Field guides

Trade guides

The calculators give you a quantity. These explain the work around it — the order things happen in, the tolerances that matter, and the mistakes that only show up months later.

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Timber-framed house under construction with ladders, sawhorses and lumber

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382 guides

Structure and carpentry40 guides

Foundations
Choosing and Building a Base for a Garden Room
Slab, pads, ground screws or steel — chosen by the fall across the plot, the clay under it, the trees around it and the width of the side gate.
20 min read12 sections17 calculators2026-08-31
Carpentry
Building a Timber Deck
A carpenter's walk down the load path of a timber deck — footing, post, beam, joist, board — each member sized by what the one above hands down.
10 min read6 sections8 calculators2026-08-28
Carpentry
Building a Pergola
A pergola is read from underneath, so the rafter and purlin grids get settled against the yard's stock lengths before the first tail is cut.
19 min read9 sections13 calculators2026-08-31
Outbuildings
Founding and Anchoring a Shed or Pergola
A flat-pack kit settles everything except the runner grid under it, the post positions it has to land on, and the hold-down it ships without.
19 min read9 sections15 calculators2026-08-31
Structure
Building a Steel Mezzanine Deck
A whole structure squeezed into one bay of a running warehouse: slab, grid, deck span, bolt group and edge, in the order each one bites.
19 min read10 sections11 calculators2026-08-31
Carpentry
Building Closet Shelving From Lumber
A reach-in closet is bought in sticks and quoted in board feet, so the shelf run, cleats and rod get tallied twice before any order goes in.
17 min read10 sections10 calculators2026-08-31
Carpentry
Building Stairs That Pass Inspection
A one-millimetre layout error repeats once per riser, so control the whole flight from a single datum and prove the spread before the inspector arrives.
12 min read9 sections8 calculators2026-08-28
Mass timber
Building With CLT and Glulam
Mass timber erection is finish work: every CLT panel and glulam beam you set is the ceiling below it, so damage is permanent.
12 min read11 sections8 calculators2026-08-28
Structure
Checking Whether a Floor Will Take a Heavy Load
The load side is arithmetic anybody can do. The capacity side is a judgement about a floor nobody drew, and the two halves live in different documents.
17 min read10 sections12 calculators2026-08-31
Mass timber
Checking an Exposed Timber Beam
One glulam justified twice: full section with snow's duration factor, then the residual section an hour of fire leaves behind.
16 min read8 sections11 calculators2026-08-31
Stairs
Checking a Built Stair: Riser Tolerance and What Guards It
The tolerance sits between the tallest and the shortest riser in one flight, not on any single step. Measuring a finished stair, and judging its guard.
18 min read11 sections9 calculators2026-08-31
Structure
Checking Truss Shop Drawings
Forty-one sheets and one seal: what to read on a truss design drawing, from the load block to the plate callout, before the pack reaches the saw.
20 min read10 sections11 calculators2026-08-31
Carpentry
Choosing a Framed Exterior Wall Build-Up
Stud size and spacing, cavity insulation, vapour control, sheathing and cladding: what each choice changes in the order, and what it never does.
8 min read6 sections11 calculators2026-10-10
Carpentry
Cutting and Setting Rafters
A carpenter's field guide to rafter layout, treating every plumb, seat and cheek cut as one triangle solved from run and rise.
11 min read6 sections10 calculators2026-08-28
Structure
Designing a Roof for Snow
Snow does not load a roof where it falls but where wind and slide pile it, so frame the drifts before the field.
13 min read10 sections10 calculators2026-08-28
Structure
Detailing a Steel Bracing Bay
Sizing the diagonal in a braced bay, then proving the gusset it lands on will not tear out before the rod itself has yielded.
17 min read8 sections10 calculators2026-08-31
Carpentry
Levelling and Scribing Kitchen Units
The set-out left one line on the wall. This is the day eleven carcases have to meet it, and the floor, the wall and the doors all disagree about where it is.
23 min read11 sections11 calculators2026-08-31
Carpentry
Fitting Skirting and Architrave
No corner is square, so the joints carry the job: where to scribe, where to mitre, and how to hold one margin round every door lining in the house.
19 min read12 sections9 calculators2026-08-31
Foundations
Setting Foundation Depth Near Trees on Shrinkable Clay
On shrinkable clay the tree sets the dig, not the load — how species, distance and plasticity index become a trench depth, and what goes on its faces.
22 min read11 sections15 calculators2026-09-22
Carpentry
Framing a Gambrel, Mansard or King Post Roof
Gambrel, mansard and king post frames worked from the break line down: chord lengths, the thrust the change of angle makes, and what it does to the order.
17 min read9 sections12 calculators2026-08-31
Carpentry
Framing a Load-Bearing Wall
A bearing wall read as a load path from the ground up: what the sole plate stands on, and how studs, headers and plates hand weight down.
11 min read9 sections11 calculators2026-08-28
Carpentry
Hanging an Internal Door
A leaf fitted into a lining that has been moving for fifty years: what to scribe, what to plane, where the butts go and how the keep lands first time.
17 min read8 sections8 calculators2026-08-31
Structure
Installing a Steel Beam
A steel beam almost never fails in strength — it fails the ceiling underneath, so deflection limits and bearing movement govern the whole install.
10 min read9 sections9 calculators2026-08-28
Carpentry
Jointing a Laminate Worktop
One 3 m length, a hired jig and two cuts that cannot be taken back: choosing male and female, placing the bolts, and sealing a joint that stays shut.
20 min read10 sections6 calculators2026-08-31
Structure
Bolted and Welded Steel Connections
A load-path field guide to steel joints: every bolt, weld, plate and stiffener a force must cross to leave one member and enter the next.
13 min read11 sections8 calculators2026-08-28
Carpentry
Timber Connections That Carry
Timber members rarely break — their joints do, so this field guide sorts carpentry connections by the way each one actually gives way.
12 min read9 sections7 calculators2026-08-28
Carpentry
Ordering Roof Trusses
A fabricator builds what the enquiry sheet says. On a vaulted extension in the lee of a taller roof, span, heel and the drift case decide it.
19 min read10 sections12 calculators2026-08-31
Foundations
Footings, Piers and Frost Depth
Every footing answers to two independent depths — competent bearing and the frost line — and the deeper of the two governs the dig.
10 min read8 sections8 calculators2026-08-28
Structure
Removing a Chimney Breast and Supporting What Is Left
The demolition is a day. The argument is what still stands above the cut, what it weighs, and whether brackets or a beam are going to be accepted for it.
21 min read12 sections15 calculators2026-09-22
Carpentry
Resurfacing a Deck on Its Existing Frame
The frame is the half you inherit. Whether it takes composite at the spacing it already has is a board question first and a joist question second.
18 min read9 sections9 calculators2026-08-31
Structure
Setting Steel Columns and Baseplates
How a steel column is set true at the top where it buckles and bedded solid at the bottom where it crushes, from anchor layout through final grout.
14 min read7 sections8 calculators2026-08-28
Shoring
Shoring a Deep Excavation: Pile Walls and Soil Nails
A basement box beside a neighbour reduces to two numbers: the overlap a bored pile wall still has at its toe, and the bond length a nail needs behind the wedge.
19 min read10 sections10 calculators2026-08-31
Structure
Sizing a Suspended Slab
Slab depth gets fixed before anyone has a load. Here is the ratio that defends it, and the seating loss that decides whether stressing the floor pays.
17 min read8 sections9 calculators2026-08-31
Steel
Spacing Purlins and Deck Supports
Secondary framing set out so purlin rows, deck spans and sheet end laps land on frame lines the primary steel order fixed weeks ago.
17 min read9 sections10 calculators2026-08-31
Foundations
Stepping Foundations Down a Sloping Site
A metre of fall turns one strip footing into a staircase of separate pours. Where the step height, the lap and the made-up ground come from.
23 min read9 sections13 calculators2026-09-22
Structure
Sizing a Floor That Does Not Bounce
A floor can pass span over 360 and still move underfoot. Span, depth and everyday mass set its frequency, and frequency is what the client feels.
16 min read8 sections9 calculators2026-08-31
Steel
Taking Off a Steel Package for Tender
A frame drawing gives you lengths, not weights, and never gives you area. How to close both columns on the afternoon before the return goes in.
21 min read10 sections8 calculators2026-08-31
Finish carpentry
Trimming Out a Room: Crown, Stock Lengths and Board Feet
Crown runs the whole ceiling line, so corners and stock lengths set the order — and the hardwood shed prices the same room by the board foot instead.
17 min read8 sections9 calculators2026-08-31
Steel
Weighing Steel Sections
An imported angle or a cold-formed C states its geometry and nothing else. Measure it, get kilograms per metre, and defend the tonne on the quote.
16 min read9 sections11 calculators2026-08-31
Structure
Cutting a New Stair or Riser Opening Through an Existing Floor
Before a blade turns: what is inside the slab, what holds the floor up while its middle is gone, and how a two-tonne piece of it leaves the building.
21 min read13 sections12 calculators2026-08-31

