry can only arch so far. Excavating the full length under a foundation removes its support entirely and the wall comes down; excavating a metre of it leaves a short opening that the wall bridges by arching over, provided the masonry is sound and the opening is short enough. So the work proceeds in numbered bays in a HIT AND MISS sequence — dig bay one, pour it, let it gain strength, pack the gap to the underside of the old foundation, and only then open a bay that is not adjacent. The sequence and the bay width are the design, not an efficiency choice, and the two ways it goes wrong are opening too many bays at once because the ground looked stable, and packing the new concrete to the old foundation carelessly. The pack matters as much as the pour: a bay that has not been dry-packed tight to the underside carries nothing until the wall has settled onto it, which is settlement the job was meant to stop." }, { "question": "Is underpinning the right answer to subsidence?", "answer": "Often not, and the question worth asking first is what moved the ground rather than how to reach deeper. In shrinkable clay the usual cause is moisture change, and much of that is vegetation: a tree drawing water out in dry summers shrinks the clay under the footing and the building settles seasonally. Removing or managing the tree can stop the movement without touching the foundation at all — though removal has its own risk, because clay that has been kept dry for decades swells as it rehydrates and the ground HEAVES, which damages a building in the opposite direction and is harder to remedy. Other causes point elsewhere entirely: a leaking drain washing fines out of the ground is repaired by fixing the drain, and historic movement that has stopped needs monitoring rather than works. This is why competent practice is to monitor and diagnose before designing, and why underpinning part of a building is a specific decision — an underpinned section sits on different ground from the rest and can move differently, putting a crack at the junction between old and new." }, { "question": "What is the neighbour's position when the work is at a party wall?", "answer": "In England and Wales it is a statutory one, and starting without it is the most common procedural failure on this kind of job. Excavating within defined distances of a neighbouring building and to a depth below its foundations triggers a notice requirement under party wall legislation, regardless of whether the work is on the boundary, and the neighbour has rights to a schedule of condition, to appoint a surveyor at the building owner's cost, and to an award setting out how the work proceeds. The practical effects on a programme are real: notice periods run in weeks, the award has to be in place before work starts, and work begun without one can be stopped. Other markets handle the same physical risk through permits, notification and insurance rather than a dedicated statute, so an American or Australian programme brought to a British site regularly omits a step that cannot be compressed. The physical caution is the same everywhere: excavating below a neighbour's foundation undermines it, and the sequence protects their building as much as the one being worked on." } ], "related": [ "footing" ] }, { "slug": "snow-load", "concept": "Snow load", "family": "structure", "definition": "The weight of accumulated snow a roof must carry. Derived from a mapped ground value, then adjusted for the roof's shape, exposure, temperature and — decisively — for where wind piles the snow up.", "url": "https://craftquantities.com/glossary/snow-load/", "names": [ { "market": "UK", "term": "snow load", "alsoCalled": [ "sk", "characteristic ground snow load", "shape coefficient", "drifting", "exceptional snow" ], "exactness": "false-friend", "note": "sk is the GROUND value from a map and altitude correction, not the roof load. EXCEPTIONAL snow drift is a separate accidental case checked apart from the ordinary one." }, { "market": "AU", "term": "snow load", "alsoCalled": [ "alpine snow load", "sub-alpine", "ground snow load" ], "exactness": "close", "note": "Applies only in defined alpine and sub-alpine areas, so most Australian roofs are designed with no snow case at all — an absence rather than a small number." }, { "market": "US", "term": "snow load", "alsoCalled": [ "pg", "ground snow load", "pf", "flat roof snow load", "drift surcharge", "rain-on-snow", "unbalanced load" ], "exactness": "false-friend", "note": "pg is the ground value and pf the flat-roof value derived from it by exposure, thermal and importance factors. Quoting pg as the roof load overstates it; ignoring drift understates it badly." }, { "market": "CA", "term": "snow load", "alsoCalled": [ "Ss", "Sr", "ground snow load", "rain load", "accumulation factor" ], "exactness": "false-friend", "note": "Ss is snow and Sr is the associated RAIN load added on top, because rain falling onto lying snow