Solve backwards
How much foundation wall will my rolls of waterproofing membrane cover?
- 9 rollsThe example worked below
- Below-Grade Waterproofing Membrane Roll CalculatorEvery figure is its own
You have
How much waterproofing membrane?
Worked by the Below-Grade Waterproofing Membrane Roll Calculator at the settings below.
The settings it uses
- Roll coverage area
- 100 sq ft
What it will do
900 sq ft of foundation wall
83.6 m²
One foundation wall. Enough for a foundation wall 113 ft long and 8 ft high.
Or several. About 1 foundation wall of the size the Below-Grade Waterproofing Membrane Roll Calculator opens on: a foundation wall 107 ft long and 8 ft high.
Check it forwards
- Foundation Wall Area
- 900 sq ft
- It asks for
- 9 rolls
- You have
- 9 rolls
The Below-Grade Waterproofing Membrane Roll Calculator asks for 9 rolls at that size, and 10 rolls one step larger.
If you had more, or less
Around your amount
Each worked by the Below-Grade Waterproofing Membrane Roll Calculator at the same settings.
Half
5 rolls
500 sq ft
a foundation wall 62.5 ft long and 8 ft high
Yours
9 rolls
900 sq ft
a foundation wall 113 ft long and 8 ft high
Half as much again
14 rolls
1,400 sq ft
a foundation wall 175 ft long and 8 ft high
Double
18 rolls
1,800 sq ft
a foundation wall 225 ft long and 8 ft high
Common amounts
What each amount of waterproofing membrane covers
The sizes it is usually sold in, each worked by the Below-Grade Waterproofing Membrane Roll Calculator at the settings above.
| You have | It covers | As one foundation wall | Average foundation walls |
|---|---|---|---|
| 2 rolls | 200 sq ft(18.6 m²) | a foundation wall 25 ft long and 8 ft high | under 1 |
| 5 rolls | 500 sq ft(46.5 m²) | a foundation wall 62.5 ft long and 8 ft high | under 1 |
| 9 rolls | 900 sq ft(83.6 m²) | a foundation wall 113 ft long and 8 ft high | 1 |
| 15 rolls | 1,500 sq ft(139 m²) | a foundation wall 188 ft long and 8 ft high | 1 |
The label's coverage, not the roll's face
The calculator divides the wall by the coverage one roll is rated for — 100 square feet (9.3 m²) by default — and rounds up. Read backwards, nine rolls cover 900 square feet (83.7 m²): about 112 feet (35 m) of wall 8 feet deep. Nothing is added for cutting, so check whether your label's figure already allows for the side and end laps, and use the rating for your roll's width and length.
A wall that will take the sheet
Nothing here asks whether the wall will accept the membrane. Self-adhered and torch-applied sheets bond only to a sound, dry, clean substrate, and most carry a minimum application temperature. Honeycombing, unfilled tie holes, form release left on the face, or concrete too green or too cold all have to be dealt with first — an unbonded sheet is a channel that water can follow behind it.
Protect it before the backfill
Sheet membrane punctures easily on angular fill and under the machine placing it, so a protection board or drainage composite normally goes on over the same area — a separate order, with a page of its own here. Unlike a miscounted roll, a sheet torn during backfilling is buried: it cannot be found or repaired without digging the wall out a second time, which is why the protection is never optional.
How the answer is worked
Nothing here is a second formula. The Below-Grade Waterproofing Membrane Roll 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.
Below-Grade Waterproofing Membrane Roll Calculator
runs it forwardsCalculate how many rolls of below-grade waterproofing membrane are needed for a foundation wall.
Work out what to buy insteadSolve backwards
Other things you might already have
How much house will my rolls of house wrap cover?
House wrap, worked by the House Wrap Calculator.
How big a crawlspace will my vapor barrier rolls cover?
Vapor barrier, worked by the Vapor Barrier Calculator.
How much roof will my rolls of underlayment cover?
Roofing underlayment, worked by the Roofing Underlayment Calculator.
How big a garden bed will my landscape fabric cover?
Landscape fabric, worked by the Landscape Fabric Calculator.
How much floor will my rolls of underlayment cover?
Floor underlayment, worked by the Laminate/Vinyl Plank Floor Underlayment Roll Calculator.
How much eave will my rolls of ice and water shield cover?
Ice and water shield, worked by the Ice & Water Shield 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 9 rolls of waterproofing membrane cover?
- At the Below-Grade Waterproofing Membrane Roll Calculator's own settings, 900 sq ft (83.6 m²) — a foundation wall 113 ft long and 8 ft high. That is about 1 foundation wall of the size the calculator opens on: a foundation wall 107 ft long and 8 ft high. Every figure follows the settings, which you can change in the calculator.
- How many rolls of waterproofing membrane do I need for a basement?
- Add up each wall's length times its depth below grade and divide by the roll's rated coverage. A basement 30 by 40 feet with walls 8 feet deep has 1,120 square feet (104 m²) of wall, which is 12 rolls at 100 square feet (11.2 rounded up), before any cutting allowance.
- How much does a roll of waterproofing membrane cover?
- It varies by product, which is why the calculator asks for it; its default is 100 square feet (9.3 m²) a roll. The label or technical data sheet gives the rated coverage for that roll's width and length — use that figure rather than the roll's face area where the two differ.
- Sheet membrane or a waterproofing coating?
- They solve the same problem differently. A sheet has a factory-controlled thickness but needs laps and a substrate it can bond to; a coating is built to a thickness the applicator controls and follows any shape. Both need a sound, clean wall and protection before backfill. The site's basement waterproofing coating page reads the same wall in gallons or litres.