Concrete and masonry34 guides

Rendering
EIFS Finish Coat: Coverage, Texture and the Joint You Cannot Hide
EIFS finish is one aggregate deep, so a pail covers what the grade says it covers and any edge that skins mid-elevation stays visible for good.
15 min read8 sections7 calculators2026-08-31
Masonry
Checking an Old Masonry Wall Before You Load It
Capacity in old masonry is net area times an allowable stress, and on a standing building neither term can be read off a drawing.
16 min read9 sections9 calculators2026-09-22
Concrete
Bracing Formwork for the Pressure a Pour Actually Makes
A raker resists what would tip a wall form over, not the concrete's push on the sheathing — until the form loses its opposite face and the two become one load.
17 min read9 sections10 calculators2026-08-31
Masonry
Building a Brick Veneer Wall That Drains
A veneer skin is built from the cavity outwards: the anchor grid, the air space and the vent line are all fixed before the scaffold passes them.
16 min read7 sections11 calculators2026-08-31
Masonry
Building a Free-Standing Garden Wall That Stays Up
A boundary wall is a cantilever held down by nothing but its own weight. Where the piers, the trench width, the DPC and the coping come from.
21 min read10 sections11 calculators2026-08-31
Concrete
Building and Bracing Formwork
Formwork pressure follows the rate you fill at, so the pour plan sizes the ties, walers and bracing long before a panel is cut.
12 min read9 sections9 calculators2026-08-28
Concrete
Checking a Ready-Mix Truck at the Gate
The ticket, a thermometer and a weighed bucket answer the two questions the gate can still settle: is this load too hot, and is it the volume ordered?
17 min read9 sections9 calculators2026-08-31
Concrete
Curing Concrete in Heat and Cold
Curing is a race between hydration and evaporation, and every measure on a concrete pour either slows one clock or speeds the other.
11 min read7 sections8 calculators2026-08-28
Concrete
Designing a Concrete Mix and Reading the Submittal
A mix submittal makes three claims - water-cement ratio, sand grading and stiffness - and the review is proving they agree with each other.
19 min read10 sections9 calculators2026-08-31
Concrete
Detailing Rebar: Laps, Hooks and Cover
A concrete field guide to what actually develops a reinforcing bar on site — bond length, hooks, cover and the details that quietly shorten all three.
12 min read7 sections7 calculators2026-08-28
Reinforcement
Rebar Hooks: The Length That Is Not on the Drawing
A hook is a symbol on the section and a real length of steel in the yard. What the bend and its tail consume, and why bar lists come up short.
16 min read9 sections8 calculators2026-08-31
Masonry
Keeping Water Out of a Stone Veneer Wall
Adhered stone is wet for days after rain and the sheathing only survives if the base and every window head were built as exits rather than as edges.
19 min read9 sections9 calculators2026-08-31
Masonry
Estimating Mortar for Walls That Are Not Standard Brick
Bags per thousand is a coverage rate with the unit size, joint width and bed depth frozen inside it. How to unfreeze it for AAC and dressed stone.
16 min read8 sections9 calculators2026-08-31
Masonry
Filling a Hollow Wall: ICF Cores and Grouted Block Cells
A hollow wall gets ordered twice — forms and units by the face, concrete and grout by the void — and only the first number is on the elevation.
19 min read9 sections12 calculators2026-08-31
Masonry
Cavity Trays Where an Extension Roof Meets the House
The tray belongs in a bed joint under two and a half metres of standing brickwork. How to get it there in bays, without losing the panel above it.
21 min read10 sections11 calculators2026-08-31
Masonry
Installing Manufactured Stone Veneer
Corners are sold by the foot and priced like two of everything else, so an adhered stone package is two takeoffs that have to agree at the arris.
20 min read9 sections10 calculators2026-08-31
Concrete
Jointing Concrete Flatwork
Flatwork concrete cracks whether you plan for it or not, so jointing is the trade of choosing the crack line before the slab does.
14 min read7 sections10 calculators2026-08-28
Concrete
Laying a Beam and Block Ground Floor
Choosing a suspended deck over a slab, reading a load/span table three ways, setting a void that has to breathe, and grouting the infill solid.
21 min read12 sections14 calculators2026-08-31
Wet trades
Screeding Over Underfloor Heating Pipes
Ordering a screed off the cover over the tube crown, gauging a ratio that means something, and the three separate waits that follow the pour.
17 min read9 sections10 calculators2026-08-31
Masonry
Laying Brick and Block
Every masonry wall is one course repeated: get the unit, its bed, its perpend and its bond right, and the rest is multiplication.
12 min read8 sections8 calculators2026-08-28
Concrete
Ordering Concrete for a Column Pour
A column lift is under ten cubic metres and has no tolerance either way: short leaves an unplanned joint, long leaves concrete you have to dispose of.
20 min read9 sections10 calculators2026-08-31
Concrete
Placing and Pumping Concrete
A field guide to moving ready-mixed concrete from truck to formwork with its water-cement ratio, air content and workability still intact.
12 min read10 sections9 calculators2026-08-28
Wet trades
Plastering Over Artex
A textured ceiling takes a skim, an undercoat or a new sheet of board depending on one lab result and one depth gauge reading — not on the primer.
19 min read9 sections10 calculators2026-08-31
Concrete
Pouring a Slab From Bagged Mix
A pallet on the drive, no truck access, and a fixed bag count: the area those bags really cover, and the barrow runs and mixing hours behind it.
17 min read9 sections11 calculators2026-08-31
Concrete
The Master Guide to Pouring a Professional Concrete Slab
A pour told in order, from subgrade compaction the week before to the joints, the cure, and the cracks that appear a month later.
17 min read10 sections10 calculators2026-08-28
Concrete
Preparing a Watertight Construction Joint
The evening before a basement pour: whether the joint face will bond, whether the waterstop is continuous, and whether the mat survives boots.
19 min read9 sections9 calculators2026-08-31
Wet trades
Rendering and Plastering a Wall
A coat-by-coat field guide to render and plaster: reading what the background drinks, and keeping every coat weaker and thinner than the one beneath it.
12 min read8 sections9 calculators2026-08-28
Concrete
Replacing a Ground Floor Slab That Has Heaved
The hardcore under a 1950s floor is still reacting. What proves it, what leaves the house by barrow, and whether the replacement bears on the ground or spans it.
21 min read13 sections14 calculators2026-08-31
Masonry
Replacing a Failed Lintel Over a Window
A stepped crack off a window corner is not proof the lintel has gone. What separates the five causes, and what holds the wall while one is changed.
19 min read9 sections13 calculators2026-08-31
Masonry
Repointing and Checking a Parapet
Pricing a repoint from the scaffold: how much joint is really in a parapet, how deep it gets raked, and whether the wall is too slender to leave standing.
18 min read10 sections10 calculators2026-08-31
Masonry
Repointing a Garden or Boundary Wall
Only a band of a garden wall is usually dead. How to find where it stops, how deep to rake, whether it wants lime, and when to rebuild instead.
21 min read12 sections12 calculators2026-08-31
Concrete
Specifying a Warehouse Floor: Flatness Class and Rack Leg Loads
The slab section of a distribution unit turns on two numbers the letting brief never gives you: how the trucks travel, and what stands on one rack leg.
20 min read11 sections17 calculators2026-08-31
Concrete
Specifying Lower-Carbon Concrete
Cement replacement, leaner sections, or a different frame material - three levers on a concrete frame, and only two are still open the month before a pour.
18 min read9 sections8 calculators2026-08-31
Masonry
Turning a Brick Arch Over an Opening
One number — the rise — settles what family the arch belongs to, how hard it pushes sideways, and the taper on every wedge you cut.
18 min read10 sections7 calculators2026-08-31