is a Canadian design case in its own right and has no British counterpart." } ], "standards": [ { "market": "UK", "standard": "BS EN 1991-1-3 and UK National Annex", "covers": "Actions on structures from snow, including ground values, roof shape coefficients and the exceptional drift cases." }, { "market": "US", "standard": "ASCE 7 Chapter 7", "covers": "Snow loads including ground values, flat roof conversion, exposure and thermal factors, drift surcharges and unbalanced loads." } ], "calculators": [ { "slug": "roof-snow-load-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-snow-load-calculator.json" }, { "slug": "roof-snow-drift-surcharge-calculator", "json": "https://craftquantities.com/api/v1/calculators/roof-snow-drift-surcharge-calculator.json" }, { "slug": "snow-guard-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/snow-guard-spacing-calculator.json" } ], "confusions": [ { "question": "Why is drift the case that governs?", "answer": "Because wind does not leave snow where it fell. An even blanket is the easy case and rarely the worst one: wind scours snow off open areas and deposits it where the air slows down — against a parapet, in the valley of a pitched roof, on the lower roof of a stepped building, behind a rooftop plant enclosure or a solar array. The drift is a triangular pile whose peak load can be several times the uniform figure, concentrated over a narrow band, and it sits exactly where a lower roof's structure was sized for the general case. That is why a step between two roofs is a structural question rather than an architectural one, why adding a parapet or a screen to an existing roof can overload it without adding any permanent weight, and why the drift surcharge is calculated separately from the balanced load rather than being covered by a margin on it. Roof collapses under snow cluster at these features rather than in the middle of large roofs." }, { "question": "How much does snow actually weigh?", "answer": "Anything from about a twelfth of the weight of water to nearly half of it, which is why depth is a poor proxy for load. Fresh, dry, cold snow is mostly air and is light. The same snow settles under its own weight over days, and each melt-and-refreeze cycle packs it further, so an old drift can be several times as dense as it was when it fell. Rain falling onto lying snow is the extreme: the snowpack holds the water like a sponge and the load rises sharply with no change in depth at all, which is why Canadian practice carries a separate rain component and why warm-winter regions see snow failures at densities that would seem impossible from the depth. The practical reading is that a roof's remaining capacity cannot be judged by eye from the ground, and that the dangerous moment in a season is often not the heaviest snowfall but the thaw with rain that follows it." }, { "question": "Why do a warm roof and a cold roof carry different snow loads?", "answer": "Because heat leaking through a roof melts the snow on it, and the codes account for that with a thermal factor. A well-heated building with a poorly insulated roof loses enough heat to melt lying snow from below, so it sheds part of the load — and the standards allow a reduction for it. An unheated structure, a cold-roof design, or a very well insulated modern roof keeps the snow, so it carries more; the factor goes the other way and the load rises. This produces a genuinely counterintuitive result worth stating plainly: INSULATING a roof increases the snow load it must be designed for, because it stops heat doing the work. That matters most on retrofit, where a loft or flat roof is upgraded to current insulation standards on a structure sized decades ago under the old assumption — and it is the same mechanism that stops the melt that used to feed ice dams at the eaves." } ], "related": [ "ice-dam" ] }, { "slug": "concrete-grade", "concept": "Concrete strength grade", "family": "materials", "definition": "The characteristic compressive strength concrete is specified by, at a stated age and measured on a stated specimen shape. The shape is part of the number, not a detail of the test.", "url": "https://craftquantities.com/glossary/concrete-grade/", "names": [ { "market": "UK", "term": "concrete grade", "alsoCalled": [ "C25/30", "characteristic strength", "cube strength", "cylinder strength", "designated mix", "RC35" ], "exactness": "false-friend", "note": "C25/30 states BOTH: 25 MPa on a cylinder and 30 MPa on a cube, for the same concrete. A single number quoted as the grade has dropped one of the two specimens." }, { "market": "AU", "term": "concrete grade", "alsoCalled": [ "N25", "N32", "characteristic strength", "cylinder strength", "special class" ], "exactness": "false-friend", "note": "The N-number is the CYLINDER strength in MPa, so Australian N30 is close to British C30/37 rather than to C25/30 — matching the number matches the wrong specimen." }, { "market": "US", "term": "compressive