Housewrap (WRB) Rolls, Cap Fasteners, and Seam Tape
Housewrap (weather-resistive barrier) takeoff.
Example
You enter
- Wall area (ft²) 4000
- Coverage per roll (ft²) 1350
- Overlap + waste (%) 10
- Cap fasteners per ft² 0.5
- Roll width / height (ft) 9
You get
- Housewrap rolls 4
- Cap fasteners 2,000
- Seam tape (upper bound) 444.44
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
Scoperolls = ceil(area x (1 + overlap + waste) / roll coverage); cap fasteners = ceil(area x fasteners per sf); seam tape up to area / roll width (an upper bound). 4,000 sf of wall on 9 x 150 ft rolls (1,350 sf) at 10% is 4 rolls, 2,000 cap fasteners, and at most 444 LF of tape; an 8,000 sf job is 7 rolls, 4,000 fasteners, and at most 889 LF. The WRB is the drainage plane behind the cladding; the cap spacing and flashing tape follow the manufacturer. Distinct from under-slab vapor barrier.
Formula or tablerolls = 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.
Source and editionHousewrap takeoff identity by name (rolls over coverage with lap and waste; cap fasteners at an area density; seam tape bounded by the total wrap run, area / roll width); first-principles arithmetic.
Free accessThe takeoff arithmetic is public quantity-survey math; the fastening and flashing follow the manufacturer and code.
What governsEstimate. AHJ and licensed professional govern.
API field nameswall_area_sf, roll_coverage_sf, overlap_waste_pct, fasteners_per_sf, roll_width_ft, rolls, cap_fasteners, seam_tape_lf
- Cap fasteners ~0.5 per ft^2 for a 12 to 18 in grid (default); tighter in high wind per the manufacturerWRB manufacturer
- Roll coverage ~1,350 sf for a 9 x 150 ft roll (default); the product size governsWRB manufacturer