Roof and envelope61 guides

Facade
Allowing for Movement in a Glazed Panel
A gap set on a cold morning is already spent by August. Metal temperature, not air temperature, decides what a glazing joint has left to give.
20 min read10 sections9 calculators2026-08-31
Building envelope
Attaching Cladding Through Continuous Insulation
Setting out a clip-and-rail grid over exterior insulation: three grids to reconcile, three fastener families to count, and one wall you cannot re-drill.
17 min read9 sections11 calculators2026-09-22
Insulation
Boarding a Loft Without Crushing the Insulation
Decking straight onto the joists buys a shelf and spends the insulation. The raise height, the leg grid and the eaves gap, worked in that order.
19 min read10 sections10 calculators2026-08-31
Roofing
Building a Green Roof the Structure Can Carry
The saturated dead load and the stormwater credit are the same water counted twice. Settle both before a bag of substrate is ordered.
18 min read10 sections11 calculators2026-08-31
Roofing
Building a Pedestal Paver Terrace
The deck falls, the terrace cannot. That disagreement is measured in millimetres of pedestal, and it is a schedule of heights rather than one height.
17 min read11 sections10 calculators2026-08-31
Cladding
Cladding a Portal Frame: Built-Up or Composite Panel
Twin skin built up on site against factory composite panel, and the spacer bar that quietly caps the U-value whatever thickness of quilt you buy.
20 min read11 sections13 calculators2026-08-31
Insulation
Deciding Whether a Cavity Wall Should Be Filled
The suitability survey takes twenty minutes and cannot be undone: what disqualifies a cavity wall from being filled, and what to do if it already was.
21 min read11 sections15 calculators2026-08-31
Building envelope
Designing Timber Louvers for Shade
A west elevation has no winter to trade against: December sun meets a horizontal screen at a steeper angle than July sun does, and blade spacing follows from that.
17 min read8 sections10 calculators2026-08-31
Facade
Detailing a Building Expansion Joint
A separation joint is one plane through a whole building, and it is priced by the piece. What crosses it, who owns each crossing, and what the corners cost.
17 min read9 sections8 calculators2026-08-31
Roofing
Detailing a Parapet and the Cricket Behind a Curb
A parapet gets weather on three faces and a cricket is the only slope you build by hand — this is what both cost in metal, board and flashing height.
18 min read9 sections10 calculators2026-08-31
Damp
Telling Rising Damp, Penetrating Damp and Condensation Apart
Four mechanisms wet a wall and only one is cured by drilling it. What separates them, measured rather than asserted, before a treatment is bought.
20 min read12 sections15 calculators2026-08-31
Building envelope
Draught-Proofing Doors and Windows
A candle finds the gaps; the merchant needs lengths. Surveying an old house opening by opening, then turning the round into rolls, sweeps, film and tubes.
19 min read10 sections10 calculators2026-08-31
Openings
Draught-Proofing and Secondary Glazing for Sash Windows
Consent says the sashes stay. What brush seals, an overhaul and secondary glazing each buy, what each costs the window, and the U-value each one reaches.
19 min read10 sections14 calculators2026-09-22
Roofing
Dry-Fixing Ridge, Hip and Verge
A cracked ridge, one quote to re-bed it and one to strip it. What the 2014 revision of BS 5534 removed, and what mortar alone can no longer do.
18 min read9 sections9 calculators2026-08-31
Roofing
Fastening a Roof for Wind Uplift
Wind never loads a roof evenly, so the fastening cannot be even either — marking the corner and edge zones, then setting the pattern each one demands.
19 min read10 sections11 calculators2026-08-31
Cladding
Fastening Lap Siding So It Still Moves
A lap siding schedule decides where each board is pinned and where it stays free. Get that backwards and the board splits at the nail, not at the joint.
18 min read10 sections10 calculators2026-08-31
Building envelope
Fitting a Radiant Barrier Under a Metal Roof
Foil lands in the gap between the steel gang and the sheeters, and the roll count, the lap allowance and the condensation risk are all settled before it does.
17 min read9 sections10 calculators2026-08-31
Roofing
Fitting a Roof Window Into a Pitched Roof
A roof window is ordered twice: once for the unit, once for the flashing kit that has to suit the covering it lands in and the pitch it lands on.
18 min read8 sections12 calculators2026-08-31
Cladding
Fixing Timber Cladding on a Ventilated Cavity
Timber keeps moving after you fix it. Batten depth, batten centres, cavity depth and the fixing line, all sized around that one fact.
19 min read10 sections11 calculators2026-08-31
Waterproofing
Balcony Flashing: Where the Deck Meets the Wall
The doorway is the one junction on a building where a wet outdoor floor meets a dry indoor one at the same level. Detail it outward from there.
18 min read10 sections11 calculators2026-09-22
Roofing
Leadwork Around a Chimney
Four separate pieces wrap a stack and none of them seals. Which detail suits your covering, what code of lead to buy, and how far each piece runs.
20 min read10 sections9 calculators2026-08-31
Roofing
Flashing a Roof Curb
Eleven boxes on a roof are eleven perimeters, eleven blank widths and forty-four corners. Here is how all three reach the shop in one order.
16 min read9 sections10 calculators2026-08-31
Roofing
Framing a Skylight Opening
One catalogue code decides the opening, the header, the curb and the saddle above it — worked in that order, from the unit outward.
16 min read8 sections10 calculators2026-08-31
Rainwater
Harvesting Rainwater From a Roof
One storm off a 35 m² roof plane is about 300 litres. A dry fortnight of beds asks for nearly a thousand. Storage is the gap between the two.
20 min read10 sections10 calculators2026-10-05
Facade
Installing a Curtain Wall
The mullion carries and the glass rides: a facade install organised around the load path from glass to frame to bracket to slab edge.
13 min read9 sections9 calculators2026-08-28
Roofing
Installing a Standing Seam Metal Roof
Standing seam panels expand and contract every single day, and every clip, seam and trim detail either allows that movement or fights it.
12 min read10 sections10 calculators2026-08-28
Damp
Injecting a Remedial DPC and Replastering After It
Hole spacing, cream volume per metre, what the drying wait is really for, and why the replaster over an injected course is a salt specification.
20 min read14 sections12 calculators2026-08-31
Cladding
Installing an EIFS Wall System
An EIFS wall fails at its bond lines, not inside its materials, so build the laminate outward and protect every interface.
12 min read9 sections7 calculators2026-08-28
Cladding
Installing Fibre Cement Cladding
Fibre cement will not forgive a flexed sheet, a blunt blade, a crushed nail head or a drifted reveal — a field guide built around those limits.
11 min read9 sections8 calculators2026-08-28
Cladding
Installing Siding and the Drainage Plane
Siding is a screen, not a seal: build the wall outward so every drop that gets behind the cladding has a way back out.
13 min read9 sections10 calculators2026-08-28
Openings
Installing Windows and Exterior Doors
Windows and exterior doors fail at the sill before they fail anywhere else, so build the pan first and work outward from it to the casing.
13 min read10 sections8 calculators2026-08-28
Building envelope
Warm Deck or Cold Deck on a Flat Roof Over a Room
Insulation above the deck or between the joists: on an extension or a dormer the answer is settled by how far the roof can rise.
20 min read12 sections13 calculators2026-08-31
Building envelope
Insulating an Attic
Attic heat loss ranked biggest hole first: air leakage, bare gaps, depth, the hatch, ducts, then the eave perimeter.
12 min read10 sections9 calculators2026-08-28
Building envelope
Insulating a Sloping Ceiling in a Room in the Roof
A 100 mm rafter cannot carry 100 mm of board and a clear air path. How the depth gets split between, under and over, and what it costs.
21 min read12 sections14 calculators2026-09-22
Insulation
Insulating a Suspended Timber Ground Floor
The void under a period floor is a drying machine. Insulate between the joists without switching it off, and the floor gets warm instead of rotten.
21 min read13 sections13 calculators2026-08-31
Building envelope
Insulating a Wall Without Thermal Bridges
Framing is the hole in a wall's insulation: what interrupts the thermal layer on a job site, and what restores it.
11 min read9 sections9 calculators2026-08-28
Roofing
Laying a Clay Barrel Tile Roof
Barrel tile is heavy, brittle and counted piece by piece — and how it reaches the roof is settled by a ladder rule, not by how strong the crew is.
19 min read11 sections12 calculators2026-08-31
Roofing
Low-Slope and Flat Roofing
On a flat roof every failure has an address: find where the water stops, then price what it costs in build-up to move it.
12 min read9 sections10 calculators2026-08-28
Waterproofing
Falls, Tanking and the Gully in a Wet Room Floor
A walk-in shower cut into a floor that already exists: the depth budget under it, the gradient band the codes barely leave open, and the tanking above it.
20 min read14 sections14 calculators2026-09-21
Openings
Laying Out a Doorway That Works
Moving a door means rebuilding a hole: the leaf sets the frame, the frame sets the opening, and the floor either side decides where it can go.
15 min read8 sections9 calculators2026-08-31
Glazing
Laying Out a Storefront
A shopfront opening becomes a lite count, four runs of track and a glass order, and the smallest of four ceilings — not the elevation — sets the division.
17 min read9 sections10 calculators2026-08-31
Glazing
Lifting and Setting Heavy Glass
A panel schedule arrives in millimetres and has to leave in kilograms, unit by unit, before anyone decides what two pairs of hands can take.
16 min read8 sections8 calculators2026-08-31
Roofing
Measuring a Roof From the Ground
Quoting a re-roof off plan dimensions and a pitch read from the driveway, then sizing a ladder that actually reaches the eave.
17 min read8 sections11 calculators2026-08-31
Glazing
Ordering Insulated Glass Units
A blown unit leaves one free variable. The pocket fixes overall thickness, the panes you pick decide the spacer, and the spacer decides the argon.
19 min read10 sections8 calculators2026-08-31
Building envelope
Getting a Large Building Through Its Air Leakage Test
The target divides by envelope area, not floor area, and on a big shed that one distinction is most of the result. Booking it, sealing it, and the day itself.
21 min read10 sections11 calculators2026-09-22
Glazing
Planning a Revolving Door Entrance
A revolving door is four different diameters and a reserved circle, tested against the lobby before the storefront around it is drawn.
16 min read8 sections9 calculators2026-08-31
Roofing
Replacing a Slipped or Broken Slate
One slate down is a tingle and an hour. Six down in a winter is a nail count and a scaffold — how to tell which of the two you are holding.
19 min read8 sections10 calculators2026-08-31
Roofing
Replacing Fascia, Soffit and Bargeboard
Capping over a tired fascia and stripping it back to the rafter feet buy the same frontage and commit you to very different buildings.
19 min read11 sections8 calculators2026-08-31
Roofing
Setting Out a Slate or Cedar Roof
Gauge, margin and headlap fixed with a chalk line on bare rafters, and the course arithmetic that has to close before slate or cedar is ordered.
17 min read8 sections11 calculators2026-08-31
Roofing
Setting Out Roof Battens: Gauge and Headlap
The eaves line, the top line, and a whole number of equal steps between them — how a batten gauge gets settled without ever giving up headlap.
20 min read8 sections12 calculators2026-08-31
Roofing
Shingling a Roof
Shingling judged the way water judges it: every lap, nail and flashing traced from the ridge slot down to the gutter line.
14 min read10 sections8 calculators2026-08-28
Rainwater
Sizing a Rainwater Harvesting Tank
Eighteen days of the smaller of annual yield and annual demand. On a 74 m² roof that is under 2,000 litres, and the 6,000 in the brochure is a fault.
22 min read9 sections13 calculators2026-10-05
Rainwater
Sizing Gutters and Downspouts
A rainwater run carries only what its tightest point allows, so size the trough, the outlet drop and the leader against one storm.
13 min read10 sections8 calculators2026-08-28
Glazing
Spacing Structural Glass Fins and Glazing Bars
A fin count and a bar count both fall out of a spacing somebody else approves — and that one number then fixes the pane, the bite and the lift.
17 min read8 sections11 calculators2026-08-31
Glazing
Specifying Glass Against a Performance Requirement
How to read a glazing submittal: what a published rating is attached to, which report proves it, and where the screening arithmetic stops.
18 min read8 sections9 calculators2026-08-31
Facade
Curtain Wall Condensation: Where the Warm Side Stops
The glass can be bone dry while the mullion beside it runs with water. Condensation finds the coldest room-side surface, and that is nearly always the frame.
20 min read12 sections10 calculators2026-09-22
Building envelope
Stopping Ice Dams at the Eaves
Icicles are a symptom with an address. Read the melt pattern, find the warm air reaching the deck, then clear the eave path.
19 min read9 sections11 calculators2026-08-31
Waterproofing
Tanking a Basement Wall Against Standing Water
Below the table a wall has to hold head, not shed it: set the design water level, work out what the ground delivers, then confine the bentonite.
16 min read8 sections12 calculators2026-09-22
Building envelope
Balancing Roof Ventilation
Roof intake and exhaust form a single pressure loop — the failures all trace back to one side outrunning the other.
11 min read11 sections8 calculators2026-08-28
Facade
Planning How the Facade Gets Cleaned and Maintained
The access method is settled by the roof plan years before a cleaning contractor exists — parapet, deck loads, reach and restraint all freeze together.
18 min read9 sections11 calculators2026-08-31
Facade
Water Testing a Facade on Site
A nozzle proves a sealed joint and nothing else. Which field method the specification actually bought, who has to witness it, and what one fail costs.
22 min read11 sections10 calculators2026-08-31