strength", "alsoCalled": [ "f'c", "3000 psi", "4000 psi", "28-day strength", "design mix", "prescriptive mix" ], "exactness": "false-friend", "note": "f'c is a CYLINDER strength in psi. 4,000 psi is about 28 MPa on a cylinder, so it sits near C25/30 — which anyone converting 4,000 psi to 28 MPa and looking for C28 will miss." }, { "market": "CA", "term": "compressive strength", "alsoCalled": [ "f'c", "25 MPa", "30 MPa", "exposure class", "C-1 exposure" ], "exactness": "close", "note": "Metric MPa on cylinders like the United States, with an EXPOSURE CLASS specified alongside that can govern the mix more tightly than the strength does." } ], "standards": [ { "market": "UK", "standard": "BS 8500-1 / BS EN 206", "covers": "Concrete specification including designated and designed concretes and exposure classes, and the complementary European standard for specification, performance and conformity." }, { "market": "US", "standard": "ACI 318 / ASTM C39", "covers": "Building code requirements for structural concrete including specified compressive strength, and the test method for compressive strength of cylindrical concrete specimens." } ], "calculators": [ { "slug": "concrete-mix-ratio-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-mix-ratio-calculator.json" }, { "slug": "aci-211-water-cement-ratio-calculator", "json": "https://craftquantities.com/api/v1/calculators/aci-211-water-cement-ratio-calculator.json" }, { "slug": "rc-beam-moment-capacity-calculator", "json": "https://craftquantities.com/api/v1/calculators/rc-beam-moment-capacity-calculator.json" }, { "slug": "concrete-elastic-modulus-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-elastic-modulus-calculator.json" }, { "slug": "concrete-yield-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-yield-calculator.json" }, { "slug": "rc-column-axial-capacity-calculator", "json": "https://craftquantities.com/api/v1/calculators/rc-column-axial-capacity-calculator.json" } ], "confusions": [ { "question": "Why is a cube stronger than a cylinder of the same concrete?", "answer": "Because of friction at the testing machine's platens, and the specimen's shape decides how much that helps it. As a specimen is squashed it tries to spread sideways, and friction against the steel platens restrains it at the top and bottom — which puts that material into a confined state that is stronger than plain compression. A cube is short relative to its width, so the restrained zones from both ends reach most of the specimen and the measured strength is flattered. A standard cylinder is twice as tall as it is wide, so its middle is far enough from both platens to fail in something much closer to pure compression. The result is that the same concrete reads roughly a fifth higher as a cube, which is why British grades carry both figures and why the ratio is not a constant — it drifts with strength, so a single conversion factor applied across the range is an approximation rather than an equivalence." }, { "question": "Why 28 days, and what happens after?", "answer": "Twenty-eight days is a convention rather than a limit: it was long enough for ordinary Portland cement to reach most of its eventual strength and short enough to be a practical contractual milestone. Concrete keeps gaining strength for months and years as hydration continues — slowly, and only while moisture is available, which is why curing matters and why a slab left to dry out stops gaining. Two practical consequences follow. A 7-day result is not a failure: it is a partial result, typically a substantial fraction of the 28-day figure, and is used to predict rather than to accept. And modern mixes with fly ash or ground slag deliberately gain strength more slowly, so a mix specified for its durability can look weak at 28 days and meet its design strength at 56 or 90 — which is why the specification states the AGE as well as the strength, and why testing such a mix on the default schedule produces an argument rather than information." }, { "question": "What is characteristic strength, and why is the mix stronger than the grade?", "answer": "Characteristic strength is a statistical floor, not an average: it is the value below which only a small proportion of test results — conventionally five percent — are expected to fall. Because real concrete varies from batch to batch, a supplier aiming AT the characteristic value would fail half the time, so they target a mean strength above it by a margin that depends on how consistent their production is. A plant with tight control needs a smaller margin; one with variable materials needs a larger one. Three things follow from this. Concrete routinely tests well above its grade, and that is the design working rather than generosity. A single low cube is not automatically a failure — conformity is judged on a rule about groups of results. And specifying a higher grade to be safe raises the cement content, which raises