Craft QuantitiesSide by side
Half the questions in construction are not “how much do I need” but “which one” — tile or vinyl, metal or shingles, tank or tankless.
Each page takes one decision apart into the factors that actually differ: how each option fails, what it demands of the substrate, the climate and the owner, and which situations settle the question before taste gets a vote. Then it hands you both calculators, because the honest end of a comparison is running your own numbers on each side.
Matches either option by name, the calculators behind them, and the factors each comparison weighs — so “substrate” finds every decision that turns on one.
200 comparisons
Decisions you cannot revisit. Everything here is buried, cast or bearing within days of the choice, and the cost of changing your mind is measured in demolition rather than restocking.
Bags win on access, on discrete pours and on the freedom to stop; the truck wins the moment the concrete has to arrive as one continuous mass. Volume is only the crude proxy — the real test is whether a cold joint would matter.
EitherBagged concrete, mixed on site
OrReady-mix delivered by truck
9 factors weighed
Block is labour spread thin across days and pausable at every course; poured is a week of formwork and one hour that cannot be repeated. Site access and which trade your market actually has usually settle this before engineering gets a vote.
EitherCMU block foundation wall
OrPoured concrete foundation wall
8 factors weighed
A helical pile leaves the ground with a measured capacity and carries load the same hour; a poured pier leaves a hole, a cure, and a bearing value taken on trust. How bad the ground is, and whether you are supplying the labour, decide this more often than the foundations themselves do.
EitherHelical screw piles
OrPoured concrete piers
9 factors weighed
Pads carry points; a strip carries a line. If nothing between the posts needs holding up, pads are less digging and less concrete — but the moment a masonry skin, a bearing wall, a slab edge or a sealed perimeter arrives between them, the strip stops being the expensive option and becomes the only one doing the whole job.
EitherIsolated pad footings
OrContinuous strip footing
9 factors weighed
Fibres act in the first hours, while the concrete is still plastic; steel acts for the rest of the slab's life, deciding what each crack does once it has formed. Only an engineered macro-fibre design substitutes for rebar, and a bag in the truck is not one.
EitherSteel rebar / mesh grid
OrFibre-reinforced concrete
8 factors weighed
A skid frame is a base you can lay in an afternoon, re-level in another, and drag off the plot entirely; a slab is the floor itself and is never leaving. What is going inside decides this more often than the ground does — and in some places, so does what a permanent base does to the shed's standing with the planning office.
EitherTimber skid frame on gravel
OrPoured concrete slab
9 factors weighed
Post-tensioning buys stiffness, a jointless floor and cracks that stay shut, out of less concrete and far less steel by weight. It pays for that with a slab nobody may cut, core or pier without a specialist and a tendon map. Your soil report decides whether either is enough; your local market and your future plans decide which one you should actually build.
EitherPost-tensioned slab
OrConventionally reinforced slab
9 factors weighed
A segmental wall works by building a reinforced block of soil behind the face; a poured cantilever works by standing on a footing wide enough that the earth's own weight holds it down. Whether you own — and can dig into — the ground behind the wall usually settles this before height does.
EitherSegmental block (SRW) wall
OrPoured reinforced concrete wall
8 factors weighed
Mass underpinning needs no plant and works in a cellar, and it runs out of practicality with depth. Mini piles reach a competent stratum at any depth and need a rig, headroom and a way in. Depth and access decide it — and neither should be chosen before the cause of the movement is understood.
EitherMass concrete underpinning
OrMini piles with a needle or cap
8 factors weighed
Dewatering is cheap to mobilise, works only in permeable ground, must run without interruption, and settles everything inside its cone of depression. A cut-off costs more, is indifferent to a power cut, and only works if it reaches an impermeable layer. Permeability and the neighbours decide it.
EitherDewatering — wellpoints or deep wells
OrCut-off — secant or contiguous piles
8 factors weighed
Digging deep is simple, universally accepted and costs whatever the frost depth is. Insulating is far less excavation and concrete, and it is a designed system that depends on insulation nobody will ever see again. For a heated building in a severe climate it is a large saving; for an unheated one it is a different design.
EitherFrost-protected shallow foundation
OrFooting below the frost line
8 factors weighed
A barrier resists water and has to be perfect to do it. A drained cavity accepts water and removes it, so a defect is not a failure — at the price of a pump, a channel that needs flushing, and a system that stops in a power cut. Grade of use and the structure's condition decide it.
EitherTanking — a barrier system
OrDrained cavity membrane
8 factors weighed
Piles bypass poor ground and carry load to a competent stratum. Ground improvement makes the poor ground itself adequate, so ordinary shallow foundations work. The first question is whether there is a competent layer within reach — and a pile group never carries the sum of its individual capacities.
EitherPiling
OrGround improvement
10 factors weighed
Soil nailing is built top-down into ground that is already there, so it can stabilise a cut beneath something that cannot be moved. A reinforced soil wall is built bottom-up in compacted layers, which means excavating the whole reinforced zone first — and that zone reaches far further back than the face suggests.
EitherSoil nailing
OrReinforced soil wall
10 factors weighed
A sheet has a factory-guaranteed thickness everywhere except its seams; a liquid has no seams but a thickness that is entirely the applicator's. Opposite failure geometries — one fails at laps, the other where it went on thin. Both are buried immediately afterwards and unrepairable from inside.
EitherSheet membrane
OrLiquid-applied membrane
10 factors weighed
Sizing the footing asks whether the ground can carry the pressure beneath it. Stability asks whether the wall overturns, slides, or rotates out on a failure surface passing under the whole thing. They fail differently and passing one proves nothing about the other — and drainage changes the load on all of them.
EitherFooting sizing (bearing)
OrStability checks
10 factors weighed
A protection board shields the membrane from backfill damage, and that is all it does. A sheet drain does that and creates a continuous path to the footing drain, removing the hydrostatic head the waterproofing would otherwise resist. Either way, the drainage only works if the bottom discharges somewhere.
EitherDrainage composite (sheet drain)
OrProtection board
10 factors weighed
A spread footing distributes load over a wide area at shallow depth, so it depends entirely on the soil immediately beneath. A pier carries load down to a better stratum, and resists uplift through shaft friction — which is why it suits wind-loaded columns and expansive clay, where the ground pushes up.
EitherSpread footing
OrDrilled pier
10 factors weighed
A raw blow count depends on the confining stress at the depth it was taken, so the same soil gives a higher N deeper down. Correcting for overburden — and for the energy the particular hammer delivered — is what makes the number comparable. Relative density is the property the correction is aiming at.
EitherCorrected SPT N-value
OrRelative density
10 factors weighed
How the load gets to the ground, and what the frame costs you in depth, span and trade sequence. Most of these trade an expensive material against expensive labour, and the site conditions usually settle it.
Neither wins outright, and most real frames use both: welded in the shop where position, weather and inspection are controlled, bolted in the field where tolerance and crane time decide. What settles an individual joint is where it will be made, whether there is a back face to get a wrench onto, whether the design wants the joint rigid or rotating, and whether anything here is ever meant to come apart.
EitherBolted connection
OrWelded connection
9 factors weighed
Cast-in wins on the load path and on depth, which is nearly free before the pour and expensive afterwards. Post-installed wins on layout, which is the thing that actually goes wrong. Whether you control the pour usually settles this long before capacity does.
EitherCast-in anchor bolts
OrPost-installed (drilled) anchors
9 factors weighed
One member is manufactured to a dimension and holds it; the other dries to one and moves getting there. I-joists cross distances solid lumber cannot reach without a beam under the middle, arrive straight and let services through their webs, and pay for it in price, lead time, unforgiving bearing details and a thin web that fails early in a fire. Which one wins is usually settled by the span you have to cross and by whether anything is ever going to protect the underside.
EitherEngineered wood I-joists
OrSolid-sawn dimensional lumber joists
9 factors weighed
ICF delivers continuous insulation, airtightness and mass as properties of the system rather than results of workmanship — and charges for it up front, in a wall whose openings are settled before the pour. Framing is cheaper to build, far cheaper to change, and reaches similar numbers if your trades will detail it properly.
EitherInsulated concrete forms (ICF)
OrWood stud framing
9 factors weighed
One floor is manufactured in a factory and finished the hour it lands; the other is made in place and is not a floor until the concrete says so. Timber buys a dry, light, fast deck and pays for it in vibration, impact sound and a design freeze months earlier than anyone is used to. How severe your acoustic criteria are, and whether the grid can be drawn to panel widths and then repeated, decide this far more often than the materials do.
