Job takeoff
Cavity wall insulation (retrofit fill) takeoff
Fill a closed wall from outside: a masonry cavity blown with mineral wool or bead, or the stud bays of a framed wall dense-packed with cellulose (drill and fill), with the ground sheeted and the frames masked, and the bags or bales of fill with the wall area, mass and holes in their working, the survey, the vent sleeves, the drilling, the making good and the spillage test listed, the wall's suitability flagged and nothing certified.
A takeoff is the trade word for the shopping list a job produces — every material, and how much of each, worked out by its own cited calculator.
- 5Measurements in
- 2Trades out
Choose the build-up
Each layer changes the materials below; the dimensions stay the same.
Compare one layer at these dimensions, with the rest of the build-up held as you have it:
Give the job once
Every figure on the right follows these, in the units you choose.
Been given a quote for this job?
Paste it into the cavity wall insulation quote check: each line is read against these same calculators — what it leaves out, what it adds, and what to ask.
Check the quoteEvery trade, from those dimensions
then change a dimension, and each line shows what moved.
| Trade | Quantity | |
|---|---|---|
Masking and protection materialsMasking and Protection Materials CalculatorThe masking page taken out of doors. Its floor area here is the strip of ground sheeted along the foot of every wall filled, about 1 m (3 ft) wide, over the paths, beds and gullies the drilling dust and any escaped fill fall on; its openings are the windows and doors, masked with tape round all four sides of each at their average size. Nothing is taped along the wall. It is the second row both walls run: everything else on this job but the fill is listed work.
Why this quantity?
Resting on
Change any other figure on the Masking and Protection Materials Calculator | 3 items | |
Cavity fill, blown-in bead, wool or dense-pack cellulose (bags or bales)Cavity Wall & Stud Bay Insulation Fill CalculatorBags, or bales to a British installer, for the walls' net face, their length times their height less the windows and doors, at the installed density and bag weight the wall you chose sets: a 65 mm (2 9/16 in) masonry cavity blown with Supafil 34 at its certificate's 25 kg/m³ (1.56 lb/ft³) from 15.5 kg (34.2 lb) bales, or 2x4 stud bays 3 1/2 in (89 mm) deep, dense-packed with cellulose at 3.5 lb/ft³ (56 kg/m³) from 30 lb (13.6 kg) bags, with the studs' share of the face taken off. A quote prices this row by the area of wall, which the working prints beside the bags as the page's own row, ‘Wall area to fill, openings deducted’, with the mass, the volume and a grid of the holes. The holes are drilled and made good as listed work. This row's own work ends with the checks that the fill is complete and that no vent or flue took any. Each product figure is the certificate's or the chart's, for the reader to replace with the product the installer blows.
Why this quantity?
Resting on
The waste allowance: the calculator's working figure, a trade convention. Change any other figure on the Cavity Wall & Stud Bay Insulation Fill Calculator | 30 bags | |
Masking and protection materialsMasking and Protection Materials CalculatorThe masking page taken out of doors. Its floor area here is the strip of ground sheeted along the foot of every wall filled, about 1 m (3 ft) wide, over the paths, beds and gullies the drilling dust and any escaped fill fall on; its openings are the windows and doors, masked with tape round all four sides of each at their average size. Nothing is taped along the wall. It is the second row both walls run: everything else on this job but the fill is listed work.
Why this quantity? | 3 items | |
Cavity fill, blown-in bead, wool or dense-pack cellulose (bags or bales)Cavity Wall & Stud Bay Insulation Fill CalculatorBags, or bales to a British installer, for the walls' net face, their length times their height less the windows and doors, at the installed density and bag weight the wall you chose sets: a 65 mm (2 9/16 in) masonry cavity blown with Supafil 34 at its certificate's 25 kg/m³ (1.56 lb/ft³) from 15.5 kg (34.2 lb) bales, or 2x4 stud bays 3 1/2 in (89 mm) deep, dense-packed with cellulose at 3.5 lb/ft³ (56 kg/m³) from 30 lb (13.6 kg) bags, with the studs' share of the face taken off. A quote prices this row by the area of wall, which the working prints beside the bags as the page's own row, ‘Wall area to fill, openings deducted’, with the mass, the volume and a grid of the holes. The holes are drilled and made good as listed work. This row's own work ends with the checks that the fill is complete and that no vent or flue took any. Each product figure is the certificate's or the chart's, for the reader to replace with the product the installer blows.
Why this quantity? | 10 bags |
Estimates, not a quote. Each row gives its base, the allowance on top, the adjusted figure and what to order; change an allowance on the row, or open its reasoning to see every figure it rests on. A trade's own page carries what it does not cover — open the one you are about to order against.
Labour and programme
Person-hours for the rows going in, from trade rules of thumb: a range for each piece of work, never a price.
- Masking and protection materials0.9 h (0.4–1.8)
About 0.9 person-hours in the rows that carry them, between 0.4 and 1.8.
Trade by trade
- Labourer1 labourerunder a quarter of a day
About under a quarter of a day, one trade after another at eight hours a day. Left out: drying and curing, deliveries, inspections, trades overlapping.
1 row carries no hours of its own
- Cavity fill, blown-in bead, wool or dense-pack cellulose (bags or bales): Cavity wall insulation is not rated here: a specialist installer blows it, under a guarantee scheme in the UK, and prices it as supply and fit per house or per area of wall, so an hourly figure would invite a comparison no quote makes.
Labour and programme
Person-hours for the rows going in, from trade rules of thumb: a range for each piece of work, never a price.
- Masking and protection materials0.9 h (0.4–1.8)
About 0.9 person-hours in the rows that carry them, between 0.4 and 1.8.
Trade by trade
- Labourer1 labourerunder a quarter of a day
About under a quarter of a day, one trade after another at eight hours a day. Left out: drying and curing, deliveries, inspections, trades overlapping.
1 row carries no hours of its own
- Cavity fill, blown-in bead, wool or dense-pack cellulose (bags or bales): Cavity wall insulation is not rated here: a specialist installer blows it, under a guarantee scheme in the UK, and prices it as supply and fit per house or per area of wall, so an hourly figure would invite a comparison no quote makes.
Setups you have saved
The build-up, the dimensions and any allowance you changed — kept on this device, and reusable on any job. Your prices are not copied in: they stay in your price book, so a setup never holds a stale one.
How far does a budget go?
At your own prices, with this build-up unchanged.
About this job
A cavity wall can be insulated without touching the inside of the house: a row of holes is drilled from outside and the closed void behind the face is filled through them. What that void is depends on where the house stands. In Britain, Ireland and much of Europe it is a masonry cavity, two leaves of brick or block with a clear gap between, blown with mineral wool or bonded polystyrene bead through holes about 22 mm (7/8 in) across, drilled into the mortar joints on the pattern the system's certificate draws. In North America it is drill-and-fill: a timber-framed wall's closed stud bays dense-packed with cellulose down a fill tube, through holes drilled in the sheathing behind a course of siding that is lifted and put back.
The rows measure the fill and the protection; the rest is listed. The fill row counts the bags (bales, to a British installer) for the walls' net face, their length times their height less the windows and doors, at the installed density and bag weight the wall you choose sets, and its working prints the wall area beside them, with the mass, the volume and a grid of the holes. A quote prices this job by the area of wall, so that is the figure to hold against it. The protection row is the dust sheets along the foot of every wall filled and the tape round each window and door. The survey, the vent sleeves, the drilling, the making good and the spillage test are work this page lists without measuring.
The units pick the wall. With metric showing, it opens on a 65 mm (2 9/16 in) masonry cavity filled with Supafil 34 blown mineral wool at its certificate's 25 kg/m³ (1.56 lb/ft³) from 15.5 kg (34.2 lb) bales; with imperial showing, on 2x4 stud bays, 3 1/2 in (89 mm) deep at 16 in (406 mm) centres, dense-packed with cellulose at 3.5 lb/ft³ (56 kg/m³) from 30 lb (13.6 kg) bags. Either is one choice away, and a reader in Canada, whose page opens in metric, chooses the stud wall there. Each choice sets all six of the fill page's product figures together, the gap, the studs, the two hole spacings, the density and the bag, so no wall is filled on the other wall's product.
Not every wall should be filled, and this page judges none. The installer's surveyor decides, from a borescope through test holes or a look into each bay: how wide and how clean the cavity is, how exposed the wall is to driving rain, whether a stud bay hides live knob-and-tube wiring, which the US National Electrical Code (Article 394.12) does not allow to be buried in insulation. Old paint on siding in an older US home is tested for lead, or worked lead-safe by a certified firm under the EPA's Renovation, Repair and Painting (RRP) Rule, before it is drilled, and old siding is checked for asbestos cement. Once the walls are filled, each boiler, fire or stove that draws its air from the rooms is spillage-tested by its own engineer, a combustion appliance zone (CAZ) test in North America; and in Britain the installer's guarantee and the notification to building control are named here and never promised.
How each line reads
- Base
- What the calculator gives for these dimensions, before anything is added.
- Allowance
- Cutting waste, a lap or spare stock — named, with where it comes from, and changeable on the row.
- Adjusted
- The base with its allowance on top.
- Order
- What to buy: the adjusted figure in whole boards, bags, rolls or lengths.
The order this happens in
Quantities do not tell you the sequence, and on this job the sequence is where the money goes wrong.
- Have the installer's surveyor look at every elevation, through a borescope in a masonry cavity or into each stud bay for blocking, knob-and-tube wiring and what the siding is made of; have old paint on the siding tested for lead and old siding or panels checked for asbestos, and the notification or permit arranged.
- Set up the ladders, or a tower where the top rows are out of a ladder's safe reach, and sheet the ground along the foot of every wall to be filled, with the windows and doors masked.
- In a masonry wall, sleeve every air brick and vent that crosses the cavity, brush or close the cavity at the party line of a semi-detached or terraced house, and cover the weep vents over the cavity trays and lintels.
- Drill the holes: into the mortar joints of the outer leaf on the certificate's pattern, with the extra holes under the sills and round the openings; or, in a stud wall, through a lifted course of siding and the sheathing into every bay, and again below each run of blocking.
- Blow the fill in from the lowest row up, hole by hole, until the cavity is full at the density its certificate sets; or dense-pack each stud bay down a fill tube until it takes no more.
- Check that the fill is complete, through a test hole or with a thermal camera in masonry and bay by bay for density in a stud wall, and that no air brick, vent or flue has taken any, then uncover the weep vents.
- Close every hole with a mortar matched to its joints and pointed to their profile, or plug it, refix the lifted siding and touch in the paint; then have each open-flued boiler, fire or stove spillage-tested by the engineer its fuel needs.
- Pick up the drilling dust and any fill that escaped from the paving, sills and gutters, lift the sheets, and hand over the installer's record of the product, its density and the bags used, with the guarantee and the notification in Britain.
What this takeoff does not cover
- Judging the cavity suitable (the installer's call).
- Cavity extraction, taking out an old or failed fill.
- Wall tie replacement or renewal.
- Damp or rain found afterwards (flagged).
- Knob-and-tube rewiring.
- Abatement or encapsulation.
- New cladding boards (re-siding the house).
- Roof-space (attic) work.
- A gable's triangle above the eaves line, unless its area is added to the length as that figure's help says: the fill counts the rectangle below it.
- Repointing the outer leaf, or putting its cracks right, where the survey asks for that first.
- Trickle vents or extract fans that a tighter house may need afterwards.
Quote check
Been given a quote for this job?
Paste it into the cavity wall insulation quote check. Every line of it is read against these same calculators and your measurements. Quantities only, never prices.
What it leaves out
Every line this takeoff has that nothing on the quote reads as.
What it adds
Labour, removal, hire, fees — each named for what it is.
What to ask
One list of questions, ready to copy. Never a verdict.
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Frequently asked questions
- What does the cavity wall insulation takeoff give for a typical job?
- Opened at Length of wall filled, every elevation end to end 22 m · Height filled 4.8 m · Windows and doors in the walls filled 10 · Opening width, average 1.1 m · Opening height, average 1.3 m, it orders: Masking and protection materials, 3 items; Cavity fill, blown-in bead, wool or dense-pack cellulose (bags or bales), 10 bags. Opened at Length of wall filled, every elevation end to end 72 ft · Height filled 15.5 ft · Windows and doors in the walls filled 10 · Opening width, average 3.5 ft · Opening height, average 4.5 ft: Masking and protection materials, 3 items; Cavity fill, blown-in bead, wool or dense-pack cellulose (bags or bales), 30 bags. Every figure follows the dimensions you give it.
- Which calculators does the cavity wall insulation takeoff run?
- 2 calculators, one to a line: Masking and Protection Materials Calculator, Cavity Wall & Stud Bay Insulation Fill Calculator. Each has a page of its own with its formula and its sources; the takeoff runs them all on one set of dimensions.
- What does the cavity wall insulation takeoff leave out?
- 11 things, each named on this page: Judging the cavity suitable (the installer's call); Cavity extraction, taking out an old or failed fill; Wall tie replacement or renewal; Damp or rain found afterwards (flagged); Knob-and-tube rewiring; Abatement or encapsulation; New cladding boards (re-siding the house); Roof-space (attic) work; A gable's triangle above the eaves line, unless its area is added to the length as that figure's help says; Repointing the outer leaf, or putting its cracks right, where the survey asks for that first; Trickle vents or extract fans that a tighter house may need afterwards.
- Can I check a quote for this job against the takeoff?
- Yes. The cavity wall insulation quote check reads a quote's lines against these same calculators and your measurements, and reports what it leaves out, what it adds and what to ask. It reads quantities, never prices.