cost, shrinkage and heat of hydration, so it is a trade rather than a free margin." } ], "related": [ "slump", "concrete-curing" ] }, { "slug": "steel-grade", "concept": "Structural steel grade", "family": "materials", "definition": "The designation naming a structural steel's strength and toughness. In one system the number states the yield strength; in the other it identifies the specification document.", "url": "https://craftquantities.com/glossary/steel-grade/", "names": [ { "market": "UK", "term": "steel grade", "alsoCalled": [ "S275", "S355", "JR", "J0", "J2", "yield strength", "subgrade" ], "exactness": "false-friend", "note": "The number is the YIELD STRENGTH in MPa. The letters after it — JR, J0, J2, K2 — are the toughness subgrade, a separate property that governs brittle fracture and is not optional." }, { "market": "AU", "term": "steel grade", "alsoCalled": [ "300PLUS", "AS/NZS 3679", "Grade 300", "Grade 350" ], "exactness": "close", "note": "Numbers are yield strength in MPa as in Europe, but the Australian sections and their standard grades are their own — Grade 300 is not S275 and the sections differ too." }, { "market": "US", "term": "steel grade", "alsoCalled": [ "A992", "A36", "A572 Gr 50", "ksi", "Fy", "dual certified" ], "exactness": "false-friend", "note": "A992 and A36 are ASTM SPECIFICATION numbers, not strengths. A992 is the standard wide-flange grade at 50 ksi yield, and its number encodes nothing about that." }, { "market": "CA", "term": "steel grade", "alsoCalled": [ "CSA G40.21", "350W", "300W", "W", "WT", "A" ], "exactness": "false-friend", "note": "350W reads as 350 MPa yield with a WELDABLE suffix, so the Canadian system states the property like Europe and appends a category letter the European one does not." } ], "standards": [ { "market": "UK", "standard": "BS EN 10025-2 / BS EN 1993-1-10", "covers": "Hot rolled products of structural steels including the S grades and JR to K2 subgrades, and material toughness selection against brittle fracture." }, { "market": "US", "standard": "ASTM A992 / ASTM A36 / AISC 360", "covers": "Structural steel shapes for building framing and the general carbon structural steel specification, and the specification for structural steel buildings." } ], "calculators": [ { "slug": "steel-girder-ltb-limit-calculator", "json": "https://craftquantities.com/api/v1/calculators/steel-girder-ltb-limit-calculator.json" }, { "slug": "steel-moment-connection-bolt-calculator", "json": "https://craftquantities.com/api/v1/calculators/steel-moment-connection-bolt-calculator.json" }, { "slug": "steel-baseplate-bearing-calculator", "json": "https://craftquantities.com/api/v1/calculators/steel-baseplate-bearing-calculator.json" }, { "slug": "hss-composite-column-calculator", "json": "https://craftquantities.com/api/v1/calculators/hss-composite-column-calculator.json" }, { "slug": "castellated-beam-net-shear-calculator", "json": "https://craftquantities.com/api/v1/calculators/castellated-beam-net-shear-calculator.json" }, { "slug": "structural-steel-weld-shear-calculator", "json": "https://craftquantities.com/api/v1/calculators/structural-steel-weld-shear-calculator.json" } ], "confusions": [ { "question": "Is S355 the same as A572 Grade 50?", "answer": "Close in yield strength and not interchangeable, and the difference is in everything the yield number does not cover. S355 has a nominal yield of 355 MPa; Grade 50 has 50 ksi, about 345 MPa — near enough that the substitution looks free. What differs is the rest of the specification: the chemistry and therefore the weldability, the carbon equivalent that governs preheat, the tensile-to-yield ratio, the elongation, and above all the TOUGHNESS regime, which the European system states explicitly in the subgrade letter and the American system handles differently. There is also a dimensional trap underneath it: European and American sections are not the same shapes, so a beam substituted by grade still has different flange and web dimensions, different section properties and different connection geometry. Grade equivalence tables exist and are useful for estimating; they are not an approval, and the approval is the engineer's." }, { "question": "What does the JR, J0 or J2 suffix actually control?", "answer": "The temperature at which the steel stops behaving ductilely and starts breaking like glass. Structural steel absorbs a lot of energy before failing at room temperature and much less when cold, and the transition is fairly sharp; the subgrade states the temperature at which a specified impact energy is still achieved — JR at room temperature, J0 at zero, J2 at minus twenty, K2 with a higher energy requirement. The selection depends on the service temperature, the thickness of the material, and whether the detail is in tension with stress concentrations, which is why the design standard has whole tables for it rather than a rule of thumb. It matters because brittle fracture gives no