EitherCLT / mass timber floor panels
OrReinforced concrete slab
9 factors weighed
Over purlins the panel is the structure and carries itself between rows; over a deck it is only a skin. The deck buys a supported second water barrier, an airtight plane, a walkable roof and a substrate for whatever comes next — but its cost is close to pure area, and the frame you already have usually settles the argument before any of that is weighed.
EitherPurlins over rafters or trusses
OrSolid plywood / OSB deck
9 factors weighed
A ridge board is a spacer — the ceiling joists are what hold the roof together, working in tension, and the ceiling they make is flat. A structural ridge beam does that job overhead instead, and asks for a post at each end with a clear path down to a footing. The vault is what you buy; the posts are the price.
EitherStructural ridge beam
OrRidge board with rafter ties
9 factors weighed
Steel is the shallowest beam that will do the job, and it asks to be paid in weight, plant and a fabricator's drawing. Engineered timber is far lighter for the same opening, takes a screw anywhere along it, and in its multi-ply form can be carried in one ply at a time — and it asks to be paid in depth. Measure the depth you can spare and the route into the room — between them they usually settle this before anyone's preference gets a vote.
EitherStructural steel beam
OrGlulam / engineered timber beam
8 factors weighed
Steel is straighter and will not burn, rot or feed anything: the better frame for a wall that only has to stand there. Wood is the one you can screw into in ten years without having planned for it.
EitherCold-formed steel studs
OrDimensional lumber studs
9 factors weighed
Trusses buy speed, clear span and a design frozen before work starts, and spend the roof void to do it. Cut rafters keep the volume and stay changeable, paid for in carpentry hours.
EitherEngineered roof trusses
OrStick-framed common rafters
9 factors weighed
A timber post buys its capacity with bulk and a steel column buys it with a thin, very stiff shell, so the steel one stands in a fraction of the floor space and shrugs off a wet base. What that slimness costs is a fabricated part frozen at a length, nothing to nail to, and fire protection the timber post can carry in its own thickness. Before any of that decides it, find out whether the post is braced by a wall or standing free — the same member is two different problems.
EitherSolid timber post
OrSteel / concrete-filled steel column
9 factors weighed
A castellated beam turns the same steel into a deeper member, which is worth a great deal where deflection governs and services need to pass through. It gives up web, so shear and two buckling modes it invents become the checks. On short heavily loaded spans it is the wrong tool — the openings are where the shear is.
EitherCastellated or cellular beam
OrPlain rolled girder
8 factors weighed
A filled tube is dramatically smaller for the same load, because the steel confines the concrete and the concrete braces the steel — each improves the other. It also decouples the concrete from the erection sequence. An RC column is cheaper in material, inherently better in fire, and stiffer where the frame relies on monolithic joints.
EitherReinforced concrete column
OrConcrete-filled steel tube
8 factors weighed
A pier is bulky, excellent in compression and worthless in tension, and its capacity falls steeply as it gets tall for its thickness. A post is slender, carries tension and compression, and lives or dies on the detail at its base. Both are governed by end conditions, which are worth more than the material.
EitherMasonry pier
OrTimber post
8 factors weighed
I-joists span a long way at close centres for very little material, and they punish any cut in the wrong place. Glulam is solid, carries point loads anywhere, chars predictably in fire and can be left exposed. Whether the floor is a field of repeating joists or a few beams carrying loads usually settles it.
EitherGlulam beam
OrEngineered I-joist
8 factors weighed
Scissor trusses arrive complete and need no ridge support, and they spread at their bearings in a way the walls have to be detailed for. A ridge beam gives a true vault to the apex and needs posts and a load path carrying half the roof. The vault angle you want usually decides which is even available.
EitherScissor trusses
OrRafters on a structural ridge beam
8 factors weighed
A spiral saves floor area and pays for it in headroom, usable tread width and the fact that nothing large will ever go up it. A straight flight costs length and gives a stair anyone can use carrying anything. In most buildings the deciding question is whether the spiral is permitted to be the only stair at all.
EitherSpiral stair
OrStraight or dog-leg flight
8 factors weighed
ICF puts a continuous concrete core inside continuous insulation, which removes thermal bridging through the structure entirely — and it is formwork, so the pour is a temporary works operation that can fail expensively. Blockwork is incremental, familiar and forgiving, and it bridges heat at every joint and web.
EitherInsulated concrete formwork
OrConcrete blockwork
10 factors weighed
A loft conversion uses space you already own and keeps the garden. Head height decides whether it is possible at all — and it is eaten from both ends, by a new floor above the joists and a new ceiling below the rafters. An extension has no such gate, and takes garden, foundations and drainage instead.
EitherLoft conversion
OrExtension
10 factors weighed
Nearly all of concrete's embodied carbon is in the cement, so replacing a share of it cuts the figure close to proportionally while changing nothing about the design. Switching material saves more and changes everything — and the by-product supply that makes the first option work is finite and shrinking.
EitherLower-carbon concrete (SCM replacement)
OrChanging the structural material
10 factors weighed
Deflection is static — how far the member sags — and it protects finishes and appearance. Vibration is dynamic, governed by frequency, mass and damping, and it protects how the floor feels. A long-span lightweight floor can pass the first comfortably and fail the second.
EitherDeflection limit
OrVibration check
10 factors weighed
Market value includes the land, and land does not burn down. Rebuild cost is what it takes to construct the building again at today's prices to today's regulations, plus demolition and fees. They diverge in both directions, and insuring for the wrong one either wastes premium or triggers proportional settlement.
EitherRebuild (reinstatement) cost
OrMarket value
10 factors weighed
Concrete hydrates rather than dries, and water lost to evaporation is strength that never arrives. A compound seals the surface in one pass and cannot be checked afterwards; a covering is visible, adds insulation in cold weather, and takes labour. The surface is what suffers either way.
EitherCuring compound
OrCoverings and blankets
10 factors weighed
Conventional concrete exerts less than full hydrostatic pressure, because it develops internal friction as it stiffens — and the standard formulas depend on that. Self-compacting concrete is designed to have no such resistance, so it pushes at nearly full hydrostatic and formwork sized the conventional way is under-designed.
EitherSelf-compacting concrete
OrConventional concrete
10 factors weighed
Camber is a built-in upward curvature that flattens under dead load. It is a fabrication instruction, not stiffness — it does not reduce deflection and does nothing about live load, which is what most limits govern. A cambered member arrives bowed, and forcing it flat defeats the purpose.
EitherCamber
OrDeflection
10 factors weighed
Development length is how far one bar must be embedded to develop its strength through bond with the concrete. A lap splice passes force from one bar to another through the concrete between them — two transfers, not one — so it is longer. Both fall with top-bar position, because bleed water collects under the bar.
EitherLap splice length
OrDevelopment length
10 factors weighed
Capacity asks whether the lintel can span the opening. Bearing asks whether the masonry under its ends can take the reaction — because a lintel concentrates the whole load above into two small areas. And masonry arches over an opening, so the load is usually less than the full wall above it.
EitherLoad capacity
OrBearing length
10 factors weighed
Concrete masonry shrinks and clay brickwork expands, so the two need opposite provisions. Control joints decide where a shrinkage crack goes; bed joint reinforcement distributes it into many invisible ones, which is what permits wider joint spacing. They are complementary, not alternatives.
EitherControl joints
OrBed joint reinforcement
10 factors weighed
Operational carbon falls as buildings get more efficient and grids decarbonise; embodied carbon does not. So embodied becomes a larger share over time and can be the majority on an efficient new building — and it is spent up front, which matters against a budget that runs out on a date.
EitherOperational carbon
OrEmbodied carbon
10 factors weighed
A connection is as strong as its weakest failure mode, and the plate has three the bolts do not: net section rupture, block shear and edge tear-out. Block shear depends on the bolt group's geometry rather than on the bolts — so adding a bolt to a crowded connection can make it weaker.
EitherBolt capacity
OrPlate capacity
10 factors weighed
Design establishes what the anchor should be capable of, against several failure modes of which a concrete one usually governs. Proof testing establishes what was achieved in the concrete that is there — because a post-installed anchor's capacity is created on site, and hole cleaning is the largest variable.