Interiors and finishes36 guides

Interiors
Building a Curved Drywall Wall
A radius partition set out, framed, kerfed and beaded by one piece of arithmetic: how far a chord sags away from the arc it spans.
19 min read8 sections9 calculators2026-08-31
Conversions
Checking Whether a Loft Can Be Converted
Head height, roof type and joist depth, measured off the timber rather than the plaster, and what each one leaves: a room, a dormer, or nothing.
21 min read11 sections12 calculators2026-08-31
Conversions
Converting an Integral Garage Into a Room
Building up from a slab poured to drain: the floor stack, the infill under the old lintel, and holding the damp line unbroken across the threshold.
21 min read11 sections16 calculators2026-09-22
Renovation
Cutting an Opening in a Masonry Wall
Widening an opening is two load questions in order: what each prop holds while the wall is open, and what the angle under the brickwork holds afterwards.
18 min read9 sections9 calculators2026-08-31
Interiors
Detailing a Large Ceiling
A big ceiling is decided at its edges and its breaks: where the run is interrupted, and how much perimeter trim is ordered before boarding starts.
15 min read8 sections8 calculators2026-08-31
Interiors
Dry-Lining a Solid Wall
Dabs or a furring grid on a solid masonry wall: what the substrate decides, and why each route hands the estimator a different thing to count.
18 min read9 sections11 calculators2026-08-31
Coatings
Estimating Coatings for Block Walls and Timber Fences
A printed spread rate is measured on a smooth panel; open block and rough-sawn timber break that assumption by factors, not by percentages.
18 min read8 sections8 calculators2026-08-31
Interiors
Taping and Finishing to a Level
Levels 0 through 5 are a ladder of coats and scrutiny: what each rung costs, what light exposes, and where a specification should stop.
10 min read9 sections8 calculators2026-08-28
Interiors
Fitting Coving and Cornice
Coving is bedded on adhesive and its joints are filled rather than fitted, which changes the cut in the mitre box, the order round the room and the buy.
20 min read9 sections9 calculators2026-08-31
Interiors
Framing a Cold-Formed Steel Partition
A tall steel partition decided the way it fails: section against the movement limit first, then the fastener counts that fall out of it.
17 min read8 sections9 calculators2026-08-31
Interiors
Hanging a Suspended Ceiling
A suspended ceiling is a grid borrowed from structure that never expected it — work upward from tile face to hanger wire to deck.
12 min read7 sections7 calculators2026-08-28
Interiors
Hanging Drywall
Hanging drywall as a chain of decisions — board direction, joint placement, fastener depth — and what each one costs the finisher later.
13 min read9 sections10 calculators2026-08-28
Finishes
Hanging Wallpaper: Setting Out and Pattern Repeat
Where the first drop lands decides the room: motif centred on the breast, cut length set by the repeat, and the break parked behind the door.
19 min read9 sections6 calculators2026-10-05
Interiors
Installing a Raised Access Floor
A raised access floor is governed by the single loaded caster that crosses it, not by the kilonewtons per square metre on the schedule.
12 min read10 sections10 calculators2026-08-28
Flooring
Floating Floor Installation
A floating floor is one raft that changes size all year; every gap, break and transition you cut exists to let it move.
12 min read10 sections7 calculators2026-08-28
Flooring
Laying a Herringbone Floor and Trimming It Out
Herringbone spends its material at the walls, not in the middle, and the perimeter it leaves behind still has to be closed and covered.
18 min read11 sections8 calculators2026-08-31
Finishes
Laying a Resinous Floor
Resin floors fail at the slab, not the topcoat — read moisture, profile and contamination before any resin is opened.
13 min read8 sections9 calculators2026-08-28
Flooring
Laying a Parquet Floor
Blocks are counted by the repeat rather than the piece, and the void at the wall is sized from the moisture the room will settle at, not from habit.
16 min read9 sections7 calculators2026-08-31
Flooring
Laying Carpet and Carpet Tile
Broadloom arrives at a fixed width, so seam placement — not room area — drives every carpet and carpet-tile decision on site.
11 min read10 sections8 calculators2026-08-28
Tiling
Setting Floor Tile
Floor tile is set out before it is set: the first two lines you strike decide every cut, joint and threshold in the room.
11 min read8 sections9 calculators2026-08-28
Finishes
Marking Out Lines and Sports Courts
A court is a geometry problem that ends in a spray gun: how to set out, prove and record the lines before any paint is mixed.
11 min read9 sections6 calculators2026-08-28
Finishes
Painting Interior Walls
On interior work the substrate sets the numbers: porosity, adhesion and the old colour decide coverage, primer class and coat count.
12 min read9 sections6 calculators2026-08-28
Finishes
Painting Woodwork and Trim
Why a white gloss goes ivory behind the door, what a live knot does to a waterborne film, and how a metre of moulding becomes a square metre of paint.
21 min read11 sections10 calculators2026-08-31
Renovation
Planning a Kitchen Remodel: What Comes Out and What Goes Back
Strip-out week is two forms filled from one tape: an area for the fabricator to quote against, and a container sized by what the room weighs.
20 min read8 sections9 calculators2026-08-31
Flooring
Preparing a Subfloor for LVT and Vinyl
Vinyl is thin enough to report everything under it, so the survey — not the spec — decides whether you buy a moisture test, a suppressant, a primer or a pour.
18 min read10 sections10 calculators2026-08-31
Interiors
Overboarding or Taking Down a Lath and Plaster Ceiling
Two answers to a bowing Victorian ceiling — board over it or take it out — and the screw length, dust and container size that decide which.
21 min read12 sections15 calculators2026-08-31
Renovation
Re-Treading a Staircase Over Existing Stringers
A tread cap adds thickness to every step and to neither floor, so the bottom riser grows and the top one shrinks by exactly the cap thickness.
20 min read9 sections10 calculators2026-08-31
Flooring
Sanding and Finishing a Timber Floor
The wear layer is finite and the machine is hired by the day, so the grit sequence, the oil-or-lacquer call and the coat count are all settled first.
20 min read11 sections7 calculators2026-08-31
Kitchens
Setting Out a Kitchen: Clearances, Runs and Services
Fixed modules, a room that is wider at one end, and services that have to be right before the plaster goes on. Setting out a kitchen from one datum.
22 min read12 sections14 calculators2026-08-31
Finishes
Setting Out Terrazzo Divider Strips
Panelling a lobby before the pour is booked: strip lines taken off the column grid and the slab joints, then counted into brass and trim.
18 min read9 sections6 calculators2026-08-31
Tiling
Setting Out Wall Tiles in a Bathroom
A bathroom wall offers more datums than a grid of courses can honour — rim, ceiling, niche, window — and setting out is choosing which one gets the full course.
23 min read13 sections14 calculators2026-08-31
Interiors
Drywall Finish Levels and What Each One Costs in Compound
Below Level 5 compound is bought along the seams; at Level 5 it is bought over the whole wall. That change of unit, not extra care, is what doubles the order.
15 min read9 sections8 calculators2026-08-31
Interiors
Taking Off Board for Shafts, Soffits and One-Sided Walls
A riser priced as a two-sided partition buys twice the board, misses the liner completely, and never checks whether the stud height works.
17 min read7 sections9 calculators2026-08-31
Tiling
Tiling a Commercial Kitchen Floor
Quarry tile priced the way a kitchen fails it: falls to the gullies, ten-millimetre joints in chemical-resistant grout, a trim on every edge that stops.
18 min read7 sections12 calculators2026-09-22
Fit-out
Taking On a Cat A Shell and Scoping the Cat B
A Cat A floor arrives finished and almost none of it survives your layout. The Cat B scope is the delta, and it has to be measured twice.
21 min read10 sections13 calculators2026-08-31
Fit-out
Stripping Out a Fit-Out at Lease End
A schedule of dilapidations lands eleven weeks before expiry. Which items the consents oblige you to remove, and what the strip-out actually weighs.
20 min read12 sections13 calculators2026-08-31