warning, propagates fast and happens at stresses well below yield. Specifying S355 without a subgrade is an incomplete specification, and substituting JR where J2 was called for is the kind of change that looks like a like-for-like swap on a delivery note." }, { "question": "Why does dual certification exist, and is it a problem?", "answer": "Because modern steelmaking made it hard to produce steel weak enough to be A36 only. A992 was introduced with a yield RANGE and a capped maximum, because a mill running to a minimum will often exceed it comfortably, and material rolled to A992 also satisfies A36's requirements — so a section gets certified to both and the mill can sell it into either order. For ordinary strength design that is a benefit: the steel meets whatever the drawing asked for. It becomes a problem in the cases that depend on the steel NOT being stronger than assumed. Seismic capacity design deliberately makes one element yield before another fails, and a beam that is substantially stronger than specified can push the failure into the element that was supposed to stay elastic. That is precisely why A992 caps its yield and specifies a maximum yield-to-tensile ratio, and why a designer relying on a plastic hinge forming in a particular place has to specify the grade rather than accept whatever the yard certified twice." } ], "related": [ "rsj" ] }, { "slug": "ductwork", "concept": "Ductwork", "family": "services", "definition": "The sheet-metal or fabric distribution system carrying air around a building. Specified by its construction class, its pressure class and how much air it is permitted to leak.", "url": "https://craftquantities.com/glossary/ductwork/", "names": [ { "market": "UK", "term": "ductwork", "alsoCalled": [ "DW/144", "DW/143", "low pressure", "medium pressure", "air leakage class", "spiral duct" ], "exactness": "false-friend", "note": "DW/144 is a single specification covering construction and gauge by pressure class; DW/143 is the leakage testing method. Neither name exists in American practice, and neither is SMACNA." }, { "market": "AU", "term": "ductwork", "alsoCalled": [ "AS 4254", "flexible duct", "rigid duct", "duct class" ], "exactness": "close", "note": "Follows its own standard with flexible duct used far more widely in housing than in Britain, which changes the effective resistance of a system far more than the fittings do." }, { "market": "US", "term": "ductwork", "alsoCalled": [ "duct", "SMACNA", "pressure class", "leakage class", "CL", "gauge", "sheet metal" ], "exactness": "false-friend", "note": "SMACNA gives construction by pressure class in inches of water gauge; the LEAKAGE class is specified separately and is not implied by the construction class the way DW/144 implies it." }, { "market": "CA", "term": "ductwork", "alsoCalled": [ "duct", "SMACNA", "pressure class", "leakage class", "sheet metal" ], "exactness": "close", "note": "As the United States, with pressure still commonly quoted in inches of water gauge even where the rest of the design is metric." } ], "standards": [ { "market": "UK", "standard": "DW/144 / DW/143", "covers": "Specification for sheet metal ductwork including gauge, stiffening and pressure class, and the practical guide to ductwork leakage testing." }, { "market": "US", "standard": "SMACNA HVAC Duct Construction Standards / ASHRAE 90.1", "covers": "Metal and flexible duct construction by pressure class, and the energy standard's duct sealing and leakage testing requirements." } ], "calculators": [ { "slug": "duct-size-calculator", "json": "https://craftquantities.com/api/v1/calculators/duct-size-calculator.json" }, { "slug": "duct-air-velocity-calculator", "json": "https://craftquantities.com/api/v1/calculators/duct-air-velocity-calculator.json" }, { "slug": "duct-leakage-class-calculator", "json": "https://craftquantities.com/api/v1/calculators/duct-leakage-class-calculator.json" }, { "slug": "duct-fitting-equivalent-length-calculator", "json": "https://craftquantities.com/api/v1/calculators/duct-fitting-equivalent-length-calculator.json" }, { "slug": "duct-hanger-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/duct-hanger-spacing-calculator.json" }, { "slug": "duct-silencer-insertion-loss-calculator", "json": "https://craftquantities.com/api/v1/calculators/duct-silencer-insertion-loss-calculator.json" }, { "slug": "flex-duct-friction-loss-calculator", "json": "https://craftquantities.com/api/v1/calculators/flex-duct-friction-loss-calculator.json" }, { "slug": "equivalent-round-duct-diameter-calculator", "json": "https://craftquantities.com/api/v1/calculators/equivalent-round-duct-diameter-calculator.json" } ], "confusions": [ { "question": "What is a pressure class, and why does it decide the gauge?", "answer": "It is the pressure the duct must hold without deforming, and it sets the metal thickness and the stiffening because a duct is a pressure vessel with flat sides. Round duct resists pressure