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.

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.

The takeoff is public first-principles (wall area over the roll coverage); the roll size comes from the product data sheet and the dimensions from the foundation.

Estimate. AHJ and licensed professional govern.

Field names used by the API: perimeter_ft, below_grade_height_ft, roll_width_ft, roll_length_ft, waste_pct, wall_area_sf, rolls, termination_lf

• Area over roll coverage area = perimeter x below-grade height; rolls = ceil(area x (1 + waste) / roll coverage); termination bar per perimetermaterial-takeoff practice
• Orientation and detail dimples face the wall (air gap against the membrane); relieves hydrostatic pressure to the footing drain (IRC R405); lap and accessories per the makerIRC R405 / product data sheet