How this calculator works
House wrap is a water-resistive barrier that goes on the sheathing under the siding. It is hung in horizontal courses from the bottom, each one overlapping the one below, so part of every course is lost to the overlap. The calculator adds the wall and the gable areas, scales them for the overlap, adds the waste and divides by the area of one roll.
Worked example: a house with a 140 ft perimeter, 9 ft walls and two 28 × 8 ft gables is 1,484 ft². A 9 ft roll with a 6 in overlap uses 9 ÷ 8.5 of it, 1,571 ft², and with 10% waste 1,728 ft². That is 2 rolls of 9 × 100 ft (900 ft²), or 2 of 9 × 150 ft (1,350 ft²), or 2 of 10 × 100 ft.
Assumptions and sources
- Assumptions used: 10% waste added; each course overlaps the one below by 6 in; no deduction for windows and doors.
- The International Residential Code asks for a water-resistive barrier lapped at least 2 in at horizontal joints and 6 in at vertical joints, and the wrap maker's instructions rule: some ask for a 6 in lap everywhere, and for the joints to be taped. Hang the courses from the bottom, so that each upper course laps over the one below and sheds water. Roll sizes vary by make, so check the label. Seam tape, cap nails or cap staples, flashing tape for the windows and the sill pan are bought separately.
The formula and a worked example are shown above, so you can check any result by hand. Read how we calculate and check our numbers. Results are estimates for planning: supplier products vary, so check the size printed on the label.
Rolls of house wrap for typical houses
9 ft tall walls, 6 in laps, 10% waste, with two gables 8 ft high. 9 ft × 100 ft and 9 ft × 150 ft rolls.
| Footprint | Perimeter | 9 × 100 ft rolls | 9 × 150 ft rolls |
|---|---|---|---|
| 24 × 30 ft | 108 ft | 2 | 2 |
| 28 × 40 ft | 136 ft | 2 | 2 |
| 30 × 50 ft | 160 ft | 3 | 2 |
| 40 × 60 ft | 200 ft | 3 | 2 |
Tips before you buy
- Hang the wrap from the bottom up, with each upper course over the lower one, so water runs down the face of the wrap and never behind a joint.
- Wrap the corners in one piece where you can, and take it past each corner by about a foot, so there is no joint at the most exposed place.
- A taller roll (9 or 10 ft) means fewer horizontal joints: choose the one that gets a full course on each story.
- Wrap over the window and door openings, then cut an "I" and fold the flaps into the opening, and flash it as the window maker says.
- Cover the wrap soon after it goes up: it is rated for months in the sun, not years.
Tools & materials for this project
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Frequently asked questions
How many rolls of house wrap do I need?
Work out the wall and gable area, add about 6% for the overlaps and 10% for waste, and divide by the roll area. A house with 1,484 ft² of wall needs 2 rolls of 9 × 100 ft (2 rolls of 9 × 150 ft).
What sizes does house wrap come in?
Common rolls are 9 ft × 100 ft (900 ft²), 9 ft × 150 ft (1,350 ft²), 10 ft × 100 ft and 10 ft × 150 ft, plus narrower rolls for small jobs.
How much should house wrap overlap?
The International Residential Code asks for at least 2 inches at horizontal joints and 6 inches at vertical joints. Many makers ask for 6 inches throughout and for the seams to be taped.
Do I take the windows and doors off the area?
No. The wrap goes over the openings and is cut and folded in, so the wall area is the full area. Take them off only if you are sure you will not wrap over them.
Should house wrap go on horizontally or vertically?
Most makers say horizontal, from the bottom up, so that each joint sheds water onto the course below. Follow the instructions for your product.
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Related calculators & guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.