by its shape and needs little help. A rectangular duct's flat panels want to bow outward under positive pressure and suck inward under negative, so the thicker the metal and the closer the stiffening beads or angles, the higher the pressure it can take without drumming, leaking at the seams or visibly deflecting. Both markets therefore specify construction AGAINST a pressure class rather than as a single thickness — and the classes themselves are stated in different units, inches of water gauge in North America and pascals in Britain. The practical trap is that the class is a property of the SYSTEM at that point, not of the fan: duct upstream of a damper can sit at a much higher pressure than the design figure quoted for the branch, and the highest pressure any section sees is what governs its construction." }, { "question": "Is a leakage class the same thing as a pressure class?", "answer": "No, and conflating them is the commonest specification error in ductwork. PRESSURE class says what the duct must withstand. LEAKAGE class says how much air it is permitted to lose at that pressure, expressed as a flow per unit of duct surface area. They are related — leakage rises with pressure — but a duct can be built stiff enough for its pressure and still leak badly, because leakage is a property of the SEAMS and joints rather than of the panels. British practice ties the two together in one document, so quoting a DW/144 class implies a leakage class. American practice specifies them separately, so a drawing that names a SMACNA pressure class and stops has said nothing about leakage at all. That gap matters commercially as well as technically: sealing to a tighter leakage class is labour on every joint, and discovering it after fabrication is a variation rather than a detail." }, { "question": "Why does a flexible duct ruin a design that calculated correctly?", "answer": "Because its resistance depends on how it was installed, and the figure in the calculation assumed it was straight. Flexible duct has a corrugated bore, so even fully extended it has several times the resistance of smooth rigid duct of the same diameter. Left compressed — shipped in a carton at a fraction of its length and simply pushed into place — that resistance multiplies again, and a lazy bend sagging between hangers adds more. A branch specified for a given flow can end up delivering a fraction of it while the system's fan runs at its design speed, which shows up as a room that never reaches temperature and a balancing exercise that cannot close. This is why every flexible connection has a maximum permitted length in the specification, why it should be pulled taut and supported at intervals rather than draped, and why replacing a run of rigid duct with flexible during installation is a design change rather than a substitution." } ], "related": [ "mvhr" ] }, { "slug": "concrete-curing", "concept": "Curing", "family": "materials", "definition": "Keeping fresh concrete moist and within a temperature range long enough for hydration to continue. Not drying, and not the same thing as setting, which happens far earlier.", "url": "https://craftquantities.com/glossary/concrete-curing/", "names": [ { "market": "UK", "term": "curing", "alsoCalled": [ "curing period", "curing compound", "maturity", "cold weather working", "plastic shrinkage" ], "exactness": "false-friend", "note": "CURING is often used loosely for setting or hardening. The regulated quantity is a curing PERIOD that lengthens with cold and with slower cements, not a fixed number of days." }, { "market": "AU", "term": "curing", "alsoCalled": [ "curing compound", "moist curing", "evaporation rate", "plastic shrinkage cracking" ], "exactness": "close", "note": "Evaporation rate is the daily governing concern here rather than freezing, so the practical emphasis falls on wind breaks, fogging and early covering." }, { "market": "US", "term": "curing", "alsoCalled": [ "moist curing", "curing compound", "maturity method", "hot weather concreting", "cold weather concreting", "protection" ], "exactness": "close", "note": "PROTECTION is named separately from curing — curing supplies moisture, protection holds temperature — and hot and cold weather concreting each have their own guide." }, { "market": "CA", "term": "curing", "alsoCalled": [ "moist curing", "protection", "maturity", "cold weather protection", "hoarding" ], "exactness": "false-friend", "note": "HOARDING here means the heated enclosure built over a winter pour, not the site fence the same word means in Britain — two unrelated things on the same site." } ], "standards": [ { "market": "UK", "standard": "BS EN 13670 / BS 8500-1", "covers": "Execution of concrete structures including curing classes and the periods they require, and the specification's exposure and cement-type provisions that lengthen them." }, { "market": "US", "standard": "ACI 308.1 / ACI 305R / ACI 306R", "covers": "Specification for curing