Foundation Drainage Board (Dimple Mat) Takeoff
The dimpled drainage board (dimple mat / composite drainage sheet) to cover a below-grade foundation wall over the waterproofing, ordered by the roll -- it relieves hydrostatic pressure to the footing drain and protects the membrane during backfill. Area = perimeter x average below-grade height; rolls = ceil(area x (1 + waste) / roll coverage); plus a top-edge termination bar per perimeter. A 150 ft perimeter, 8 ft below grade is 1,200 sf, so at a 4 x 50 ft (200 sf) roll with 10% waste it takes 7 rolls plus ~150 lf of termination molding. The dimples face the WALL so the air gap sits against the membrane. Order the termination bar, corners, and butyl tape separately and lap per the maker's detail. A material-ordering estimate; the roll size and lap, the assembly detail (membrane below, footing drain per IRC R405), and the AHJ govern.
Formula and source
wall_area_sf = perimeter_ft x below_grade_height_ft; roll_coverage_sf = roll_width_ft x roll_length_ft; rolls = ceil(wall_area_sf x (1 + waste_pct/100) / roll_coverage_sf); termination_lf = perimeter_ft.
Foundation drainage board (dimple mat) material takeoff (area over roll coverage), by name; the product roll size and lap, the assembly detail, and IRC R405 (foundation drainage) and the AHJ govern.
Audience
This tile is built for trades and the adjacent professions in the Carpentry and Construction group. The interactive calculator runs entirely in your browser. No account, no fee, no advertising, no tracking.
Related tools
Posture
Rough Logic answers the math question the working professional asks on the job. The site is a calm, fast, ad-free, account-free, ever-free reference. It does not interpret code. It does not replace the licensed professional. It does not store your inputs. The Authority Having Jurisdiction governs all installations and inspections.