EitherDesign calculation
OrProof-load testing
10 factors weighed
Cooling the mix controls how fast it sets — placing time, cold joints, water demand and ultimate strength. Protecting the surface addresses evaporation, which is dominated by WIND rather than temperature. A mild windy day can be more hostile than a hot still one.
EitherCooling the mix
OrProtecting the surface
10 factors weighed
In a thick section hydration heats the core far above ambient while the surface cools to the air, and the crack risk is the DIFFERENCE between them. So the remedy is to insulate the surface rather than cool it — and stripping formwork early in cold weather can crack a mass pour within hours.
EitherInternal thermal gradient
OrSurface curing and protection
10 factors weighed
Covering, draining and mounting things on the fifth elevation. Slope and access decide more of these than appearance does — several options here simply cannot be installed below a certain pitch.
Shingles are the cheap, forgiving, any-roofer default with a shorter life. Metal costs more up front, demands better detailing, and then mostly outlives the question.
EitherMetal panels
OrAsphalt shingles
10 factors weighed
Both hinge the slope partway up so the upstairs walls stand rather than lean, and in section they are near-cousins. The gambrel breaks on two sides and leaves the building's two ends as ordinary vertical walls; the mansard breaks on all four and leaves no wall anywhere on the building. On a compact or squarish plan the barn form ends up with more usable floor for a fraction of the framing, and only once the building gets long does the mansard's steeper face win that back — which means the mansard's premium is mostly buying elevations rather than headroom, and whether you need those elevations is the whole question.
EitherGambrel (barn) roof
OrMansard roof
9 factors weighed
A hip slopes on all four sides: it braces itself against wind from any direction and puts an eave over every wall, paid for in cut angles, capping and the attic it eats. A gable is two planes and two end walls — cheap, repetitive and roomy, with its one weakness standing vertical at each end.
EitherHip roof
OrGable roof
9 factors weighed
Asphalt is a sealed mat with its exposure built in, laid on a solid deck by any crew in town. Cedar is a ventilated assembly of solid wood that gets wet on purpose and survives by drying afterwards — so the deciding questions are rarely aesthetic. What your jurisdiction and insurer allow, whether the roof planes get sun and air, and whether the substrate can breathe will settle this before preference does.
EitherCedar shakes / shingles
OrAsphalt shingles
9 factors weighed
Weight usually decides this before climate does: clay barrel tile is among the heaviest coverings a house can wear and metal among the lightest, and the difference is a multiple rather than a margin — so on a re-roof the first question is what the framing already carries, not which roof you prefer. Past that gate the two are opposites in a useful way. Tile is a brittle, inert shading layer over an underlayment that does the real waterproofing, so its service life is the hidden layer's and its mid-life job is a lift-and-relay. Metal is one coated skin that is both the barrier and the wear surface, so it is renewed rather than relaid, and its enemies are impact dents, coating age and salt rather than breakage.
EitherClay barrel tile
OrMetal panels
9 factors weighed
EPDM is one cured rubber sheet bonded cold, so a small roof can finish with no seam in the field at all and every remaining risk sits at the edges. Torch-applied modified bitumen is two plies of narrow rolls welded with a flame, so it carries far more lap but also a second waterproofing layer and a surface that takes abuse. What the deck is made of, and who has to work near the flame, usually settles this before durability gets a vote.
EitherEPDM rubber membrane
OrTorch-applied modified bitumen
9 factors weighed
Slate is split stone hung on nails that seals to nothing and stays dry on overlap alone; asphalt is a saturated mat bonded course to course into a skin on a continuous deck. The century is real, but it belongs to good slate, on a structure built to carry stone, fixed with metal chosen to outlast it. Three questions settle this before taste gets a vote: what the roof was framed to hold, whether anyone else controls what goes on it, and how many more times you expect to pay for the scaffold.
EitherNatural slate
OrAsphalt shingles
9 factors weighed
One decision, repeated everywhere the roof is held down: does the fixing sit under the seam or straight through the face? Standing seam leaves no holes in the water plane and lets the panel move; corrugated is cheaper, simpler and repairable by anybody, on the condition that every fastener's washer is a wear item with a date on it. What is under the roof, and whether somebody will honestly go back up there, decides this more often than the panels do.
EitherStanding seam (concealed clip)
OrCorrugated (exposed fastener)
9 factors weighed
Both proposals are load questions, but only one of them has a way out. An array the structure refuses can be fixed down mechanically and shed most of its ballast; a green roof the structure refuses can only get shallower, until the depth stops supporting anything alive. Where the membrane sits in its life decides nearly as much, because burying waterproofing under a permanent planted assembly is a decision that only makes sense on a roof that has just been laid.
EitherVegetated green roof
OrBallasted solar array
9 factors weighed
A drain takes the water down through the building; a scupper pushes it out through the parapet. Drains can sit anywhere in the field, so the taper runs stay short and nothing appears on the elevation — but the leader has to find a route past everything below it. Scuppers cost an opening in a wall and a piece of metal, and on most roofs they end up being the secondary path rather than the alternative to it.
EitherInternal roof drains
OrThrough-wall scuppers
9 factors weighed
Built-up roofing spreads the risk across several plies and pays for it in weight, time and hot work. Single-ply concentrates the risk into seams and details and pays for it in speed, lightness and the fact that those seams can be tested. The deck's load capacity and the complexity of the detailing usually decide it.
EitherBuilt-up roofing (BUR)
OrSingle-ply membrane
8 factors weighed
Both are heavy and both outlast the building's other finishes by a wide margin. Slate is inert and graded by expected life; clay is fired and its frost resistance is the property that decides whether it survives a hard winter. The roof's pitch and the structure's capacity settle it before taste does.
EitherClay tile
OrNatural slate
8 factors weighed
Ventilation attacks the cause — a roof deck warm enough to melt snow. The membrane attacks the consequence — water ponding behind a dam and finding its way in. Neither substitutes for the other, and neither works on a roof that leaks warm air, which is why air sealing is the first job on both lists.
EitherIce and water membrane at the eaves
OrAttic ventilation
10 factors weighed
No guard eliminates maintenance — the good ones convert scooping out leaves into brushing debris off the top, less often. The best-performing types can also shed water over the front in a downpour. And if the gutter overflows when clean, the fault is capacity or fall, not leaves.
EitherGutter guards
OrRegular cleaning
10 factors weighed
Tapered insulation creates the primary fall across a whole roof and gets thick at the high end. A cricket is a local diverter around an obstruction. Most roofs need both — and the fall that matters is the one left after the structure deflects, not the one on the drawing.
EitherTapered insulation
OrFramed crickets
10 factors weighed
A green roof retains — water is held and evaporated, so volume never reaches the drain. A blue roof attenuates — it delays discharge through a restricted outlet without reducing volume. A peak-flow limit needs attenuation; a volume target needs retention. And a saturated green roof retains almost nothing.
EitherGreen roof
OrBlue roof
10 factors weighed
The balanced load is uniform and modest; a drift is a local pile several times deeper, and it forms in predictable places — against a higher wall, behind a parapet or a plant screen, in a valley, at a roof step. A roof adequate under the balanced load can fail under the drift.
EitherBalanced snow load
OrDrift surcharge
10 factors weighed
A standing seam roof is attached by clips that let the panels slide, because metal moves substantially with temperature. A snow guard fixed through the panel pins it and destroys that. The resolution is seam-clamped guards that grip the rib without penetrating, so the whole assembly moves with the roof.
EitherSnow guards
OrThermal movement
10 factors weighed
Wind uplift is far higher at corners and edges than in the field, so one pattern is always wrong somewhere — under-fastened at the corners or wasteful everywhere else. And a corner failure is progressive: once the wind gets under the covering it peels the roof rather than damaging a corner.
EitherZoned to the uplift pressure
OrOne uniform pattern
10 factors weighed
The vertical skin and the holes in it. Every option here has to keep bulk water out, let vapour leave, and survive the sun on one elevation while staying damp on another.
Lap siding runs across the studs, so the frame the house already has is its nailing base and the choice genuinely is about appearance. Board and batten runs the same way the studs do and crosses none of them, so true boards have to be given something horizontal to fasten to — and if the wall is a drained, vented cavity, the furring that drains and vents it runs the wrong way for that. The vertical look is a legitimate reason to choose it. It is just a decision made behind the cladding, at the moment the sheathing is exposed, rather than in front of it.