Site and groundwork74 guides

Below grade
Backfilling Against Waterproofing
Filling is the one operation that can destroy a membrane without leaving a mark: board it, place it in lifts, and prove the drain takes what arrives.
17 min read8 sections11 calculators2026-09-22
Earthworks
Balancing Cut and Fill on a Wet Site
A site balances on the drawing long before it balances in the dirt: shrinkage and a formation wet of optimum each take their share of the cut first.
17 min read8 sections9 calculators2026-09-02
Warehousing
Building the Floor of a Cold Store So It Does Not Heave
The frost front under a freezer never retreats, so the insulation, the vapour barrier and the sub-floor heating grid all have to be right in one pour.
21 min read11 sections18 calculators2026-08-31
Paving
Getting a Dropped Kerb Built and Paved to Meet It
Forty square metres of new block paving with no lawful way onto it: proving the frontage is deep enough, who may cut the kerb, and meeting the channel.
19 min read9 sections11 calculators2026-08-31
Hardscape
Building a Gabion Wall
A gabion is a container, not a structure. The trade sits in mesh aperture, in the fill's placed bulk density, and in what the bottom course beds on.
19 min read11 sections12 calculators2026-09-21
Hardscape
Building a Retaining Wall
A hardscape field guide organised around the two ways retaining walls fail: rotating about the toe, and sliding forward on the base.
16 min read15 sections11 calculators2026-08-28
Flood protection
Building a Sandbag Flood Barrier
A rising river and one working day: setting the line and the height, turning that into a bag count, and turning the bag count into loads of sand.
18 min read9 sections8 calculators2026-08-31
Landscaping
A Seat Wall: Height, Depth and the Concrete Under It
Sitting height is a sum with the cap inside it, seat depth is bought in cubic metres, and the footing is sized by frost because nothing above it weighs enough.
20 min read10 sections13 calculators2026-08-31
Hardscape
Building Steps Into a Garden Slope
Dividing an awkward bank into equal risers, matching the going to the ground you actually have, and laying every tread to a fall so it drains instead of icing.
20 min read11 sections14 calculators2026-09-22
Geotechnical
Building on Soft Ground: Improve It or Pile Through It
Low blow counts under a pad force one choice before the foundation is priced: stiffen the ground you have, or carry the load past it.
19 min read7 sections10 calculators2026-09-22
Drainage
Building an Extension Over or Near a Drain
A manhole inside the footprint is a consent question before it is a building one: whose pipe it is, whether it moves, and who signs it off.
20 min read10 sections13 calculators2026-08-31
Stormwater
Permeable Paving and Storage Below It
A permeable pavement is a tank built out of gaps, and every layer from joint aperture to subgrade earns its keep by void ratio.
14 min read9 sections8 calculators2026-08-28
Sitework
Traffic Calming and Signage on a Private Road
Pricing an estate road's calming works: humps sized off their profile, a hole under every sign, and the glass that makes the lines exist at night.
19 min read7 sections9 calculators2026-08-31
Strip-out
Checking a Pre-2000 House Before You Strip It Out
Which materials in a 1970s house go to a laboratory first, which are non-licensed work, and what the answers do to the container schedule.
22 min read14 sections12 calculators2026-08-31
Heavy civil
Retaining Wall Sliding: The Check That Fails Before Overturning
Widening a base lifts the overturning factor much faster than the sliding one, and the passive resistance closing that gap is one service trench from gone.
22 min read12 sections11 calculators2026-08-31
Sitework
Clearing and Grubbing a Wooded Lot
A treed lot bills twice: once for the brush and stumps it makes, and again at the scale house, where soil on a root ball changes the rate you pay.
17 min read11 sections13 calculators2026-09-22
Sitework
Erosion and Sediment Control
Every erosion and sediment control on a jobsite does one of two things: it slows water down, or it catches the soil that water is already carrying.
14 min read10 sections9 calculators2026-08-28
Sitework
Designing a Site Entrance Trucks Can Use
Gate, keypad and apron sized off two questions: can the delivery swing in off the street, and where does the queue behind it stand while it waits?
21 min read10 sections10 calculators2026-08-31
Geotechnical
Dewatering an Excavation
Below the water table you either pump the ground down and pay for it outside your boundary, or hold the hole with head and pay for it in wall.
20 min read9 sections9 calculators2026-09-22
Excavation
Digging Without Hitting a Buried Service
Most strikes happen on holes too small to feel like excavation — so here is the records, scan, trial hole and machine-margin sequence in full.
20 min read10 sections10 calculators2026-09-22
Stormwater
Draining a New Driveway So It Stays Permitted Development
A front drive whose water reaches the road is not permitted development: the porous surface, the receiving border, the application, and proving which you built.
20 min read9 sections11 calculators2026-08-31
Landscaping
Draining a Waterlogged Lawn
Standing water is either a pan you can break or a table you must drain to. Separate the two, then set laterals, fall and an outfall you may legally use.
21 min read11 sections13 calculators2026-09-22
Below grade
Draining a Wet Basement
Wet basements are a pressure problem: read the head, relieve it at the slab and footing, and pump only what the relief path actually delivers.
11 min read8 sections10 calculators2026-08-28
Irrigation
Drip Irrigating Planting Beds
A drip grid cannot be watched, so its schedule is computed: emitter discharge over the grid area gives depth per hour, and the mulch goes over the tube.
17 min read8 sections11 calculators2026-08-31
Site setup
Fencing a Site Perimeter
Panel counts taken off a walked line, gates sized by the wagon that uses them, and the moment balance that decides whether feet alone hold a run.
18 min read11 sections9 calculators2026-08-31
Landscaping
Fencing a Sloping Garden: Stepped or Raked
Stepped panels or a raked board fence, decided by the infill — then post lengths, setting out in plan, and the board that closes the wedge.
20 min read10 sections11 calculators2026-08-31
Rural fencing
Fencing for Stock, Poultry and Dogs
Three enclosures on one docket: strand-metres for the paddock, hardware cloth counted by the course, and a buried loop that is not a fence at all.
18 min read8 sections8 calculators2026-08-31
Landscaping
Filling a Raised Bed With Soil and Compost
One box, one delivery: the finished volume, the settlement allowance that keeps it up at the rim, and the share of the load that should be compost.
17 min read9 sections10 calculators2026-08-31
Below grade
Fitting a Radon Sump and Fan
A result above the action level is a pressure problem: where the suction point goes, how many the floor needs, and which fan holds the field.
20 min read12 sections10 calculators2026-08-31
Irrigation
Fixing Dry Spots in a Lawn
The same patch browns every August. Cans on a grid separate a run-time fault from a spacing, pressure or soil fault before anything is bought.
20 min read9 sections10 calculators2026-08-31
Site setup
Getting Plant and Deliveries Onto Soft Ground
Ramp geometry off the deck, fabric and stone across the wet, and the stabiliser leg that goes through while a delivery is being taken.
19 min read11 sections11 calculators2026-08-31
Earthworks
Getting Excavated Spoil Off a Small Site
A rear extension makes four kinds of spoil, not one heap — and each carries its own density, its own vehicle and its own answer on contamination.
20 min read11 sections14 calculators2026-08-31
Sitework
Grading a Site for Drainage
Trace every drop from the divide above the pad to the permitted outlet, and size the grade at each transition it crosses.
12 min read8 sections11 calculators2026-08-28
Sitework
Heated Driveways: Cable Spacing, Load and Running Cost
Snow melt cable is sized in watts per square metre, but it is the rating of the incoming supply that decides whether the driveway can be heated at all.
19 min read10 sections14 calculators2026-08-31
Below grade
Laying a Radon or Ground Gas Membrane Under a Slab
Ground gas protection is one-shot work: the venting blanket, the welded laps, the top hats and the perimeter tuck are all buried the day the slab goes down.
18 min read10 sections11 calculators2026-08-31
Landscaping
Preparing the Ground for Artificial Grass
Dig depth worked backwards from the damp course, the sub-base argument settled by the subgrade, and the pile all running one way before anything is glued.
20 min read10 sections14 calculators2026-09-21
Sitework
Laying a Gravel Driveway
Angular stone locks and rounded stone rolls — how to build a gravel drive layer by layer so it stays where you put it.
11 min read8 sections10 calculators2026-08-28
Hardscape
Laying a Patio Against the House Without Bridging the DPC
Two courses of brick between the ground and the damp course, and a back door that wants to be flush: the three ways that gets resolved.
19 min read11 sections13 calculators2026-09-21
Paving
Open-Graded Bedding: The Layer That Has to Stay Open
Fifty millimetres of single-sized stone that must never be compacted, walked on, or topped up with anything a quarry has not washed.
16 min read9 sections8 calculators2026-08-31
Paving
Laying a Resin Bound Surface Over an Existing Drive
Resin bound is 18 mm of wearing course with no structural value. What the core says about the old drive decides the job, not the sample board.
20 min read10 sections12 calculators2026-09-21
Sitework
Laying Out a Car Park
The vehicle you cannot turn away sets aisle width, stall angle and stall count on a site lot - lay it out from the swept path outward.
12 min read10 sections9 calculators2026-08-28
Warehousing
Laying Out Pallet Racking and Aisles to Suit the Trucks
Stack aisles taken off the truck's own type sheet, bay pitch built outward from the pallet, and the survey that decides whether the top level exists.
19 min read11 sections10 calculators2026-08-31
Hardscape
Laying a Paver Patio or Drive
A hardscape field guide organised around the load path: the compacted base is the real pavement, and the pavers are only its wearing course.
13 min read8 sections9 calculators2026-08-28
Hardscape
Laying Outdoor Porcelain on a Full Mortar Bed
Vitrified porcelain has no suction, so nothing sticks to it by accident: bed depth, sand grade, slurry primer and joint width all become specifications.
18 min read11 sections12 calculators2026-08-31
Earthworks
Measuring a Plot: Acres, Hectares and Square Feet
The deed says acres, the mapping says hectares and the quote says square feet. Reconciling all three on one parcel, and knowing which one to sign against.
18 min read9 sections10 calculators2026-09-22
Stormwater
Meeting a Stormwater Runoff Condition on a Tight Site
A condition caps discharge and the plan has no room for a basin. What a vegetated roof is credited with, what stone holds, and which one empties in time.
19 min read9 sections11 calculators2026-08-31
Landscaping
Ordering Fabric, Mulch and Gravel for a Planting Bed
A bed is measured once and leaves the yard three ways: whole rolls of barrier, cubic yards of bark, and a stone tonnage the tipper can legally carry.
16 min read8 sections13 calculators2026-09-22
Paving
Overlaying an Asphalt Surface
An overlay adds thickness to a surface that already has levels in it. What the old mat allows, what the ironwork costs, and how cores settle it.
19 min read10 sections10 calculators2026-08-31
Demolition
Planning Demolition and Debris Removal
Demolition estimates are drawn in solid volume but paid in loose volume, and the swell factor between them decides how many lorries you book.
11 min read10 sections8 calculators2026-08-28
Landscaping
Planning Irrigation and New Turf
Matched precipitation rate governs every irrigation zone: group heads by output before layout, then set turf and run times to the rate you measured.
11 min read9 sections11 calculators2026-08-28
Sitework
Industrial Asphalt Pavement & Sitework Prep
A layer-by-layer read of an industrial asphalt section, from subgrade bearing up to joint density, with traffic loading setting every depth.
15 min read10 sections10 calculators2026-08-28
Grounds maintenance
Quoting a Mowing and Mulch Round
The same 2,900 m² of grass is 21 minutes of deck time or 57, depending on one gate. Turning a walked property into crew minutes and a spring top-up.
19 min read11 sections9 calculators2026-08-31
Geotechnical
Reading a Soil Report
A lab sheet gives specific gravity and dry density; a wall check wants moist and buoyant unit weight. The conversion between them, and where it goes wrong.
20 min read12 sections11 calculators2026-09-22
Paving
Diagnosing and Relaying Sunken Block Paving
A dip where the car parks has four plausible causes at four different depths. Telling them apart in a morning, before anything is lifted.
19 min read10 sections11 calculators2026-08-31
Sitework
Excavating and Containing Japanese Knotweed on a Site
A knotweed dig is measured from inspection pits, not off a drawing — and land, not price, decides between a lined cell, a cap and a licensed gate.
20 min read9 sections12 calculators2026-08-31
Pavement maintenance
Resealing and Restriping Asphalt
A repaint is an alteration, not housekeeping. Why 244 stalls across two lots owe nine accessible spaces, and what that does to a seal-and-stripe.
20 min read10 sections11 calculators2026-08-31
Demolition
Running a Debris Chute Down a Building
Bracket a chute at the spacing its maker publishes, then treat whatever leaves the top opening as arriving at the bottom carrying the whole drop.
16 min read10 sections10 calculators2026-08-31
Below grade
Sealing and Conditioning a Crawlspace
Encapsulating a crawlspace is dew-point work: every liner, foam board and dehumidifier decision either moves a condensing surface out of trouble or leaves it there.
11 min read10 sections10 calculators2026-08-28
Landscaping
Setting a Fence That Stays Up
A fence is a sail before it is a boundary — here is how wind load decides post depth, bay spacing and infill on a landscaping job.
10 min read6 sections8 calculators2026-08-28
Site security
Setting Bollards and Concrete Barriers
Precast barrier is counted by the segment, a bollard is poured by the hole: how to price and book both before the trucks are ordered.
16 min read8 sections9 calculators2026-08-31
Earthworks
Setting Out a Building With Profiles and a Tape
Pegs, string and one tape the day before the digger: finding the building line, proving the base by its diagonals, and landing the curve where the drawing put it.
19 min read8 sections11 calculators2026-08-31
Site setup
Setting Up a Site Compound
A site compound is the fenced base of a building job: welfare cabins, stores, laydown and parking. Its power supply, and what its laydown really holds.
16 min read10 sections12 calculators2026-08-31
Waste management
Setting Up the Waste Compound on a Site
The wagon lays out a waste compound, not the skips — and the caustic washout that no container will take needs its own lined corner of it.
15 min read10 sections11 calculators2026-08-31
Stormwater
Sizing a Swale or Roadside Ditch
Peak flow is handed to you by the catchment and the storm. The channel is the only part you get to design, and it has to pass two checks, not one.
19 min read8 sections9 calculators2026-08-31
Stormwater
Sizing a Soakaway From a Percolation Test
Three timed water drops in a trial pit give one infiltration rate. Storage volume, crate count and the half-drain check all fall out of it.
21 min read11 sections14 calculators2026-09-22
Landscaping
Sizing a Water Feature's Pump
A fountain pump gets sized twice — once for turnover, once for the plume — and the mains top-up brings a relief discharge the courtyard has to swallow.
19 min read10 sections16 calculators2026-08-31
Geotechnical
Sizing Driven Piles in Soft Clay
Fill placed to preload a soft clay hangs on every pile driven through it. Downdrag is a load to add, never a resistance to count.
18 min read8 sections9 calculators2026-09-22
Geotechnical
Underpinning a Wall in Sequenced Pits
A hit-and-miss underpin is bought by the visit, not the cubic metre — and the neighbour's basement is about to remove the soil holding the wall back.
17 min read9 sections10 calculators2026-09-22
Demolition
What the Steel Off a Strip-Out Is Worth
A strip-out's steel is either revenue or skip volume. Tonnage, grade and the loose cube decide which, and all three are settled before a price is quoted.
19 min read8 sections9 calculators2026-08-31
Site setup
Working to a Data Sheet in the Other Unit System
The tub is metric, the gauges in the van are not, and the sheet holds three kinds of number — only one of which survives being multiplied by a factor.
19 min read9 sections14 calculators2026-08-31
Demolition
Working in an Occupied Building Without Closing It
A refit above a live entrance runs two containments: dust held in a sealed enclosure at negative pressure, and the public moving past under a protected route.
17 min read10 sections9 calculators2026-08-31
Excavation
Trench Safety and Support
Soil classification is the design input for every trench — it sets the batter, the bench and the shield, and it changes mid-dig more often than crews expect.
14 min read11 sections8 calculators2026-08-28
Warehousing
Setting Out a Loading Dock and Truck Apron
Sill height, leveller stroke, door centres and court depth are one dimension chain, and the finished floor level settles all four before any equipment is ordered.
21 min read10 sections12 calculators2026-08-31
Site setup
Sizing the Welfare Compound for the Workforce
Sanitary units, basins, canteen seats and drying-room kilowatts taken off a peak headcount, plus the tanker interval that really sizes the tank.
20 min read12 sections14 calculators2026-08-31

