Housewrap (WRB) Rolls, Cap Fasteners, and Seam Tape
Housewrap (weather-resistive barrier) takeoff: rolls = ceil(area x (1 + overlap + waste) / roll coverage); cap fasteners = ceil(area x fasteners per sf); seam tape = area / roll width. 4,000 sf of wall on 9 x 150 ft rolls (1,350 sf) at 10% is 4 rolls, 2,000 cap fasteners, and 444 LF of tape; an 8,000 sf job is 7 rolls, 4,000 fasteners, and 889 LF. The WRB is the drainage plane behind the cladding; the cap spacing and flashing tape follow the manufacturer. Distinct from the under-slab vapor-barrier-rolls.
Formula and source
rolls = ceil(wall_area_sf x (1 + overlap_waste_pct/100) / roll_coverage_sf); cap_fasteners = ceil(wall_area_sf x fasteners_per_sf); seam_tape_lf = wall_area_sf / roll_width_ft.
Housewrap takeoff identity by name (rolls over coverage with lap and waste; cap fasteners at an area density; seam tape one seam per roll width); first-principles arithmetic.
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