EitherBoard and batten
OrHorizontal lap siding
9 factors weighed
Brick is an anchored veneer: it stands on its own ledge behind an air space and is only tied back for wind. Manufactured stone is adhered: it has no support of its own and hangs on the bond. Whether the wall already exists, and how much of the elevation is corner rather than field, settles this more often than the look does.
EitherBrick veneer
OrManufactured stone veneer
8 factors weighed
The trade rule is a height limit, and the height limit is a stand-in for the real test: does one continuous run of framing have to cross a floor line? If it does, it is a curtain wall at any budget, because only a curtain wall is anchored to the slab edge and detailed to absorb what the structure does there. If it does not, the answer is not automatic either — it falls out of the manufacturer's span chart at your design wind pressure, and out of how much water the space behind the glass can tolerate.
EitherCurtain wall
OrStorefront system
9 factors weighed
Seamless is the coating's headline and it is not the thing that decides this, because neither system fails in the field of the wall — the sheet fails at its laps, fasteners and openings, and the coating fails at its film build and the same openings. What actually separates them is that one is draped and one is bonded, and that one goes on in any weather while the other needs a dry substrate, a temperature and a cure window. Substrate, air-tightness target, weather window and whether there is a rainscreen cavity decide it far more often than the seam count does.
EitherMechanically fastened house wrap
OrFluid-applied weather barrier
9 factors weighed
Paint is a film a few thousandths of an inch thick whose whole performance is its grip on the board underneath — it has no structural opinion and it reaches nothing behind the cladding. So this is not a budget question first. Fade, chalk, dirt and a dated colour are coating conditions and paint is the right instrument for all four. Peeling that comes back, soft boards and failure clustered on one wall are the building talking about water, and a coating cannot answer that. Probe the boards before you price anything.
EitherRepaint the existing siding
OrReplace the siding
9 factors weighed
EIFS is the only one of the two that insulates, and it pays for that with a soft face and a total dependence on flashing, sealant and drainage. Three-coat stucco is hard, heavy and noncombustible, cracks where cement always cracks, and leaves the insulation problem to somebody else.
EitherTraditional three-coat stucco
OrEIFS (synthetic stucco)
9 factors weighed
Vinyl hangs loose on purpose — slotted fixings, a proud nail head, panels free to slide — and it is the lightest, fastest and least demanding cladding on the truck. Fiber cement is nailed tight into framing, weighs what a board weighs, cuts under a regulated dust standard, and arrives either finished at the factory or wanting paint. Neither is simply better. What settles it is usually a fire or separation gate, what your elevations are exposed to, and the honest answer to whether anyone will paint this house again in fifteen years.
EitherVinyl siding
OrFiber cement siding
9 factors weighed
Hot and draughty are two problems, not one. Film changes the optics of a glass surface and is a real answer to solar heat; draught lives in the frame joints where nothing stuck to the glass can reach it. The condition of your frames and sealed units decides first — then whether the complaint is a July one or a January one.
EitherApplied window film
OrReplacement windows
9 factors weighed
AAC insulates, is light enough to lay one-handed and is cut with a saw — and it is weak, thirsty and takes special fixings. Dense block is strong, heavy and a poor insulator. The thin-bed joint is the underrated part: it removes the mortar thermal bridge that gives back much of an insulating block's advantage.
EitherAAC (aerated) block, thin-bed
OrDense concrete block, conventional mortar
8 factors weighed
Both are applied over lath on a drainage plane, and neither is the waterproofing — the barrier behind them is. They fail the same way, at the base, when water that got in cannot get out. Stucco cracks and is patched; veneer debonds and falls off, and it is heavy enough for that to matter.
EitherStucco / cement render
OrAdhered stone veneer
10 factors weighed
Mass is predictable and expensive per decibel: roughly six for each doubling. Decoupling is far better value and can be destroyed by one wrong screw. Below a few hundred hertz only mass works. And before either, seal the perimeter — one per cent of open area caps a wall near STC 20 whatever else is in it.
EitherAdded mass (mass-loaded vinyl, extra board)
OrDecoupling (resilient channel or clips)
10 factors weighed
A drop ceiling makes everything above it permanently accessible and costs height to do it. Drywall looks finished and makes the same services reachable only by cutting. The acoustic difference is not what the tile marketing suggests: absorbing sound in a room and stopping it crossing over a partition are different properties.
EitherDrywall ceiling
OrSuspended (drop) ceiling
10 factors weighed
Paint is cheap, fast, touches up and is painted over when you tire of it. Paper gives pattern and texture nothing else can, conceals hairline cracks that paint reveals, and is bought by the roll but consumed by the drop — so the pattern repeat, not the price per roll, decides what the wall costs.
EitherPaint
OrWallpaper
10 factors weighed
Flashing is a shingled system: every lap goes over the one below, or the flashing directs water into the wall. Membrane conforms to any shape and seals around fasteners; metal holds its shape and carries a drip that throws water clear. Most openings need both, doing different jobs.
EitherSelf-adhered membrane
OrFormed metal
10 factors weighed
Sealant suits narrow gaps and joints that move, and it needs the right depth — a bead bonded to three sides cannot stretch. Foam fills wide voids nothing else reaches and exerts real pressure as it cures, which is why a standard foam around a window can bow the frame.
EitherCaulk / sealant
OrExpanding foam
10 factors weighed
A horizontal overhang shades by sun altitude — high in summer, low in winter — which is ideal on an equator-facing wall and useless on east and west, where the sun is always low. And a fixed device treats two days with the same sun angle identically, however different the weather.
EitherFixed overhang
OrAdjustable louvres
10 factors weighed
Transmission adds on energy weighted by area, so a facade performs like its weakest element. A wall is usually far better than the window in it — which means upgrading the wall first is money on the element that was not the problem. And a sealed unit's gap is sized for heat, not sound.
EitherAcoustic glazing
OrTreating the wall
10 factors weighed
Plaster is monolithic, harder and heavier — better against impact and measurably better against sound, because transmission loss follows mass. Board is faster, cheaper, drier and more predictable. They are not interchangeable at a junction, which matters on every renovation.
EitherThree-coat plaster
OrDrywall (plasterboard)
10 factors weighed
A shaftwall is erected entirely from one side, which is what makes it possible around a lift shaft or a riser where the far face is unreachable. It is a tested assembly, so its rating belongs to the exact combination of stud, liner, board and detailing — substituting an equivalent component does not carry the rating across.
EitherShaftwall system
OrConventional fire-rated partition
10 factors weighed
In a captured system the glass is held by a pressure plate and cap and the sealant weatherproofs. In structural silicone glazing the sealant IS the structure, carrying wind load for the building's life — so the bite width is calculated, the bonding is a factory operation, and adhesion is tested on the actual materials.
EitherStructural silicone glazing
OrCaptured (mechanically retained)
10 factors weighed
U-factor is conduction, and lower is better everywhere. SHGC is the share of solar energy that gets in, and lower is better only where cooling dominates — in a heating climate it throws away free winter heat. And SHGC is an orientation question, so one whole-house spec is always a compromise.
EitherU-factor
OrSolar heat gain coefficient
10 factors weighed
Ties restrain the veneer laterally against wind and carry essentially none of its weight. Shelf angles carry the weight into the structure at intervals. The soft joint under the angle is what makes that work — mortared solid, the angle relieves nothing and the wall spalls and bows.
EitherShelf angles
OrWall ties
10 factors weighed
A penetration is a static opening around something passing through. A joint is a gap between elements that moves, so its system is tested for a movement capability and a cycle count as well as for fire resistance. A penetration product in a joint passes inspection and has no movement rating at all.
EitherJoint firestopping
OrPenetration firestopping
10 factors weighed
Adhesive is never used instead of fastening. It bonds the board to the stud continuously, which permits reduced fastening in the field while the perimeter is screwed as normal — fewer fasteners means fewer pops. It is not permitted in every assembly, and rated construction is fastened as tested.
EitherScrews alone
OrAdhesive plus screws
10 factors weighed
A standard mesh reinforces the base coat against cracking from movement, which is its real job, and resists impact barely at all. Since impact happens in identifiable zones — ground level, entrances, service areas — the answer is a heavier mesh there and standard elsewhere. Either way it must be fully embedded.
EitherStandard mesh
OrImpact-resistant mesh
10 factors weighed
Depth makes the cavity a drainage path; opening area at the base and head makes it a drying one. A cavity with depth and no openings drains and stays damp; one with openings and no continuous depth does neither. Both depend on continuity, and horizontal furring is what interrupts it.
