House Wrap Rolls Calculator

Project preset:

Measurement basis:

House length:

House width:

Exterior wall run:

Wrap height:

Known gross wrap area:

Gables and extra wall area:

Roll size:

Custom roll width:

Custom roll length:

Exterior doors:

doors

Windows:

windows

Overlap/cut allowance:{{ waste_percent }}%

Seam taping:

Horizontal lap:

Fastener spacing:

Fastening-line spacing:

{{ field.label }}:

Tape waste allowance:

Fasteners per box:

per box

Expected exposed days:

days

Optional USD prices add a material-only subtotal. Zero leaves quantities, checks, and allowance scenarios unchanged.

House wrap roll price:

$/ roll

Seam tape roll price:

$/ roll

Flashing tape roll price:

$/ roll

Fastener box price:

$/ box

House wrap material takeoff with quantities, optional cost, and estimating basis.
Material	Order	Optional cost	Basis	Copy
{{ row.material }}	{{ row.order }}	{{ row.cost > 0 ? formatCurrency(row.cost) : 'Not priced' }}	{{ row.basis }}

L Lean allowance · P Current plan · R Robust allowance

A house wrap order has to cover more than the flat rectangles on a sketch. Corners consume material, upper courses overlap lower courses, rough openings need flashing, and a nearly complete wall can still require another whole roll. The useful quantity is therefore a takeoff: a linked estimate of wrap, seam tape, flashing tape, and fasteners based on the same wall geometry.

House wrap is one kind of water-resistive barrier installed behind exterior cladding. Its job is to help drain water that passes the cladding while the wall assembly manages air and water at joints, penetrations, and openings. It is not interchangeable with an interior vapor retarder, and a roll count says nothing by itself about whether the completed assembly meets code or the product instructions.

Three measurements commonly anchor a takeoff. A simple rectangular building can start with perimeter and wall height. An irregular shell is better measured as the total exterior wall run. Drawings or a detailed field takeoff may already provide gross wrap area, but wall run and height are still needed to estimate courses, seams, and fastener positions.

House wrap quantities and the measurements that control them
Quantity	Main driver	Common mistake
Wrap rolls	Gross wall area, extra wall area, allowance, and printed roll area	Subtracting doors and windows even though offcuts and flashing details still consume material
Seam tape	Wall run, roll width and length, course overlap, and selected seam policy	Estimating tape from wall area alone
Opening flashing tape	Door and window perimeter	Using opening area instead of perimeter
Cap fasteners	Wall run, wall height, and both spacing directions	Assuming one spacing value covers the whole fastening pattern

House wrap courses, lap, rough opening cut, and roll coverage relationship — Area controls the roll order; wall geometry controls courses, seams, and fastener positions.

Whole-roll rounding can dominate the answer on small jobs. A larger allowance may leave the count unchanged when the order already has ample spare coverage, then cause a full-roll jump at the next boundary. Check the spare area and the allowance comparison rather than treating the allowance percentage as a direct percentage increase in purchased rolls.

How to Use This Tool:

Begin with the measurement path that matches the information you actually have, then replace any preset values with site and product measurements.

Choose House length and width for a simple rectangular footprint, Measured exterior wall run for an irregular shell, or Known gross wrap area when a takeoff already supplies the coverage area.
Enter the Wrap height, gables or other extra wall area, and the printed Roll size. In known-area mode, keep the wall run and height accurate because they still determine seams and fasteners.
Set the overlap and cutting allowance, seam-taping policy, horizontal lap, fastener spacing, and fastening-line spacing from the intended product and wall detail.
Enter door and window counts with representative opening sizes. These values calculate flashing-tape perimeter and flag unusually opening-heavy walls; they do not reduce gross wrap coverage.
Review Wrap material takeoff first, then read Installation checks for low allowance, tight spare coverage, seam-policy, exposure, or opening-density warnings.

Interpreting Results:

House wrap is the purchase count after allowance and whole-roll rounding. Spare area is what remains after that rounding; it is not proof that the roll dimensions suit every wall course or cut.

Use Allowance impact to see whether a leaner or larger allowance crosses a whole-roll boundary.
Compare seam and flashing tape as separate quantities. Seam tape follows course geometry; flashing tape follows opening perimeter.
Treat fastener and exposure warnings as prompts to check the selected product instructions, wall substrate, weather, and local requirements.
If the wall has many returns, balconies, penetrations, or irregular gables, verify the modeled gross area against drawings or a face-by-face field takeoff.