Building services71 guides

Heating
Balancing a Hydronic System
Water goes where resistance is lowest, so every emitter that is warm enough is stealing from one that is not, and balancing is how you stop it.
19 min read12 sections9 calculators2026-09-22
HVAC
Balanced Ventilation and Heat Recovery
Air in equals air out: how to set, size, duct, prove and defend the ventilation balance on real HVAC jobs.
12 min read9 sections10 calculators2026-08-28
Water supply
Boosting a Weak Incoming Water Supply
A shower that dies when a tap opens is a flow problem, not a pressure one, and the service pipe has to be measured before anyone prices a pump.
20 min read9 sections10 calculators2026-08-31
HVAC
Building and Commissioning a Cleanroom
An ISO-class fit-out priced and proved the way it is tested: air changes, filter face velocity, a pressure cascade that holds, and an entry that works.
20 min read9 sections10 calculators2026-08-31
HVAC
Residential Thermal Load Calculation & Design Manual
A component-by-component anatomy of the residential heating and cooling load, and what happens when it meets the equipment catalogue.
14 min read12 sections11 calculators2026-08-28
Heating
Choosing a Cylinder a Heat Pump Can Actually Heat
On a changeover the cylinder is judged on the square metres of its coil, not its litres — the same coil sees roughly a quarter of the driving temperature.
21 min read10 sections11 calculators2026-08-31
Plumbing
Matching a Shower to the Water Supply You Have
A shower valve carries a minimum working pressure on its box, and a loft-fed house rarely has it — so four measurements decide the product, not the showroom.
22 min read13 sections13 calculators2026-08-31
Heating
Cleaning a Heating System Before a New Boiler
A modern appliance guarantee is a water-quality condition in disguise. Which clean the system actually needs, and the dose its real litres decide.
24 min read13 sections9 calculators2026-08-31
Electrical
Connecting a Standby Generator
Connecting a set is a switching problem first: one source at a time, a neutral decided on purpose, and a carried-load list that stays honest.
17 min read11 sections9 calculators2026-08-30
Renewables
Getting Solar and a Battery Connected: Notification and Export Limits
The network assesses what the inverter can push out, not what is on the roof — so the connection route has to be settled before the order goes in.
18 min read11 sections11 calculators2026-08-31
Water supply
Controlling Legionella Risk in a Water System
The assessment is not a certificate. It is a list of dated actions with owners — a tail cut out, a cistern turned over, a flush timed in seconds.
21 min read11 sections10 calculators2026-08-31
HVAC
Cooling an Upstairs That Overheats
Top-floor bedrooms that run hot every July: what to log first, then the order to change roof gain, air movement and moisture before buying capacity.
18 min read8 sections13 calculators2026-08-31
Plumbing
Finding What Is Driving a High Water Bill
A bill twice the usual size is a leak, a tariff block or an estimated read. Telling which takes an hour at the meter and a dye tablet upstairs.
21 min read8 sections10 calculators2026-08-31
HVAC
Ducting a Bathroom Extractor Fan So It Does Not Drip
Water at the grille is a duct fault, not a fan fault: the fall, the bore, the lagging and the gap under the door each decide it.
19 min read13 sections13 calculators2026-08-31
Electrical
Earthing and Bonding a Service
Earthing judged the only way it can be — by the ohms you measure, and by which bonds still conduct when a meter is put across them.
18 min read12 sections8 calculators2026-08-30
Heating
Adding Radiators to an Existing Heating System
An extension off the existing boiler is four separate capacity questions, and the appliance is only the first and usually the least interesting of them.
20 min read13 sections12 calculators2026-08-31
Pools
Hot Tub Volume, and Why Every Dose Depends On It
A spa's cylinder estimate can run to nearly twice its real water content, and every instruction on every bottle is arithmetic done against that number.
18 min read10 sections13 calculators2026-08-31
Electrical
Fitting a Consumer Unit
A board changeover read as a survey job: what the old unit reveals, what the new one must carry, and what gets proved before the main switch closes.
18 min read12 sections9 calculators2026-08-30
Heating
Heating a Room With Electric Baseboard
Electric baseboard turns a room's heat load into a length of free wall, and under a basement window that wall runs out before the wattage does.
19 min read11 sections13 calculators2026-08-31
HVAC
Heating a High-Bay Warehouse
Sizing heat for a tall shed whose doors cycle all day: where the setpoint applies, why the stack effect beats the fabric, and radiant against warm air.
21 min read11 sections11 calculators2026-09-22
HVAC
Heat Pumps and the Line Set
A heat pump performs at the capacity its refrigerant path allows, not the capacity stamped on the outdoor unit's nameplate.
11 min read8 sections7 calculators2026-08-28
HVAC
Installing a Heat Recovery Ventilator
An HRV is judged on measured flows at the terminals, and almost all of that result was decided in the ceiling void weeks earlier.
19 min read13 sections9 calculators2026-08-30
HVAC
Installing a Mini-Split
A mini-split is two boxes and a set of tolerances: where each box sits decides capacity, noise, drainage and every joint in between.
18 min read13 sections10 calculators2026-08-30
Electrical containment
Supporting Cable Tray: Load, Spans and the Room It Feeds
Tray is bought by width and loaded by whoever pulls cable into it. The weight accumulates unseen, the hangers are countable, and the room at the end gets hot.
14 min read9 sections9 calculators2026-08-31
Electrical
Installing an EV Charge Point
A charge point sized from the supply backwards: what the service already carries, whether demand limiting beats an upgrade, and which device sees DC.
16 min read11 sections10 calculators2026-08-30
Heating
Fitting a Wood Burner into an Existing Fireplace Opening
The stove is bought and the opening measured. What decides the job now is the hearth under it, the timber near the flue, and the air the room can spare.
20 min read7 sections11 calculators2026-09-22
Heating
Installing a Freestanding Wood Stove and a New Flue
A stove is only as good as the opening framed around its flue, the air the house is willing to spare it, and the fuel stacked a year ahead.
17 min read8 sections10 calculators2026-08-31
Electrical
Installing Cable Tray and Containment
Cable tray comes down to two numbers — how full the section is and how far apart it is held — and every field decision trades one against the other.
11 min read9 sections10 calculators2026-08-28
Electrical
Installing Low-Voltage Landscape Lighting
Sizing a low-voltage transformer to the fixture load it will really carry, then proving the far end of the cable still has volts left to light.
15 min read7 sections7 calculators2026-08-31
Heating
Installing Radiant Floor Heating
A radiant floor gives up only what its surface temperature limit allows, and spacing, water temperature and finishes all follow from that cap.
13 min read10 sections10 calculators2026-08-28
HVAC
Replacing Windows Without Losing the Ventilation
The slot is machined into the frame head before the corners are welded, so which sashes carry a vent is settled on the order and audited room by room.
19 min read11 sections8 calculators2026-08-31
Electrical
Working Out Whether Electrical Work Has to Be Notified
Notification turns on class, location and postcode rather than on size — and on the two moments a small job quietly becomes a notifiable one.
19 min read10 sections7 calculators2026-08-31
Plumbing
Lagging Pipework
Insulation on a pipe is asked to hold heat in, keep a static line above freezing and stop a cold main sweating, and the three want different builds.
16 min read11 sections9 calculators2026-08-30
HVAC
Laying Out Ductwork
The blower table sets a fixed static pressure allowance, and every fitting, filter and flex bend draws on it until the run stops balancing.
12 min read9 sections13 calculators2026-09-22
Electrical
Laying Out Outlets and Alarms in a Room
First fix settled before the board goes on: what the wall rule forces, how deep to hang a box, and where alarms are allowed to land.
20 min read10 sections10 calculators2026-08-31
Electrical
Lighting a Workspace
Lighting design runs from the task backwards: the illuminance a job needs, the depreciation it must survive, and only then a fixture count.
17 min read12 sections10 calculators2026-09-22
Plumbing
Putting a Toilet Where There Is No Soil Stack
The stack is on the far wall and the floor gives you ninety millimetres. Choosing between a gravity branch and a pump starts with that one number.
19 min read13 sections13 calculators2026-08-31
Renewables
Planning a Rooftop Solar Array
A rooftop array is sized by the calendar, not the roof: match monthly production against monthly load and design for the months that fall short.
9 min read7 sections8 calculators2026-08-28
Plumbing
Plumbing a Bathroom
A bathroom is decided in the floor void and the stud cavity, months before anyone sees a tap, and depth is the currency every decision spends.
19 min read12 sections8 calculators2026-09-22
Electrical
Running Power to a Detached Garage
A garage feeder is decided by distance, not by load: terminal temperature, a shared volt budget, and whether a fault can still get home.
18 min read8 sections13 calculators2026-09-22
Medical gas
Purging Medical Gas Pipework: Volume, Rate and Verification
Purge volume is bore volume times a multiple. Whether the line is clear is settled by an analyser at the terminal, never by a stopwatch.
19 min read9 sections7 calculators2026-08-31
Electrical
Putting Charge Points Into a Shared Car Park
How many bays an existing supply carries before anyone quotes a reinforcement: spare capacity inside the charging window, over the floor you guarantee.
20 min read12 sections12 calculators2026-08-31
Electrical
Reading an Electrical Condition Report and Pricing the Remedials
An unsatisfactory report is a verdict on its codes. Which observations start a statutory clock, which are advisory, and how to price only the first kind.
22 min read12 sections11 calculators2026-08-31
Water supply
Recirculating Domestic Hot Water
The wait at the furthest tap is a pipe volume divided by a flow rate, and every method of shortening it costs heat around the clock.
16 min read11 sections8 calculators2026-08-30
Water supply
Replacing the Water Service Pipe
Lead or tired 15 mm iron out and blue MDPE in: route survey, cover depth, the sealed building entry, disinfection, and the connection somebody else makes.
19 min read9 sections11 calculators2026-08-31
Plumbing
Running the Discharge Pipe From an Unvented Cylinder
The discharge is two pipes with two different rules and a safety device between them, and the bend count on the second one is what sizes it.
20 min read10 sections8 calculators2026-09-22
Plumbing
Running Drain, Waste and Vent
Every DWV rule on a plumbing job exists to protect one of two things: continuous fall to the sewer, or free air behind the flow.
10 min read7 sections7 calculators2026-08-28
Hazardous area
Seal-Off Fittings: Stopping a Flame Path Through Conduit
A seal-off plugs a flame front, not water. Where the code fixes it, why a fill limit picks the fitting, and how the compound actually gets poured.
20 min read11 sections8 calculators2026-08-31
HVAC
Setting a Rooftop Unit
Landing a packaged unit on a curb above an occupied floor: corner loads, spring deflection, and the route a service crew wears into the membrane.
17 min read9 sections9 calculators2026-08-31
HVAC
Setting Up an Air Handler for Winter
Winter commissioning at the unit: what the mixing box will really deliver at design outdoor temperature, and how much steam the humidity setpoint costs.
18 min read11 sections9 calculators2026-08-31
Water supply
Private Well Supply and Pressure Tanks
How drawdown volume and pump cycle rate govern every sizing, setting and commissioning decision on a private well water supply.
13 min read7 sections7 calculators2026-08-28
Pools
Pool Circulation and Water Balance
Turnover time sets pump duty, filter area, pipe size, chemical demand and running cost — size it once, honestly, and the rest of the plantroom follows.
13 min read11 sections14 calculators2026-08-28
Renewables
Siting a Home Battery: Garage, Utility, Loft or Outside Wall
The position is settled at survey and it sets the separation, the cable run and the ambient the warranty is written against. Occasionally it ends the job.
20 min read11 sections10 calculators2026-08-31
Renewables
Siting an Air Source Heat Pump So It Stays Permitted Development
Picking the unit position before the quote: the conditions that keep it permitted development, the noise test done from next door, and the base under it.
20 min read11 sections8 calculators2026-08-31
Gas
Siting a Replacement Boiler: Flue Terminal and Condensate
A swap is positioned from outside in: terminal clearances and the fall to a drain settle which wall the appliance can hang on, long before the old case comes off.
21 min read13 sections9 calculators2026-08-31
Electrical
Sizing a Branch Circuit
Size a branch circuit the way it actually gets sized: from the appliance nameplate back to the panel, one constraint at a time.
10 min read9 sections9 calculators2026-08-28
Renewables
Sizing an Off-Grid Battery Bank
A bank is sized by the night it has to survive and the week it cannot recharge in. Measure both before anyone quotes you a kilowatt-hour.
16 min read9 sections8 calculators2026-08-31
HVAC
Sizing a Perimeter Office Zone
The reheat coil at a glazed bay is sized by the wall in front of it — area-weighted U-factor first, minimum airflow second, coil duty last.
19 min read10 sections11 calculators2026-08-31
Heating
Sizing Radiators, at Boiler and at Heat-Pump Temperatures
A radiator is sized twice: against what the room loses, and against a catalogue figure measured with water hotter than the system will ever run.
21 min read12 sections18 calculators2026-08-31
Site services
Sizing a Septic Drain Field
Every dimension of a septic drain field descends from one measured percolation rate — how to take it, defend it, and protect it on site.
10 min read8 sections6 calculators2026-08-28
Electrical
Sizing a Standby Generator
A standby set is sized by the worst starting instant on the panel, not by the tidy sum of running watts.
11 min read9 sections7 calculators2026-08-28
Plumbing
Sizing Domestic Hot Water
Domestic hot water systems are sized by the worst sixty minutes a building sees, not by the gallons it burns over a whole day.
12 min read7 sections6 calculators2026-08-28
Renewables
Sizing a Solar Water Heater
A solar water heater is sized to the summer rather than the year, so the collector, the store and the backup heater are three decisions, made in that order.
14 min read7 sections8 calculators2026-09-25
Plumbing
Sizing a Water Meter and Backflow Preventer
The meter size box on a utility application is a twenty-year charge, and the relief port under the assembly decides how big the drain beneath it must be.
18 min read12 sections10 calculators2026-08-31
Water supply
Sizing and Plumbing a Water Softener
A softener is sized twice over: the grains a household burns between regenerations, and the flow its valve passes with three fixtures open.
19 min read8 sections9 calculators2026-08-31
Gas
Sizing Gas Piping
Sizing a gas system means walking the one route to the most distant appliance and spending its pressure allowance leg by leg.
10 min read9 sections6 calculators2026-08-28
Plumbing
Working Out How Many WCs a Building Needs
Occupancy, the fixture table and the accessible rooms are three separate counts, and the floor area they add up to is what really decides the core.
19 min read11 sections9 calculators2026-08-31
Electrical
Getting the Incoming Electricity Supply Upgraded
Reading the cut-out before you promise anything, working out the capacity the network application is really asking for, and living with the answer.
19 min read12 sections13 calculators2026-08-31
HVAC
Venting a Commercial Kitchen Hood
A commercial hood captures only what the replacement air allows, so size the make-up air, then the exhaust, duct and fan around it.
12 min read9 sections7 calculators2026-08-28
Electrical
Wiring a Motor Circuit
A motor branch circuit carries four separate duties, and the device that guards against a short circuit is deliberately too big to catch an overload.
19 min read12 sections10 calculators2026-08-30
Electrical
Where Electrics Can Go in a Bathroom
The zones settled before the boards go on: what may sit over a bath, how far a socket has to stand off, and what the fan, mirror and mat need.
20 min read12 sections9 calculators2026-08-31

