Footing Drainage Board Calculator
Estimate drainage-board membrane for below-grade foundation walls from wall length, protected height, laps, waste and roll coverage.
Default project preview
3 rolls
Gross wall area
960 ft²
Net protected area
920 ft²
Lap/detail addition
92 ft²
Waste allowance
81 ft²
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Foundation wall length
Enter this project assumption in ft. The current imperial default is 120 ft.
Protected wall height
Enter this project assumption in ft. The current imperial default is 8 ft.
Excluded openings
Enter this project assumption in ft². The current imperial default is 40 ft². Minimum: 0.
Lap/detail allowance
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 50.
Waste allowance
Enter this project assumption in %. The current imperial default is 8 %. Minimum: 0. Maximum: 50.
Usable coverage per roll
Enter this project assumption in ft². The current imperial default is 400 ft².
Price per roll
Enter this project assumption in a unitless value. The current imperial default is 145. Minimum: 0.
How to read the outputs
Gross wall area
before deductions. Default preview: 960 ft².
Net protected area
after openings. Default preview: 920 ft².
Lap/detail addition
seams and transitions. Default preview: 92 ft².
Waste allowance
cuts and damage. Default preview: 81 ft².
Purchased coverage
full rolls. Default preview: 1,200 ft².
Material cost
rolls only. Default preview: $435.00.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Order area = (wall length × protected height − openings) × lap/detail factor × waste factor. Rolls are rounded up from usable roll coverage.
Related tools
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Understand the measurements and assumptions
Use these visible reference guides before changing project inputs or planning allowances.
FAQ
Footing Drainage Board Calculator questions
Should window wells be deducted?+
Deduct only areas that truly will not receive membrane, and add separate detailing allowance around openings.
Does drainage board replace waterproofing?+
No. It typically protects or drains alongside a specified waterproofing or dampproofing layer.
Why use usable roll coverage?+
Published roll area may not account for laps, trimming or damaged edges.