concrete, and the guides to hot weather and cold weather concreting including protection periods and maturity methods." } ], "calculators": [ { "slug": "concrete-maturity-method-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-maturity-method-calculator.json" }, { "slug": "concrete-mix-temperature-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-mix-temperature-calculator.json" }, { "slug": "concrete-evaporation-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-evaporation-calculator.json" }, { "slug": "mass-concrete-thermal-gradient-calculator", "json": "https://craftquantities.com/api/v1/calculators/mass-concrete-thermal-gradient-calculator.json" } ], "confusions": [ { "question": "Is curing the same as drying?", "answer": "It is the opposite, and treating them as the same is how a slab is permanently weakened on its first day. Concrete gains strength by HYDRATION — cement reacting with water — and that reaction continues only while water is present. A slab that is allowed to dry stops hydrating, and the strength it has not gained by then it never gains: the reaction does not resume when it rains next week, because the microstructure has already formed around the water that was there. So curing means keeping water IN, by ponding, by covering with polythene or wet hessian, by fogging, or by spraying a curing compound that forms a film to stop evaporation. The confusion is reinforced by everyday language — nobody says a floor is curing, they say it is drying before the tiles go down — and that later drying, of a hardened slab losing its residual moisture before a floor finish, is a genuinely different process happening weeks afterwards." }, { "question": "Why does concrete crack before it has set?", "answer": "Because water leaves the surface faster than bleed water rises to replace it, and PLASTIC SHRINKAGE cracks open in concrete that is still soft. The rate depends on four things together — air temperature, concrete temperature, relative humidity and wind speed — and wind is the one people underestimate: a moderate breeze can multiply the evaporation rate several times over on an otherwise unremarkable day. Above roughly a litre per square metre per hour the risk is high, which is the figure the standard evaporation nomograph exists to estimate. The cracks are typically shallow, roughly parallel and open within the first few hours, and they are entirely preventable by the measures that reduce evaporation: wind breaks, fogging the air above the surface, covering between operations, and not pouring a large flat area into a drying wind at all. They are also not structural cracks, which is why they are so often dismissed — and why they later become a durability problem in a slab exposed to salt." }, { "question": "What does the maturity method actually let you do?", "answer": "Stop guessing when concrete is strong enough, and stop breaking cubes to find out. Strength gain depends on temperature as well as time, so a cylinder cured in a laboratory tells you little about a slab that spent its first night at four degrees. The maturity method instead logs the concrete's own temperature history, converts it into a maturity index, and reads strength off a curve established for that specific mix by breaking specimens at known maturities. Because the sensor is in the element itself, it reports what that element has actually achieved — so formwork can be struck, a slab loaded, or post-tensioning stressed as soon as the element is ready rather than on a calendar. The two conditions people forget are that the calibration curve belongs to ONE mix — change the cement source and it is void — and that it measures strength, not durability, so it cannot shorten a curing period specified for cover protection rather than for load." } ], "related": [ "concrete-grade" ] }, { "slug": "concrete-placing", "concept": "Placing and compaction", "family": "materials", "definition": "Getting concrete into the form without separating it, and then removing the entrapped air. Compaction is what turns a placed mix into the material the design assumed.", "url": "https://craftquantities.com/glossary/concrete-placing/", "names": [ { "market": "UK", "term": "placing", "alsoCalled": [ "pour", "compaction", "poker vibrator", "segregation", "honeycombing", "self-compacting concrete" ], "exactness": "false-friend", "note": "POUR is universal on site and misleading — concrete is placed as close as possible to its final position. HONEYCOMBING names the voided surface that poor compaction leaves." }, { "market": "AU", "term": "placing", "alsoCalled": [ "pour", "compaction", "immersion vibrator", "bug holes", "segregation" ], "exactness": "close", "note": "As British practice, with pumping the default delivery method on most sites, so pumpability governs the mix design more often than placeability by skip does." }, { "market": "US", "term": "placement", "alsoCalled": [ "pour", "consolidation", "internal