Safety and compliance22 guides

Passive fire protection
Putting Boxes and Joints Into a Fire-Rated Wall
A rated partition carries a fixed allowance of openings and one moving joint at its head, and two trades spend it without ever seeing each other's tally.
16 min read8 sections10 calculators2026-08-31
Accessibility
Building an Accessible Ramp
A ramp is one fixed vertical rise divided among runs, landings and handrails - spend that slope allowance before the first form board goes down.
11 min read8 sections9 calculators2026-08-28
Passive fire protection
Building a Rated Shaftwall
Shaftwall is the one rated assembly built entirely blind — every panel, stud and screw has to land from the corridor side alone.
13 min read9 sections8 calculators2026-08-28
Fire safety
Choosing a Detection Category and Spacing the Detectors
The category is a scope decision someone else makes in a sentence. Turning it into heads on a ceiling is radius arithmetic, and the radius is not the area.
21 min read10 sections11 calculators2026-09-22
Passive fire protection
Fire Doors and the Escape Route for a Loft Conversion
Adding a third storey turns the stairwell into the only way out, and the enclosure that protects it runs from the new landing down to the front door.
19 min read11 sections12 calculators2026-08-31
Passive fire protection
Fire Protecting Steel to Its Section Factor
The period is a property of the building and the thickness is a property of the member. How to build the section factor column the applicator is waiting on.
21 min read11 sections10 calculators2026-08-31
Passive fire protection
Firestopping Penetrations
Every penetration is a defeat of an assembly that was tested whole — how to name what was breached and install the listed system that puts it back.
12 min read9 sections8 calculators2026-08-28
Passive fire protection
Fitting Cavity Barriers in a Ventilated Rainscreen
A cavity barrier is continuous or it is nothing, and continuity is settled at every rail that crosses it rather than along the metres between them.
19 min read10 sections13 calculators2026-08-31
Passive fire protection
Hanging a Fire Door to the Gap Tolerances
The inspector arrives with a gap gauge rather than a spirit level, so the millimetres round the leaf, the seal runs and the latch are the whole job.
19 min read10 sections9 calculators2026-08-31
Passive fire protection
Putting Fire Dampers Into Ductwork
A fire damper is a piece of the wall that happens to move, and the sleeve, the angles and the access panel are what keep it in the right plane.
20 min read10 sections12 calculators2026-08-31
Fire safety
Putting a Rising Main Into a Tall Building
Height alone decides whether a fire main can stay empty, and the wet answer arrives with a pump, a tank and a rated room nobody costed.
20 min read10 sections12 calculators2026-08-31
Lifting
Planning a Crane Lift
Capacity comes off a load chart written for a level test pad, and the ground under the outriggers has to be built to match it.
11 min read8 sections8 calculators2026-08-28
Rigging
Rigging a Multi-Leg Lift
A four-leg bridle does not divide by four, and the angle it hangs at is set by the sling lengths on the racking rather than by the pick sheet.
18 min read8 sections6 calculators2026-08-31
Pre-construction
Working Out Whether the Job Needs a Party Wall Notice
Three works on one extension, three limbs of the Party Wall etc. Act, two different clocks — and the geometry that decides whether the dig is notifiable.
22 min read11 sections10 calculators2026-08-31
Site safety
Edge Protection and Fall Distance
Fall clearance is a budget — free fall, absorber deployment, harness stretch, anchor movement and margin all spend it before the worker stops.
12 min read10 sections6 calculators2026-08-28
Fire safety
Siting Smoke, Heat and CO Alarms After an Appliance Change
The count is the easy half. What decides whether an alarm sounds in time is the room it hangs in and how far it stands from the appliance.
19 min read7 sections9 calculators2026-08-31
Vertical transport
Sizing a Lift Hoistway and an Escalator Well
A hoistway is four separate reservations rather than one rectangle, and a wellway is a hole whose length the rise settles long before the truss exists.
17 min read10 sections9 calculators2026-08-31
Fire safety
Sizing Exits, Doors and Travel Distance for a Floor
A floor plate becomes an occupant load, the load becomes a number of exits and a width per exit, and the last check is how far anyone has to walk.
20 min read12 sections12 calculators2026-08-31
Fire safety
Fire-Rated Glazing: Integrity, Insulation and the Gap Around It
Fire-rated glazing is bought as a listed assembly. What the mark on the corner records, and why the void around the lite is not slack to pack out.
18 min read11 sections9 calculators2026-08-31
Fire safety
Sprinklering a Racked Warehouse
Commodity class, arrangement and the top of storage decide whether a ceiling array can do it alone — and the fallback is bought once and paid for daily.
24 min read12 sections10 calculators2026-09-01
Site safety
Tying a Scaffold to a Facade Without a Bespoke Design
What keeps a facade scaffold inside a standard compliance sheet, what pushes it out to a designed job, and what sheeting does to the tie schedule.
19 min read9 sections13 calculators2026-08-31
Fire safety
Ventilating a Car Park for Smoke
Whether a deck ventilates itself through openings on opposing faces or needs fans rated to run hot is one page of arithmetic that decides the whole scheme.
19 min read11 sections9 calculators2026-08-31

Sustainability and compliance2 guides

Energy
Auditing a Home's Electricity Use
A doubled electricity bill is a price change, the weather, a new load or a fault. Telling which needs a year of kilowatt-hours, not a wattmeter.
21 min read9 sections11 calculators2026-08-31
Sustainability
Reporting Operational Carbon and Recycled Content
One box wants last year's electricity as tonnes of CO2e, the next wants recycled content as a share of materials spend. Different evidence, different rules.
17 min read10 sections8 calculators2026-08-31

Estimating and project control37 guides

Contract administration
Agreeing a Deposit and Stage Payments
A builder wants a third of the price before anything is dug. What that money is buying, and what every payment after it has to be tied to on site.
20 min read9 sections9 calculators2026-08-31
Contract administration
Applications for Payment, and the Notices That Follow
Application nine went in five weeks ago and nothing has come back. Whether a valid pay less notice ever existed, and what falls due if it did not.
25 min read11 sections10 calculators2026-08-31
Estimating
Costing a House From Plot to Keys
The plot goes to best and final on Friday and the rate you were quoted is a build rate. Working back from a lending ceiling to what the land can be worth.
21 min read10 sections12 calculators2026-08-31
Estimating
Building Up a Unit Rate
A rate is a quotient, and the quantity underneath it was measured by somebody else to rules you have not read. Everything else is the easy half.
21 min read9 sections11 calculators2026-08-31
Materials buying
Buying Bulk Material by the Load
Three suppliers quoting per load, per tonne and per cubic yard, reduced to one rate you can actually compare — and how much to order once the allowance is honest.
17 min read9 sections12 calculators2026-08-31
Property finance
Improvements That Come Back at Resale
One budget, two quotes. Price both at the same figure to read the gap, then cost the reassessment and the sum insured that quietly follow the winner.
18 min read7 sections8 calculators2026-08-31
Programme
Delay, Notice and Extension of Time
A fortnight lost to weather and a late instruction. Which of them buys time, which also buys money, and the notice that has to go before either does.
18 min read12 sections9 calculators2026-08-31
Estimating
Reading Three Builder Quotes That Are Not the Same Job
The gap between the low price and the high one is mostly scope, not greed. How to level three quotes onto one sheet before anyone starts.
20 min read9 sections10 calculators2026-08-31
Estimating
Costing a Bathroom by Fixture and Wet Area
A bathroom is priced through a fixture count and two areas measured to different rules. Floor area is not one of them, and the leak is not a saving.
19 min read10 sections12 calculators2026-08-31
Estimating
Extension or Loft: The Cheapest Extra Bedroom
Two schemes, two totals, and the only comparison that means anything: what each one costs per square metre you can actually stand up in.
21 min read9 sections12 calculators2026-08-31
Estimating
Costing a Kitchen: Runs, Worktops and What Is Behind Them
A kitchen supplier prices the part that unscrews. Here is how to cost the circuits, the waste run and the floor that the doors will outlive.
20 min read10 sections12 calculators2026-08-31
Property finance
Renting or Buying: The Break-Even Years and the Tax on the Way In
A job that might move in three years turns transfer tax and selling fees into the whole decision. How to price the round trip and find the break-even year.
20 min read10 sections9 calculators2026-08-31
Estimating
DIY or Trade: Costing Your Own Time and the Tools
Fourteen days off is about six working days once the calendar is honest. How to price your own hours against a quote, and each tool against its hire ticket.
19 min read8 sections8 calculators2026-08-31
Property finance
Remortgaging: The Payment, the Fees and the Break-Even Month
A fixed rate ends in four months and the offer on the table carries an arrangement fee. How to pick the right baseline and find the month the fee is repaid.
18 min read11 sections8 calculators2026-08-31
Property finance
Paying for the Work: Equity, Loan or Savings
The quote is bigger than the savings. Secured borrowing buys a cheaper rate and a longer rope; a short unsecured loan costs more a month and less in total.
20 min read9 sections9 calculators2026-08-31
Tax
Getting the VAT Rate Right on Building Work
Standard, five per cent or zero is not the client's accountant's decision. What earns the lower rate, and what has to be in the file four years later.
23 min read10 sections10 calculators2026-08-31
Contract administration
Instructing and Pricing a Variation
The client wants different doors and the bifold is already on order. What has to be written, priced and dated before anyone telephones the fabricator.
22 min read10 sections9 calculators2026-08-31
Insurance
Insuring the Works and the Existing Structure
Two property risks share one wall. Who insures a half-built extension, who insures the house it is bolted to, and what a household policy does once the roof is open.
21 min read10 sections8 calculators2026-08-31
Estimating
Pricing a Deck: Boards, Rail, Footings and Stairs
Four price lists, one deck: board feet for the frame, metres for the rail and fascia, a rate per hole and a rate per riser.
20 min read9 sections14 calculators2026-08-31
Contract administration
Pricing a Variation Before It Is Instructed
The drawing changed with the floor already up. How to price the extra against contract rates fixed months ago and a merchant's list that has moved since.
20 min read7 sections8 calculators2026-08-31
Estimating
Provisional Sums, PC Sums and Allowances
Half a fixed price can be placeholders. What a provisional sum is really holding, and what the total does on the day the real figure arrives.
21 min read9 sections10 calculators2026-08-31
Business of contracting
Pricing Your Own Work: Markup, Margin and Overhead
The van, the insurance and every hour nobody pays for have to come out of the jobs you win. The divisions to do before you write the rate.
22 min read11 sections9 calculators2026-08-31
Contract formation
Putting a Written Contract Behind a Domestic Job
The gang is booked for Monday and nothing is signed. What has to exist on paper first, and which of it you can never get back once the work starts.
22 min read11 sections10 calculators2026-08-31
Tax
Reclaiming VAT on a Self-Build
One claim, six months from completion, no second attempt. What the DIY Housebuilders Scheme refunds, what it never could, and what to fix before you file.
23 min read11 sections10 calculators2026-08-31
Tax
Running CIS Deductions on a Subcontractor Payment
A subcontractor's invoice and a pay run on Friday. What the percentage actually comes off, and why the rate is not yours or theirs to choose.
19 min read10 sections9 calculators2026-08-31
Materials buying
Ordering Long-Lead Items Back From the Fix Date
Six weeks from first fix and the windows are not ordered. Finding the last honest order date, and the four moves left when it has already gone.
22 min read10 sections10 calculators2026-08-31
Project controls
Sequencing the Trades on a Renovation
Which waits on a refurbishment are physical, which belong to an inspector, and which are only habit — and the four moments the house cannot take back.
23 min read12 sections12 calculators2026-08-31
Business of contracting
Setting a Day Rate the Business Survives
A day rate is a year of costs divided by a diary. The count of days you can genuinely sell is what decides whether the number works.
20 min read7 sections7 calculators2026-08-31
Estimating
Setting a Renovation Budget That Holds
Three quotes for one kitchen can sit eleven thousand apart. The spread is risk somebody priced, and it decides your overage and contingency.
19 min read8 sections12 calculators2026-08-31
Contract administration
Settling the Final Account
Contract sum, variations, provisional sums, dayworks, payments and retention have to end as one figure. The order that reconciliation runs in, and what it closes.
24 min read10 sections13 calculators2026-08-31
Estimating
Taking Off a Whole House
Centre line, outside face, inside face or core: which measurement each trade is ordered from, where openings come off, and where to round.
7 min read6 sections12 calculators2026-10-10
Estimating
Taking Off Quantities From a Drawing Set
A plan set describes a finished building, never a delivery. The sweep that turns fourteen PDF sheets into an order a merchant can actually pick.
20 min read10 sections15 calculators2026-08-31
Project controls
Knowing Whether a Job Is Ahead or Behind
Three certificates say two-fifths of the job; the ledger says nearly half has gone. What the third valuation can tell you, and what it cannot.
19 min read9 sections8 calculators2026-08-31
Property finance
Borrowing Power: Income, Deposit and the LTV Bands
Income sets one ceiling and the deposit sets another. The lower one is your price, and the gap to the next LTV band is plain arithmetic.
20 min read8 sections8 calculators2026-08-31
Estimating
Writing a Quotation That Holds
A price accepted eleven weeks after it was sent. What the document has to say on the day you write it so the figure is still yours in June.
22 min read9 sections9 calculators2026-08-31
Contract administration
Retention, and Getting the Second Half Back
Five per cent has come off every certificate for a year. What the held balance really is, when half falls due, and what has to happen for the rest.
22 min read10 sections10 calculators2026-08-31
Estimating
Pricing the Preliminaries on a Tender
The measured work is priced and the prelims column is empty. Resourcing supervision, plant and site services off the bar chart instead of guessing a percentage.
25 min read10 sections12 calculators2026-08-31

Specialist trades5 guides

Fixings
Anchoring Into Concrete and Masonry
Every concrete anchor drags a cone of substrate with it — edge distance, spacing and embedment are all arguments about that cone.
12 min read9 sections8 calculators2026-08-28
Acoustics
Stopping Sound Through a Partition: Mass, Gaps and Decoupling
The open-area budget a partition gets to spend, what a doubling of board actually buys, and why the door decides the number.
18 min read8 sections9 calculators2026-08-31
Fixings
Fixing Heavy Things to a Plasterboard Wall
A 40 kg screen on a swung-out arm is a lever, not a weight — so this is about reaching timber, rating a cavity fixing, or letting a pattress in.
18 min read9 sections8 calculators2026-08-31
Acoustics
Isolating Sound Through a Partition
A path-by-path hunt for flanking on a separating wall, from the perimeter bead to the plenum, before anyone argues about board.
13 min read9 sections8 calculators2026-08-28
Acoustics
Stopping Impact Noise Between Floors
A gym going in over occupied offices: what a floating sports floor can reach, what an isolated ceiling has to finish, and what neither of them touches.
14 min read8 sections9 calculators2026-08-31

What these are, and what they are not

A quantity is the easy half. Concrete is ordered by volume and fails by curing; a pavement is priced by tonnage and fails at the joint; an air conditioner is bought by capacity and fails by being too large for the house it was bought for. None of that is visible in the number, and none of it is arithmetic — which is why it lives here rather than on the calculator pages or in the methodology.

The methodology pages cover the mathematics behind the calculators; these cover the site work. Where a guide reaches a decision rather than a quantity, the comparisons set the options side by side, and Project Builder collects the results into one costed estimate you can price and export.

What each guide tries to be specific about: the order operations actually happen in, the tolerances that decide whether the next trade can work, the measurement that predicts whether the work lasts, and the failure that shows up a season later rather than on the day. Where a figure varies by jurisdiction, the guide says so and names what governs it instead of publishing a number that would be wrong somewhere.

These are written for people who already work in the trade, so they assume the vocabulary and skip the introductions. They are guidance rather than specification: local codes, the engineer of record and the manufacturer’s instructions govern wherever they differ.