House Wrap Calculator
How many rolls of house wrap a house takes: wall area from the perimeter and height, openings deducted, and the standard roll sizes with the lap allowance in.
House wrap by the roll
House wrap (the weather-resistive barrier that goes under siding) is counted like wallpaper on a building: wall area is the perimeter walked around the house times the wall height, with doors and windows taken back out. The part estimates forget is the laps — horizontal courses overlap about 6 in, corners wrap around, and openings get wrapped and flashed — which together eat roughly a tenth of the material. The calculator folds that lap allowance into the roll count, so the number is an order number, not a bare area.
Wall area = perimeter × height − openings · Wrap needed = wall area ÷ 0.90 (lap allowance) · Rolls = wrap needed ÷ roll coverage (9 × 100 ft = 900 sq ft, 9 × 150 ft = 1,350)
Example: a house with a 140 ft perimeter and 9 ft walls, with 200 sq ft of doors and windows: 1,060 sq ft of wall needs 1,178 sq ft of wrap — 2 rolls of 9 × 100 ft, or a single roll of 9 × 150.
Two heights of thinking to add: gable ends above the top plate need wrap too (the exterior paint calculator's gable method — half the width times the peak height, per gable — adds their area if your gables are tall), and a second story usually wraps easier as two 9 ft lifts than one tall one. Wrap wants its seams taped and its laps shingled — upper courses over lower, so water always meets an overlap pointing down. Keep the roll out of prolonged sun where you can; most wraps have a UV exposure limit measured in months, printed on the wrapper.
Frequently asked questions
How much overlap does house wrap need?
About 6 in on horizontal laps and 12 in at vertical (end) laps is the standard maker instruction, with corners wrapped around rather than cut. Counting laps, tape and the wrapping of openings, a tenth of the material disappears into the details — the allowance built into this calculator's roll count.
Should house wrap go over or under the window flanges?
Both, in sequence — that is what 'shingle-style' means. The wrap below a window tucks under the flange, the wrap above laps over it, so any water on the barrier drains out over the flange, never behind it. Pre-cut openings in an X, fold the flaps in, and tape; the details at openings matter more than the field of the wall.
9 × 100 or 9 × 150 ft rolls — which should I buy?
The square footage per dollar is usually close; choose by handling. The 150 ft roll covers a typical house in one roll with nothing left to store, but it is heavier and two-person awkward on a ladder or in wind. Two 100 ft rolls are the friendlier solo choice, and a spare partial roll covers repairs.
Does house wrap replace flashing?
No. Wrap is the drainage plane; flashing is the metal or membrane work that directs water at roofs, decks, windows and doors. A wrapped house still wants pan flashing at openings and kickout flashing where roofs meet walls. Wrap tucked wrong at a flashing is the classic leak — the shingle order of the layers is the whole game.
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