vibrator", "segregation", "bugholes", "SCC" ], "exactness": "false-friend", "note": "CONSOLIDATION is the American word for compaction and has its own guide. BUGHOLES names the small surface voids British practice calls blowholes, distinct from honeycombing." }, { "market": "CA", "term": "placement", "alsoCalled": [ "consolidation", "internal vibrator", "cold joint", "SCC", "pumping" ], "exactness": "close", "note": "As the United States, with cold-weather placing constraints so routine that the placing method is usually chosen around the protection regime rather than the other way round." } ], "standards": [ { "market": "UK", "standard": "BS EN 13670 / BS EN 206", "covers": "Execution of concrete structures including placing, compaction and permitted free-fall, and the consistence classes that describe how a mix will flow." }, { "market": "US", "standard": "ACI 309R / ACI 304R", "covers": "Guide for consolidation of concrete including vibrator radius of action and insertion spacing, and the guide for measuring, mixing, transporting and placing concrete." } ], "calculators": [ { "slug": "concrete-vibrator-insertion-spacing-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-vibrator-insertion-spacing-calculator.json" }, { "slug": "concrete-pump-friction-loss-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-pump-friction-loss-calculator.json" }, { "slug": "concrete-slump-flow-calculator", "json": "https://craftquantities.com/api/v1/calculators/concrete-slump-flow-calculator.json" }, { "slug": "scc-formwork-pressure-calculator", "json": "https://craftquantities.com/api/v1/calculators/scc-formwork-pressure-calculator.json" }, { "slug": "frc-fiber-dosage-calculator", "json": "https://craftquantities.com/api/v1/calculators/frc-fiber-dosage-calculator.json" } ], "confusions": [ { "question": "What does a vibrator actually do, and how far does it reach?", "answer": "It liquefies the concrete around it briefly so entrapped air can rise out and the mix can close around the reinforcement — and it does that over a RADIUS OF ACTION that is a property of the poker, not of the operator's patience. The radius depends on the vibrator's head diameter and frequency and on the mix, and insertions have to overlap it, which is why guides give a spacing rather than an instruction to move it about. Three errors follow from not knowing the radius. Spacing the insertions too far apart leaves unconsolidated wedges between them, which surface as honeycombing at the form face. Leaving the poker in too long lets the heavy aggregate settle and the paste rise, segregating the very concrete being compacted. And using the poker to push concrete sideways along the form — the most common misuse — moves the paste further than the stones, so the material that arrives at the far end is not the mix that left the truck." }, { "question": "Why is adding water on site so damaging?", "answer": "Because strength is governed by the ratio of water to cement, and water added at the truck raises that ratio for the whole load without adding any cement to match. The rule of thumb that circulates on site — a bucket or two will not matter — is wrong by a margin that is easy to miss: a modest addition to a full load can cost a substantial fraction of the design strength, and it also increases shrinkage, increases permeability, and lowers durability in ways no cube test taken before the addition will show. The legitimate answer to concrete that is too stiff to place is a PLASTICISER, which increases workability without increasing water, added under control and recorded. That is also why a delivery ticket records the water added and why a mix that has been re-tempered on site is, strictly, a different concrete from the one specified — and why the supplier's liability usually ends at the moment somebody puts a hose in the drum." }, { "question": "If self-compacting concrete needs no vibration, why not use it everywhere?", "answer": "Because it moves the difficulty rather than removing it. SCC is designed to flow into place and de-air under its own weight, which is transformative in congested reinforcement, in thin sections and where vibration is impractical or would disturb something — and it is measured by SLUMP FLOW, the spread diameter of a slumped cone, rather than by how far the cone subsided. The costs are real. It is more expensive, because the flow comes from admixtures and a higher fines content rather than from water. It is far more sensitive to variation: a small change in aggregate moisture can take it from flowing correctly to segregating, so it needs tighter batching control than a conventional mix. And it exerts close to full hydrostatic pressure on formwork, because it does not arch or stiffen as it fills — so forms designed for a conventional pour rate can be badly under-designed for it, which is why SCC formwork pressure is calculated separately rather than assumed." } ], "related": [ "slump" ] } ] }