EitherCavity depth
OrVentilation opening area
10 factors weighed
A double stud wall decouples structurally, so there is no rigid path to short-circuit and its performance depends on geometry rather than workmanship. Clips decouple through a component and cost almost no depth — and one over-long screw defeats them, invisibly. Both are limited by the weakest path in the assembly.
EitherDouble or staggered stud
OrResilient clips on a single frame
10 factors weighed
Dead load is the weight of glass the mullion carries to its anchors — a real check that rarely sizes the member. Wind deflection does, because glass is brittle and its seals tolerate little frame movement. And deflection scales steeply with span, so storey height drives facade depth.
EitherDead load
OrWind deflection
10 factors weighed
A facade's performance is quoted for the vision glazing, and the condensation happens at the spandrel — a shallow cavity at the floor edge, cold, bridged by framing and slab, and the part nobody looks at. The mechanism is usually warm indoor air leaking into it rather than the insulation being inadequate.
EitherSpandrel condensation risk
OrVision glass U-factor
10 factors weighed
Absorbers remove energy and reduce reverberation, which suits a room where sound is sloshing around. Reflectors redirect it — and early reflections reinforce a talker rather than blurring them. Over-absorbing a lecture room produces a space that is quiet, dead and harder to listen in.
EitherReflectors
OrAbsorbers
10 factors weighed
Slowing heat and stopping air, which are two different jobs that get bought as one product. The installed result differs from the number on the bag more here than anywhere else on the site.
Blown-in wins in open attics because it fills what batts bridge; batts win in open walls and anywhere you need the insulation to stay put and be lift-able.
EitherBatts (rolls)
OrBlown-in (loose fill)
10 factors weighed
Same cavity, same arithmetic, and in an ordinary dry stud bay the cheap batt does the job. Mineral wool earns its premium in the minority of cavities with a second job — fire, sound, water, or a position a limp batt sags out of.
EitherMineral wool batts
OrFiberglass batts
9 factors weighed
These are not two versions of the same measure. The foil deflects radiant gain at the roof deck and does nothing in winter; depth resists conduction through the ceiling in both seasons. The settled depth already on your attic floor decides most of it, and ducts in the attic decide the rest.
EitherAttic radiant barrier
OrBlown-in insulation
9 factors weighed
This is not a contest between two insulation products. It is a decision about which surface is the boundary of the house — the sloped deck above or the flat ceiling below — and the sealed attic's one reliable prize is bringing the ducts and the air handler indoors. If they are up there and staying there, that trade is the whole argument. If they are not, the deck is a larger, permanent, un-stageable surface to buy for very little in return.
EitherSealed attic (foam at the roof deck)
OrVented attic (insulation on the floor)
9 factors weighed
Batts slow conduction and nothing else — air walks through them, and they reach the number on the bag only when fitted perfectly. Foam brings the air seal with it, and charges for it in money, in permanence and in a cure nobody can inspect. Whether anyone is going to build and test an air barrier by other means decides this more than either product does.
EitherSpray foam
OrFiberglass batts
9 factors weighed
For the same installed resistance both break the stud bridge identically, so the contest is not about insulating. Foam gives that resistance in less depth and can be the water and air control layer in one taped plane; mineral wool lets the wall keep drying outward and has no thickness below which it becomes a hazard. What is on the inside face of the wall, and how much depth you can actually detail at the windows, decide it far more often than the R chart does.
EitherRigid foam board
OrMineral wool board
9 factors weighed
Cavity fill is cheap, fast and invisible, and it is only appropriate where the cavity is suitable and the wall is not severely exposed — because filling a cavity removes the gap that was stopping water crossing it. External insulation works on any wall, removes nearly all the thermal bridging, and costs its money in details rather than boards.
EitherExternal wall insulation
OrCavity wall insulation
8 factors weighed
Diffusion moves vapour through materials, slowly. Air leakage moves moist air bodily through holes, and carries one to two orders of magnitude more water. Air sealing is therefore the higher-value job nearly everywhere — and a vapour barrier on the wrong side traps moisture instead of excluding it.
EitherVapour barrier
OrAir sealing
10 factors weighed
Envelope leaks are driven by wind and the stack effect; duct leaks are driven by a fan, at far higher pressure, so the same size hole passes much more air. Ducts outside the conditioned space are the priority — they deliver conditioned air straight outdoors and pull attic air into the supply.
EitherSealing the ducts
OrSealing the envelope
10 factors weighed
Heat loss through a wall runs on parallel paths, and parallel paths are dominated by the best conductor. So once the insulated field is good, the loss has moved into the studs, joints and junctions — and none of those improve when the cavity gets thicker. Continuous insulation interrupts every path at once.
EitherMore insulation in the field
OrInterrupting the bridges
10 factors weighed
Z-furring is a continuous metal line through the insulation — exactly the bridge the insulation was installed to remove — and the penalty can be a large fraction of the nominal value. Clips break it into point fixings with a thermal break. Clip spacing is engineered from cladding weight and wind load.
EitherClips and rails
OrZ-furring
10 factors weighed
A ground barrier cuts off evaporation from the earth, which is the dominant moisture source and the cheapest fix available. Encapsulation goes further: it seals the vents, insulates the perimeter and brings the space inside the envelope — which is what stops warm humid summer air condensing on cool surfaces.
EitherFull encapsulation
OrGround vapour barrier alone
10 factors weighed
The coldest strip of a well-insulated ceiling is directly over the exterior wall, where insulation is squeezed between the plate and the sheathing and a vent path must also fit. A raised heel creates depth for both; baffles keep the air channel clear but cannot create depth that is not there.
EitherRaised-heel truss
OrBaffles and compressed insulation
10 factors weighed
Plant that spends energy to move heat or air. These are the comparisons where running cost dwarfs purchase price, and where sizing wrong is worse than choosing wrong.
A tank runs out of hot water but never out of flow; a tankless runs out of flow but never out of hot water. Which limit your household hits first is the whole decision.
EitherTankless (instantaneous)
OrStorage tank
12 factors weighed
In cooling they are the same machine. The heat pump adds a reversing valve and becomes your heating too — the question is what your winters and your existing heating make of that.
EitherHeat pump
OrAir conditioner (cooling-only)
12 factors weighed
The fan moves more air and will read cooler on a July afternoon — but it pulls hard enough to choose its own make-up air, and a leaky ceiling below is the path it takes. The ridge vent pulls too gently to do that, and gets its capacity from ridge length the roof may not have. How much continuous ridge you own, and how sealed the ceiling under it is, decide this before preference does.
EitherContinuous ridge vent
OrPowered attic fan
9 factors weighed
The decision is made by your heat source, not by your preference. A radiator needs hot water and gives it back fast; a floor needs barely-warm water and gives it back slowly over an enormous area. With a boiler the radiator is hard to beat; with a heat pump the floor is the natural partner — and a heat pump driving old radiators is the case that disappoints.
EitherRadiators and baseboard convectors
OrUnderfloor heating loops
9 factors weighed
A furnace produces the same output at minus twenty as at plus ten; a heat pump produces less exactly when you need more. That asymmetry — not efficiency, not fuel price — is what sets the sizing rule, the balance point and whether a backup is needed at all.
EitherAir-source heat pump
OrGas or oil furnace
9 factors weighed
Batteries win the short outage: instant, silent, indoors, no fuel. Generators win the long one, because a store runs out and a fuel supply does not. The decision is about the outages your area actually has — and a small battery in front of a generator is often better than a larger version of either.
EitherStandby generator
OrBattery bank and inverter
8 factors weighed
A stove heats the room it is in, on your attention, with fuel you handle. Central heating heats everywhere, unattended, on a thermostat. The decision is rarely either/or — and the one thing worth getting right about a stove is that it should be SMALLER than instinct suggests, because a throttled stove is a dirty stove.
EitherWood-burning stove
OrCentral heating system
8 factors weighed
Rigid duct has low resistance, lasts, can be cleaned and takes time and skill to install. Flex is fast, cheap, quiet and absorbs misalignment — and it only performs as published when it is pulled taut, which it usually is not. The standard answer is a rigid trunk with short, taut flex runouts.
EitherRigid sheet metal duct
OrFlexible duct
8 factors weighed
Insulation delays; trace heating prevents. A still pipe with only insulation reaches ambient eventually, so insulation alone protects against a short cold spell and nothing longer. Trace heating protects indefinitely and needs insulation over it to be affordable — the design question is how to split the duty, not which to choose.
EitherPipe insulation
OrElectric trace heating
8 factors weighed
An electric mat adds millimetres, installs in an afternoon and costs the most expensive energy there is. A wet system adds tens of millimetres and a manifold, and on a heat pump it runs at a fraction of the cost. Use the mat to make a floor warm; use the wet system to heat a house.
EitherElectric heating mat
OrWet underfloor loops
10 factors weighed
The rule of thumb is not just imprecise, it is biased high — it was calibrated on leaky, poorly insulated houses. Oversizing costs comfort rather than money: dehumidification depends on runtime, so a unit that satisfies the thermostat in eight minutes leaves the house cold and damp.
EitherLoad calculation from the building
OrArea-based rule of thumb
10 factors weighed
Exhaust-only is one fan and cheap. It also depressurises the house and takes make-up air from wherever it can — a crawl space, a flue, a wall cavity. Balanced ventilation supplies as much as it extracts, filters what comes in, and recovers most of the heat that would otherwise leave with it.
EitherBalanced ventilation with heat recovery
OrExhaust-only ventilation
10 factors weighed
Ampacity is the safety limit: the conductor must not overheat, and the breaker protects it. Voltage drop is a performance limit: the load must receive usable voltage at the far end. Take the larger of the two sizes — and remember that only the first one has anything that trips when it is wrong.
EitherSized for ampacity
OrSized for voltage drop
10 factors weighed
Evaporation is the dominant heat loss from an outdoor pool, and it happens at the surface. A cover stops most of it, which makes it the most effective heating intervention available. A heater without a cover replaces heat that is leaving as fast as it arrives.
EitherPool cover
OrPool heater
10 factors weighed
Off-grid sizing is set by the worst week of the year, not the average — so the battery bank and the array are both large and idle most of the time. Grid-tied storage only has to cover an outage, because the grid is the rest of the system. The comparison is autonomy, and it is expensive.
EitherOff-grid
OrGrid-tied with battery backup
10 factors weighed
Ventilation dries a building only when outdoor air holds less water than indoor air — in grams per kilogram, not relative humidity. That is true in winter and often false in summer, which is why ventilating a cool basement in July makes it damper. Find the source first; both are removing symptoms.
EitherDehumidification
OrVentilation
10 factors weighed
Propane holds around two and a half times the energy per unit volume and runs at a higher pressure, so every appliance needs a different orifice and regulator. It is also heavier than air, so a leak sinks and pools rather than rising. Mains gas needs a connection; propane needs a tank and deliveries.
EitherNatural gas
OrPropane (LPG)
10 factors weighed
Sanitiser cannot reach what circulation does not bring to it, and a filter removes only what passes through it. Before adding anything, check the water is actually turning over. And on the chemistry side, chlorine's effectiveness depends on pH — so high pH makes the same measured level do far less work.
EitherCirculation and filtration
OrChemistry
10 factors weighed
Bundled conductors derate because they cannot shed heat, so a cable in a spaced single layer on a tray carries more than the same cable in a full conduit. Tray costs a lot per metre and almost nothing per added circuit; conduit is the reverse. Tray needs cable rated for it and offers no mechanical protection.
EitherCable tray
OrConduit
10 factors weighed
A silencer attenuates noise travelling inside the duct toward a grille. Lagging stops noise breaking out through the duct wall into the room the duct passes through. Different paths, opposite treatments — and a silencer adds pressure drop, so the fan works harder and becomes a noise source itself.
EitherDuct silencer (attenuator)
OrLagging the duct
10 factors weighed
Velocity sizing holds air speed constant and lets pressure loss fall where it falls. Equal friction holds pressure loss per metre constant and lets velocity taper along the run. Equal friction is the default for ordinary systems — and neither balances an asymmetrical layout on its own.
EitherVelocity method
OrEqual friction method
10 factors weighed
Waiting is a distribution problem — the pipe run is full of cold water and you are pushing it out. Running out is a capacity problem. Recirculation fixes the first and slightly worsens the second, because a loop is a continuous heat loss. Decide which fault you have before buying either.
EitherRecirculation loop
OrMore recovery or storage
10 factors weighed
A fan cools people, not rooms — it speeds evaporation and convection from skin, which feels like several degrees while changing air temperature not at all. So it does nothing in an empty room, and nothing once the air is near skin temperature. The efficient answer is both: cooling set higher, with a fan running.
EitherCeiling fan
OrAir conditioning
10 factors weighed
An expansion tank absorbs the volume increase when water is heated in a closed system, so pressure does not rise enough to lift a relief valve. A pressure tank stores usable water so the pump does not start at every tap. Same appearance, same bladder, different jobs — and both fail silently when the pre-charge is wrong.
EitherThermal expansion tank
OrWell pressure tank
10 factors weighed
Structure-borne noise travels through the frame, and no treatment in the airstream touches it. An isolator works by static deflection — one that barely compresses is barely isolating, and one chosen without knowing the running speed can land near resonance and make things worse.
EitherIsolating the plant
OrSilencing the duct
10 factors weighed
An economiser cools with outdoor air instead of a compressor, and the right test is total enthalpy — heat and moisture together — not temperature. In a humid climate, cool saturated air carries more energy than warmer dry return air, so a dry-bulb economiser can increase the load it was meant to reduce.
EitherEconomiser (free cooling)
OrMechanical cooling
10 factors weighed
Fixture units give the design flow, with diversity built in so the figure is far below the sum of the fixtures. Friction loss then checks whether enough pressure survives the journey. A pipe sized on flow alone can be perfectly adequate in capacity and still deliver nothing useful at the far end.
EitherFixture-unit method
OrFriction-loss calculation
10 factors weighed
An EV charger is an unusually flexible load: the car is parked far longer than it needs to charge, so a charger that backs off during the evening peak still finishes overnight. That is what makes load management a real alternative to an expensive service upgrade — and the calculated load is often well above the measured one.
EitherLoad management
OrService upgrade
10 factors weighed
The trip rating is the current at which a breaker opens to protect its circuit, chosen from the load and conductor. The interrupting rating is the fault current it can safely break, set by the supply rather than the load — so a small breaker close to a large transformer can be the under-rated one.
EitherTrip (ampere) rating
OrInterrupting rating
10 factors weighed
A damper balances by adding resistance to the easy paths until they match the hard one — it never reduces the hard path, so the fan still fights the worst branch and everything else is throttled to match. Sizing so branches start comparable reduces what has to be thrown away; dampers then trim rather than compensate.
EitherBalancing with dampers
OrSizing the ducts to balance
10 factors weighed
Fill is a percentage of area and is identical on a short run and a long one. Pulling tension grows with length and, far more sharply, with bends — each bend multiplies the tension entering it rather than adding to it. A run within its fill limit can still be unpullable, and the damage is to the insulation.
EitherFill percentage
OrPulling tension
10 factors weighed
A circle encloses an area with the least perimeter, and duct friction acts at the wall — so round costs less pressure, less metal and less insulation. Rectangular exists because ceiling voids are shallow, and its penalty grows with aspect ratio. Size it by equivalent diameter, not by equal area.
EitherRound duct
OrRectangular duct
10 factors weighed
Working clearance is a safety requirement with hard dimensions, including the number and position of exits, and the space must stay clear. Transformer heat is a ventilation requirement, and the losses are substantial. Both govern, they compete for the same area, and both are usually discovered after the plan is fixed.
EitherWorking clearance
OrTransformer heat load
10 factors weighed
Both, and they are different corrections. Derating says the system delivers less than its nameplate over a long run, worsened by vertical lift. Charge adjustment says the extra pipe volume must be filled, at a stated amount per unit length. Both use EQUIVALENT length, so fittings count.
EitherCapacity derating
OrCharge adjustment
10 factors weighed
A PRV holds static pressure down continuously. An arrestor absorbs a transient spike caused by a fast-closing valve stopping moving water — and that spike depends on velocity and closing time, not on static pressure. A system at normal pressure can hammer, and a PRV will not stop it.
EitherPressure-reducing valve
OrWater hammer arrestor
10 factors weighed
Hangers stop the pipe sagging; loops let it grow. They conflict, because supports restrain — which is resolved by distinguishing anchors, which fix the pipe and decide where movement goes, from guides, which carry it while letting it slide. Anchors without guides buckle; guides without anchors walk.
EitherHanger spacing
OrExpansion loops
10 factors weighed
A large exhaust fan removes air and an equal volume must return. Supplied deliberately, the kitchen works; not supplied, the building goes negative and draws replacement air through whatever paths exist — which can include an appliance flue. The fan also fails to reach its rated flow, so the hood stops capturing.
EitherHood exhaust rate
OrMake-up air
10 factors weighed
Normal lighting is designed for a task: an average illuminance with uniformity and glare control. Emergency lighting is designed for evacuation: a minimum along the escape route's centre line, with the supply gone, for a stated duration — and it is located by hazard rather than by area.
EitherEmergency escape lighting
OrNormal illuminance design
10 factors weighed
String sizing is a voltage problem bounded by temperature, and module voltage RISES as it gets colder — so the limiting case is the coldest morning, not a summer afternoon. Inverter sizing is an energy problem, and it deliberately lets the array exceed the inverter's rating because the peaks it clips are worth little.
EitherString sizing
OrInverter sizing
10 factors weighed
The liner contains combustion products and must be free to expand, because bedding it rigidly cracks it. The clearance handles heat conducted through the assembly, which a sound liner does nothing about — and wood held near a warm chimney chars over years until it ignites at a temperature that was once safe.
EitherLiner and firebrick expansion
OrClearance to combustibles
10 factors weighed
Air supplied to a room has to leave it at the same rate or the room pressurises and the supply chokes. The supply is designed and commissioned; the return path is usually assumed — and a closed door with no return turns a correct supply into a room that never reaches temperature.
EitherReturn air path
OrSupply air sizing
10 factors weighed
What you walk on, and what it demands of the subfloor beneath it. The substrate you already have rules out at least one option in most of these before taste gets a vote.
Tile wins on permanence and heat; LVP wins on speed, comfort and forgiveness. The substrate you have usually decides before taste does.
EitherLuxury vinyl plank
OrCeramic / porcelain tile
10 factors weighed
Tile buys you the local repair — a square lifts out, and a wetting or a cable pull stays a square. Broadloom buys the soft, quiet, seamless field a room actually feels. Awkward plans and damp slabs push hard toward tile; a large dry rectangle that fits the roll width pushes back.
EitherModular carpet tile
OrBroadloom roll carpet
9 factors weighed
Carpet is warm, quiet and forgiving, and it keeps everything it absorbs. Vinyl plank is wipeable, repairable and hard, and it keeps nothing. Since bedrooms and a living room are asking for opposite things, the useful question is not which floor but which room.
EitherBroadloom carpet
OrLuxury vinyl plank
9 factors weighed
Same floor, same wear, same lifespan — this is a decision about cost, risk and appearance, not performance. A straight lay feeds its own offcuts back into the next row and its quantity tracks the area. Herringbone cuts nothing in the field and everything at the edge, so its cost follows the boundary and the block count instead — which makes the premium worst in the small cut-up room, and best in the big square one where the pattern also has the most to show.
EitherHerringbone / chevron
OrStraight plank lay
9 factors weighed
Both are vinyl and both shrug off water as a material, but only one of them can be made into a continuous tray that turns up the wall. Sheet wins containment and loses on looks and repair; plank wins looks and repair and hands you an open joint at every wall. How wet the room genuinely gets — splashed and wiped, or drained and mopped — decides it long before taste does.
EitherSheet vinyl
OrLuxury vinyl plank
9 factors weighed
A screed gives you depth: cover over pipes, a level over a rough deck, mass for acoustics. A compound gives you flatness in a few millimetres over something already at the right height. They are not competitors, and the failure in both directions is trying to make one do the other's job.
EitherSand-cement or anhydrite screed
OrSelf-levelling compound
8 factors weighed
Terrazzo is a material: aggregate through its thickness, reground rather than replaced, and good for generations. Epoxy is a coating: fast, chemically resistant, and finished when it wears through. The slab's moisture and the programme usually decide it before appearance does.
EitherTerrazzo
OrEpoxy resin floor
8 factors weighed
Backer board gives tile a stable substrate to bond to; crack isolation decouples tile from movement in the substrate below. Neither stiffens a floor — deflection is a framing question answered before either is bought, and a floor that fails it will crack tile whatever is underneath.
EitherCrack isolation membrane
OrCement backer board
10 factors weighed
A floating floor is an unfixed plate that grows and shrinks. The perimeter gap gives that growth somewhere to go at every edge; transition strips keep each area short enough that the growth fits in the gap. Omit either and the floor tents — because movement is proportional to length.
EitherPerimeter expansion gap
OrTransition strips
10 factors weighed
Drives, patios, fences and the ground they sit on. Drainage and frost do the deciding here; the surface you see is the part that matters least.
Concrete is monolithic: cheaper per area, faster to place, and it cracks as one piece. Pavers are modular: dearer up front, repairable a unit at a time, and their real cost is the base underneath.
EitherPoured concrete
OrPavers
10 factors weighed
The ground decides first: decks bridge slopes and bad ground that patios would fight expensively. On flat ground, the patio's near-zero maintenance meets the deck's warmth and height match.
EitherTimber deck
OrPaver patio
12 factors weighed
Gravel is the low-cost, self-repairing, DIY-able surface that asks for a rake and a top-up forever. Asphalt is the clean, plough-able, higher-cost surface on a clock that starts at sealing time.
EitherGravel
OrAsphalt
12 factors weighed
Concrete buys lateral stiffness, gravel buys drainage, and a fence asks for each in different places. Gates, corners and end posts carry a pull that never lets go and want the rigid collar; line posts on a permeable fence in ground that drains are gravel's home turf. What decides your run is the soil you are digging in, what the post is made of, and whether the load ever stops.
EitherPosts set in concrete
OrPosts set in compacted gravel
9 factors weighed
A French drain needs somewhere downhill to discharge and stops water reaching the structure at all; a sump works anywhere and accepts the water first. If you have the fall, intercept. If you do not, pump — and know that you have bought a mechanical system with a power supply and a failure mode.
EitherFrench drain, gravity outfall
OrSump pit and pump
8 factors weighed
A pipe conveys and does nothing else, in a trench. A swale conveys slowly, and because it is slow it also settles sediment and infiltrates — which is why it needs several times the cross-section and a strip of land. Where there is width, the swale does three jobs; where there is not, the pipe does one properly.
EitherGrassed swale
OrPiped storm drain
8 factors weighed
Rainwater is clean and arrives when it feels like it, so it is a storage problem that fails in a drought. Greywater arrives whenever the house is occupied and cannot wait, so it is a treatment problem that has to be used within a day. Match the source to whether your demand is seasonal or constant.
EitherRainwater harvesting
OrGreywater reuse
8 factors weighed
Permeable paving stores rainfall in its own sub-base and removes the drive from the drainage problem — at the cost of a deeper, graded build-up and a surface that must be swept or it clogs. Asphalt is cheaper and faster and sends every drop somewhere else, which is increasingly something you have to have permission for.
EitherPermeable block paving
OrAsphalt drive
8 factors weighed
Chain link is a tensioned system whose corners are the structure and whose openness makes wind almost irrelevant. A timber fence is a row of cantilevers whose footings are the structure and whose solid area is the load. They fail in different places, and the failure of a solid fence is usually the wind nobody counted.
EitherChain link fence
OrTimber picket or close-board fence
8 factors weighed
A ramp is passive, needs no power, never breaks, and is far longer than people expect — a metre of rise is twelve metres of slope plus landings. A lift fits where a ramp cannot and introduces a machine that will eventually be out of service on the only accessible route. Available length usually decides it.
EitherPlatform lift
OrRamp
8 factors weighed
Sod is an instant lawn at roughly ten times the material cost, laid in almost any growing weather. Seed is cheap, offers any cultivar you like, and has a narrow sowing window. They need opposite watering — deep and infrequent for sod, light and frequent for seed — and both fail on bad soil regardless of which you chose.
EitherSod (turf rolls)
OrGrass seed
10 factors weighed
Sloping needs room and generates spoil that grows with the square of the depth. Shoring needs engineering and grows in force with the square of the depth too. A trench box is a shield, not shoring: it protects the people inside it and does nothing for the ground or the building outside it.
EitherSloping or benching the sides
OrShoring or shielding
10 factors weighed
Crack filling keeps water out of the base, which is what destroys asphalt. Sealcoating is a surface film that resists UV, oxidation and fuel and adds no structural capacity at all. They are not alternatives: fill the cracks first, every time, or the sealcoat reflects through within a season.
EitherSealcoating
OrCrack filling
10 factors weighed
Spray covers area and suits turf; drip delivers at the root zone with almost no evaporation or wind loss and suits beds, hedges and trees. They apply water at rates an order of magnitude apart, so they can never share a zone — and spray only works when every head throws all the way to its neighbours.
EitherSpray and rotor heads
OrDrip and dripline
10 factors weighed
A silt fence is a perimeter control for thin sheet flow off a small area. A basin treats concentrated flow from a large one. Put a fence across a channel and it is overtopped or undermined, releasing everything it held. Neither removes clay, which is why erosion control upstream beats sediment capture downstream.
EitherSilt fence
OrSediment basin
10 factors weighed
Riprap is permanent armour for velocities vegetation cannot survive. A blanket is temporary, and its job is to hold soil and seed until the vegetation it protects becomes the permanent protection. Both fail at the same places — the upstream edge and the toe — and almost never in the middle.
EitherRiprap
OrErosion control blanket
10 factors weighed
Stain penetrates and wears away by erosion, so it is recoated after a clean. Paint forms a film, and on a horizontal surface water eventually gets behind it and it peels — which means stripping. The decision is close to one-way: you cannot stain over paint.
EitherDeck stain
OrDeck paint
10 factors weighed
A ladder is access, not a work platform: one hand holding on, a reach of about an arm either side, and nothing arresting a fall. A scaffold is a platform with guardrails and somewhere to put the work down. The honest test is duration, reach and what you are carrying — not what the job costs.
EitherScaffold
OrLadder
10 factors weighed
Cable railing keeps the view and is a tension structure — every cable pulls on the end posts, and their accumulated load is what people fail to design for. Balusters carry no tension, cost a fraction, and any carpenter can fit them. Both must pass the same sphere rule, and cable has to pass it while being pushed.
EitherCable railing
OrBalusters
10 factors weighed
Diversion is measured by weight, and inert material is heavy — so separating rubble alone moves the number further than separating every light stream. A mixed skip is easier on site and relies entirely on the sorting facility. Contamination is what turns a recoverable load into a disposed one.
EitherMixed skip
OrSource separation
10 factors weighed
Prime coat penetrates a granular base and binds its loose surface so asphalt has something to stick to. Tack coat is a thin bonding film between bound layers and penetrates nothing. Too much tack coat is worse than none — a thick film becomes a slip plane and the pavement delaminates.
EitherPrime coat
OrTack coat
10 factors weighed
A site that balances on drawing volumes usually does not balance in practice, because soil bulks when excavated and compacts differently when placed. And balance is irrelevant if the material cut is not suitable as engineered fill — which is a soils question, answered before the programme is priced.
EitherBalancing on site
OrImporting or exporting
10 factors weighed
Polymeric sand sets to lock the joints against washout and weeds, and it is essentially impermeable. Open-graded joint fill is the infiltration path of a permeable pavement — nearly all the water enters through those joints. Using the wrong one converts a drainage system into a solid slab.
EitherPolymeric sand
OrOpen-graded joint fill
10 factors weighed
A joint must transfer load or the far slab deflects alone, pumping water and fines out from under it. Interlock does that free while the crack stays narrow and fails as the joint opens. Dowels transfer shear through an unbonded bar that still lets the joint move — and a bonded or skewed dowel locks it instead.
EitherDowelled joints
OrAggregate interlock
10 factors weighed
Pedestals hold pavers on adjustable points over an open void, so a roof drains beneath them, the membrane stays reachable by lifting a paver, and the load is low. Bedding puts a continuous mass of aggregate on whatever is below. On a roof the first is usually right; at ground level the second is.
EitherPedestal-mounted pavers
OrPavers bedded on aggregate
10 factors weighed
Sump pumping removes water after it enters, so water flows through the formation into the dig — carrying fines, undermining the base and, in granular soil, causing piping and boiling. Wellpoints lower the table before excavation so no flow occurs. Both can settle neighbouring ground, which is a monitoring obligation.
EitherWellpoint dewatering
OrOpen sump pumping
10 factors weighed
Barrowing is limited by the person, and its productivity collapses with distance, gradient and soft ground. Machine haulage is limited by access rather than volume, and the cost of creating access can exceed the haulage. The answer is usually a hybrid: machine to a point near the work, barrow the last leg.
EitherBarrowing
OrMachine haulage
10 factors weighed
The cost is dominated by the exchange — delivery, collection and tipping — rather than by the container's size or the days it stands. So two small skips cost close to twice one, while a larger skip standing longer costs little more. Weight, access and permits are what override the arithmetic.
EitherA larger container
OrA longer hire on a smaller one
10 factors weighed
Crane capacity is the machine's rated lift at that radius, reduced by the rigging's weight. Sling leg tension is not the load divided by the legs — inclined legs carry more, and the multiplier grows sharply as the angle to the horizontal falls. A lift within the crane's rating can overload its slings.
EitherSling leg tension
OrCrane capacity
10 factors weighed
Separation keeps two layers from mixing and is chosen on strength and puncture resistance. Filtration passes water while retaining fines and is chosen on opening size matched to the soil. Use the wrong one and either the drain silts and blinds, or the fabric tears on the first pass of a lorry.
EitherSeparation geotextile
OrFiltration geotextile
10 factors weighed
Volume tells you how much material, and it is not the excavation's volume — soil bulks coming out and compacts going back. Lift count tells you how it goes in, and a compactor only densifies a limited depth beneath it. A trench filled in one go is loose through most of its depth whatever the plate weighed.
EitherBackfill volume
OrCompaction lifts
10 factors weighed
The tank is sized on volume, for retention time. The field is sized on what the soil can accept, and no tank changes that. The tank's real job is to protect the field — solids that carry over clog it, and a clogged field is replaced rather than cleaned.
EitherSeptic tank
OrDrain field
10 factors weighed
Weeds in a fabricked bed germinate in the mulch ON TOP of the fabric and root through it — so the fabric makes them harder to pull, not fewer. Mulch suppresses weeds by excluding light and improves the soil as it breaks down. Fabric's real job is separation under gravel, where nothing is planted.
EitherLandscape fabric
OrMulch depth
10 factors weighed
Fertiliser supplies nutrients at a known rate, and the rate that matters is nutrient per unit area — the bag's analysis converts to it. Compost supplies organic matter, with low and variable nutrients, and is the only one of the two that changes the soil's structure and water holding.
EitherFertiliser
OrCompost
10 factors weighed
Zoning is hydraulic: only so many heads can run at once at the pressure they need. Uniformity is how evenly the water lands — and because run time is set by the driest spot, poor uniformity is paid for in excess water applied to the whole zone rather than in a dry patch.
EitherZoning
OrDistribution uniformity
10 factors weighed
Stall count is what a layout is judged on; the design vehicle's swept path is what decides whether it works. Rear wheels cut inside the front through a turn while the front overhang swings out, so a long vehicle sweeps far wider than the aisle it needs on a straight — and the check belongs first, because the redo costs stalls.
EitherDesign vehicle turning path
OrStall count and layout
10 factors weighed
A published average cost per square metre is wrong for almost every real project, and wrong in a direction nobody can predict from the page: labour rates move by region and by month, access and substrate condition swing preparation more than the finish material does, and the quantity you need is the one part that can actually be calculated. So these pages say which side of the cost is structural — where labour dominates, where the hidden layer is, which option punishes a bad substrate — and leave the number to your quotes.
What each page is specific about instead: the failure mode of each option, what the substrate or the climate rules out before preference matters, the maintenance the choice commits you to, and the situations where one side simply cannot be used. Where a figure varies by jurisdiction, the page names what governs it rather than publishing a number that would be wrong somewhere.
Once the decision is made, the calculators give you the quantity, the trade guides cover the site work around it, and the methodology pages show the mathematics if you want to check the arithmetic yourself. To price both options properly, run each through Project Builder and compare two complete estimates rather than two unit rates.
These are guidance rather than specification. Local codes, the engineer of record and the manufacturer’s instructions govern wherever they differ, and several of the choices here are structural decisions that need signing off rather than looking up.