Technical Details:

The takeoff uses feet and square feet internally. Metres, centimetres, inches, and square metres are converted before geometry is calculated. Results keep full precision through the model; displayed values may be rounded, while purchase quantities are deliberately rounded up to whole rolls, tape rolls, and fastener boxes.

Formula Core:

Adjusted coverage is gross wall area plus the chosen allowance, and the roll order is the ceiling of adjusted coverage divided by printed roll area.

\begin{array}{l} A_{gross} = L_{wall} \times H + A_{extra} \\ A_{adjusted} = A_{gross} \times (1 + \frac{w}{100}) \\ N = ⌈ \frac{A_{adjusted}}{W_{roll} \times L_{roll}} ⌉ \end{array}

For footprint mode, wall run is twice the sum of house length and width. Known-area mode replaces the area equation with the entered gross area, but the entered wall run and height remain active for installation geometry.

Secondary house wrap calculation rules
Result	Rule
Courses	One course when wall height is no greater than roll width; otherwise one plus the ceiling of remaining height divided by roll width minus lap. Effective course lift never falls below 0.5 ft.
Vertical seam length	At least one seam segment per course, using the ceiling of wall run divided by roll length, multiplied by course count and roll width.
Horizontal lap length	Wall run multiplied by one fewer than the course count.
Flashing tape	Total rectangular opening perimeter multiplied by one plus the tape allowance. Door and window counts are rounded to whole openings.
Cap fasteners	Whole fastening lines across the wall run, including the end line, multiplied by whole positions up the wall height, including the end position.

Seam tape is zero when No seam tape is selected. Vertical seams only excludes horizontal laps, while All seams includes both. Tape lengths receive their own allowance before division by the entered tape-roll length.

Rule Core:

House wrap warning rules
Condition	Review
Allowance below 8%	Check cuts, corners, damage, and field uncertainty.
Spare area below 5% of one roll	The order is close to a whole-roll boundary.
More than one course without all-seam taping	Confirm the horizontal-lap treatment required by the chosen assembly.
Expected exposure above 90 days	Verify the product's published exposure limit and construction schedule.
Opening area above 35% of gross wall area	Recheck representative opening sizes and the wall-area takeoff.

The allowance comparison evaluates the entered percentage, 4 percentage points less with a floor of 0%, and 8 percentage points more with a ceiling of 35%. Each scenario repeats whole-roll rounding, so its count may stay flat even when adjusted and spare areas change.

Limitations and Accuracy:

Wall geometry and printed package dimensions can support a purchasing estimate, but they do not design the water-resistive barrier. Product-specific laps, compatible tapes, flashing sequences, fastening schedules, wind exposure, substrate, cladding, drainage space, ultraviolet exposure limits, and local code can change both quantity and installation.

The model keeps openings inside gross wrap area and uses their perimeter only for flashing tape.
One representative door size and one representative window size are applied to their respective counts.
Irregular cuts and reuse of offcuts are represented only by the allowance, not by sheet nesting.
Prices are optional arithmetic totals and exclude tax, delivery, labor, and product-specific accessories.

Worked Examples:

Single-story metric footprint

A 12.8 m by 8.5 m footprint with 2.74 m walls and 16.7 m² of extra wall area produces about 1,436.16 ft² of gross coverage. With a 12% allowance and 9 ft × 150 ft rolls, adjusted coverage is about 1,608.50 ft², so the order rounds up from 1.19 to 2 rolls. Those rolls provide 2,700 ft², leaving about 1,091.50 ft² after the modeled allowance. The large spare amount is a consequence of roll size and whole-roll rounding, not a recommendation to reduce product-required laps.

References:

2021 International Residential Code, Chapter 7 Wall Covering, International Code Council, 2021.
Vapor Barriers or Vapor Retarders, U.S. Department of Energy.

House Wrap Rolls Calculator

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Introduction:

How to Use This Tool:

Interpreting Results:

Technical Details:

Formula Core:

Rule Core:

Limitations and Accuracy:

Worked Examples:

Single-story metric footprint

References: