Solve backwards
How much foundation wall will my protection boards cover?
- 18 sheetsThe example worked below
- Foundation Waterproofing Protection Board CalculatorEvery figure is its own
You have
How much protection board?
Worked by the Foundation Waterproofing Protection Board Calculator at the settings below.
The settings it uses
- Sheet Area
- 32 sq ft
What it will do
576 sq ft of foundation wall
53.5 m²
One foundation wall. Enough for a foundation wall 72 ft long and 8 ft high.
Or several. About 1 foundation wall of the size the Foundation Waterproofing Protection Board Calculator opens on: a foundation wall 67.5 ft long and 8 ft high.
Check it forwards
- Foundation Wall Area
- 576 sq ft
- It asks for
- 18 sheets
- You have
- 18 sheets
The Foundation Waterproofing Protection Board Calculator asks for 18 sheets at that size, and 19 sheets one step larger.
If you had more, or less
Around your amount
Each worked by the Foundation Waterproofing Protection Board Calculator at the same settings.
Half
9 sheets
288 sq ft
a foundation wall 36 ft long and 8 ft high
Yours
18 sheets
576 sq ft
a foundation wall 72 ft long and 8 ft high
Half as much again
27 sheets
864 sq ft
a foundation wall 108 ft long and 8 ft high
Double
36 sheets
1,152 sq ft
a foundation wall 144 ft long and 8 ft high
Common amounts
What each amount of protection board covers
The sizes it is usually sold in, each worked by the Foundation Waterproofing Protection Board Calculator at the settings above.
| You have | It covers | As one foundation wall | Average foundation walls |
|---|---|---|---|
| 6 sheets | 192 sq ft(17.8 m²) | a foundation wall 24 ft long and 8 ft high | under 1 |
| 12 sheets | 384 sq ft(35.7 m²) | a foundation wall 48 ft long and 8 ft high | under 1 |
| 18 sheets | 576 sq ft(53.5 m²) | a foundation wall 72 ft long and 8 ft high | 1 |
| 30 sheets | 960 sq ft(89.2 m²) | a foundation wall 120 ft long and 8 ft high | 1 |
Sheet for sheet, nothing spare
The calculator divides the wall by the sheet and rounds up, with no allowance for cutting around window wells and pipe penetrations or for extra cover at corners and footing turn-downs. Eighteen 4 by 8 foot boards cover 576 square feet, 72 feet of wall 8 feet deep; eighteen metric boards cover 51.8 m², 21.6 m. Rounding up is not an allowance: 50 m² on 2.88 m² boards leaves 1.84 m² spare over the whole job.
The same count for every board
Sheet area is the only property the count uses, so a thin asphaltic hardboard, a dimpled polymer sheet and a rigid insulation panel all return the same number for the same wall. Whether the board's thickness and compressive strength survive the backfill material, the lift depth and the compaction plant is a separate judgement — and it is the one that decides whether the membrane under it survives.
Held on until the backfill
Only boards are counted. The mastic dabs, tape, termination bar and mechanical fixings that hold them against the wall until the backfill is placed are not in the result, and nor are the membrane, the primer or the perimeter drain the board exists to protect. Each is its own line on the order, and each is needed on the same day the board goes up, before the first lift of fill goes in.
How the answer is worked
Nothing here is a second formula. The Foundation Waterproofing Protection Board Calculator runs forwards — a size in, a quantity out — and this page grows its own starting foundation wall in proportion until the quantity it asks for is what you have. Where it rounds up to whole containers, the answer is the largest size before the next one would be needed.
Where the calculator adds an allowance for cuts or breakage when you order, the same allowance comes off here, because it is the same calculator: a stack you already own finishes less than its face value. Where it adds none, neither does this page — the settings beside the answer say which.
Foundation Waterproofing Protection Board Calculator
runs it forwardsCalculate how many protection board sheets are needed to shield a below-grade waterproofing membrane during backfill.
Work out what to buy insteadSolve backwards
Other things you might already have
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How much wall will my mineral wool boards insulate?
Mineral wool board, worked by the Exterior Mineral Wool Board Insulation Calculator.
Solve backwards
Start from what is already in the yard
Paint, sheets, rolls, bags and pieces, each read the other way by the calculator that orders it.
The calculator's own figures
Nothing is estimated twice: the page runs the same calculator you would order with.
The largest size that fits
Where a calculator rounds up to whole containers, the answer stops before the next one.
Both unit systems
Gallons and litres, square feet and square metres, side by side.
Frequently asked questions
- How much foundation wall does 18 sheets of protection board cover?
- At the Foundation Waterproofing Protection Board Calculator's own settings, 576 sq ft (53.5 m²) — a foundation wall 72 ft long and 8 ft high. That is about 1 foundation wall of the size the calculator opens on: a foundation wall 67.5 ft long and 8 ft high. Every figure follows the settings, which you can change in the calculator.
- Do I need protection board over foundation waterproofing?
- Sheet membranes puncture easily on angular fill and under the machine placing it, so a protection board or drainage composite normally goes over them before backfilling, and many coating systems call for one too. The maker's system instructions say which board to use and whether a drainage layer can serve instead.
- How many sheets of protection board for a basement?
- Divide the waterproofed wall area by the sheet area and round up. A basement 30 by 40 feet with walls 8 feet deep has 1,120 square feet, 35 sheets of 4 by 8 feet; in metric, 104 m² takes 37 sheets of 2.88 m² (36.1 rounded up) — before any cutting allowance.
- What size is protection board?
- Common sheets are 4 by 8 feet, 32 square feet (2.97 m²), in North America and 1.2 by 2.4 m, 2.88 m² (31 square feet), elsewhere, which is what this page counts in each system. The calculator accepts sheets from 1 to 6 m² (10.8 to 64.6 square feet), so a protection course supplied as a roll cannot be entered as one unit.