Siding Square Footage Calculator
Calculate net siding area by subtracting windows, doors, and other openings from gross wall area. Add waste factor for accurate material ordering.
House Wrap Calculator
Calculate house wrap (weather barrier) rolls needed for exterior walls. Estimates from gross wall area with overlap allowance for Tyvek, Typar, and similar products.
ft
ft
%
Gross Wall Area⧉
1,440 sq ft
Roll Coverage (nominal)⧉
900 sq ft
Effective Coverage⧉
792 sq ft
After 12% overlap
Rolls Needed⧉
2
Total Roll Area⧉
1,800 sq ft
Planning notes, formulas, and examples
About the House Wrap Calculator
House wrap (weather-resistant barrier or WRB) is installed over the exterior sheathing and under the siding to prevent water infiltration while allowing water vapor to escape. Products like Tyvek HomeWrap, Typar HouseWrap, and ZIP System sheathing tape are common choices in residential construction.
This calculator determines how many rolls of house wrap are needed based on the gross wall area (not net — house wrap covers the entire wall surface, including behind windows and doors, since it's part of the waterproofing system). It adds overlap allowance because house wrap must overlap 6–12 inches at horizontal seams and 6 inches at vertical seams.
House wrap is typically sold in 9-foot by 100-foot or 9-foot by 150-foot rolls. The overlap requirement means actual coverage per roll is 10–15% less than the roll's nominal area.
When This Page Helps
House wrap coverage is reduced by required overlaps. This calculator accounts for the overlap loss to ensure you order enough rolls to cover all exterior walls without gaps in the weather barrier.
How to Use the Inputs
- Enter the house perimeter.
- Enter the wall height (sill to eave).
- Select the roll size (9×100 or 9×150).
- Enter the overlap allowance (typically 12–15%).
- Review the roll count.
Formula used
Gross Wall Area = Perimeter × Wall Height
Roll Coverage = Roll Width × Roll Length
Effective Coverage = Roll Coverage × (1 − overlap%/100)
Rolls = Gross Wall Area / Effective Coverage (round up)Example Calculation
Result: 2 rolls
Gross wall area = 160 × 9 = 1,440 sq ft. Roll coverage = 9 × 100 = 900 sq ft. Effective coverage = 900 × 0.88 = 792 sq ft. Rolls = 1,440 / 792 = 1.82 → 2 rolls.
Tips & Best Practices
- Always overlap horizontal seams shingle-style: upper sheet over lower sheet, so water runs over (not behind) the seam.
- Use the manufacturer's recommended tape at all seams, around windows, and at penetrations.
- Install house wrap from bottom to top (like shingles) for proper water shedding.
- Don't leave house wrap exposed for more than 60–90 days (120 days max for Tyvek) before covering with siding.
- Flash all window and door openings with self-adhering flashing tape before installing house wrap.
- Install cap nails every 12–18 inches to secure the house wrap; staples alone can tear.
House Wrap vs. Building Paper
Traditional building paper (#15 asphalt felt) was the original weather barrier. Modern house wraps offer advantages: lighter weight, better tear resistance, higher moisture vapor transmission, and faster installation (wider rolls mean fewer seams). However, some builders still prefer felt for its self-sealing properties around fastener holes.
Proper Installation Sequence
Install house wrap after sheathing and before window/door flashing. Starting at the bottom, wrap horizontally around the house with each course overlapping the one below. At corners, continue the wrap around (don't terminate at corners). Tape all seams with manufacturer-specified tape. Then flash all openings, and finally install the siding.
ZIP System Alternative
ZIP System sheathing eliminates separate house wrap by integrating a moisture barrier directly into the OSB sheathing panel surface. Seams are sealed with ZIP System tape. This reduces labor (one less trade step) and eliminates the gap between sheathing and house wrap where wind-driven rain can enter. The trade-off is higher sheathing cost.
Sources & Methodology
Last updated:
Frequently Asked Questions
House wrap is installed over the entire wall including across window and door openings. After wrapping, you cut an X or I-shaped slit at each opening, fold the flaps inward, and flash the opening with self-adhering tape. This creates a continuous drainage plane around every opening.
Tyvek HomeWrap (DuPont) is a spunbonded polyethylene sheet with very high moisture vapor transmission. Typar (Berry Global) is a woven polypropylene that is more tear-resistant but slightly less vapor-permeable. Both meet code requirements. Tyvek is more widely specified by builders.
Minimum 6" horizontal overlap (bottom course under top course). Minimum 6" vertical overlap. Many builders use 12" horizontal overlap for better performance. At corners, wrap continuously around the corner by at least 12 inches.
For exterior foam board insulation: house wrap typically goes over the sheathing and under the foam, but some systems place it over the foam. Follow the specific product system's instructions. ZIP System eliminates separate house wrap by integrating the WRB into the sheathing panel.
No. House wrap is designed for vertical wall applications only. It does not have the water-holding capacity needed for roof applications. Use proper roofing underlayment (felt or synthetic) on the roof deck.
The IRC (International Residential Code) requires a weather-resistant barrier behind all exterior cladding. House wrap is the most common way to meet this requirement. Alternatives include building paper (#15 or #30 felt), fluid-applied barriers, and integrated sheathing systems like ZIP.
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