Craft Quantities
Plan & Takeoffs

Solve backwards

How much eave will my rolls of ice and water shield cover?

Ice and water shield is bought by the roll and laid by the foot of eave, one course up the slope from the drip edge. Enter the rolls you have and the length of eave they protect comes back at the calculator's 36 inch (914 mm) course, with its ten per cent uplift for laps taken back off what you own.
  • 2 rollsThe example worked below
  • Ice & Water Shield CalculatorEvery figure is its own

You have

How much ice and water shield?

rolls

Worked by the Ice & Water Shield Calculator at the settings below.

Saved amounts stay in this browser.

The settings it uses

Coverage Width From Eave
36 in

What it will do

364 sq ft of eave strip

33.8 m²

  1. One eave. Enough for 121 ft of eave.

  2. Or several. About 2 eaves of the size the Ice & Water Shield Calculator opens on: 49 ft of eave.

Check it forwards

Total Eave Length
121 ft
It asks for
2 rolls
You have
2 rolls

The Ice & Water Shield Calculator asks for 2 rolls at that size, and 3 rolls one step larger.

Open this in the Ice & Water Shield Calculator

If you had more, or less

Around your amount

Each worked by the Ice & Water Shield Calculator at the same settings.

  1. Half

    1 roll

    182 sq ft

    60.6 ft of eave

  2. Yours

    2 rolls

    364 sq ft

    121 ft of eave

  3. Half as much again

    3 rolls

    545 sq ft

    182 ft of eave

  4. Double

    4 rolls

    727 sq ft

    242 ft of eave

Common amounts

What each amount of ice and water shield covers

The sizes it is usually sold in, each worked by the Ice & Water Shield Calculator at the settings above.

You haveIt coversAs one eaveAverage eaves
1 roll182 sq ft(16.9 m²)60.6 ft of eave1
2 rolls364 sq ft(33.8 m²)121 ft of eave2
3 rolls545 sq ft(50.7 m²)182 ft of eave3
5 rolls909 sq ft(84.5 m²)303 ft of eave5

Two hundred square feet, sixty feet of eave

The calculator counts a standard self-adhered roll, 36 inches wide, at about 200 square feet (18.6 m²), and adds ten per cent to the strip before dividing. Read backwards, one roll protects about 60.6 feet (18.5 m) of eave in a single course. The uplift is not spare: a side lap of 3 inches (75 mm) leaves a 36 inch roll covering about 33 inches of deck, some 8% of its width gone before any cutting.

When one course is not enough

Many codes want the membrane to reach at least 24 inches (610 mm) inside the exterior wall line, measured up the slope. On a deep overhang or a low pitch that is two roll widths or more, and every extra course halves the eave a roll protects — two courses bring one roll down to about 30.3 feet (9.2 m). Measure from the drip edge to 24 inches past the wall, then divide by the roll's net width to count the courses.

Low slopes want the whole deck

The calculator only ever returns an eave strip. Where a roof falls below its covering's minimum slope — many asphalt shingle systems stop at 2:12 — the usual remedy is membrane or doubled underlayment over the entire deck, and porch roofs, shed extensions and dormer tops are exactly where that comes up. That is a whole-deck area, a different sum from an eave course, and it is worth working out before the rolls are split.

How the answer is worked

Nothing here is a second formula. The Ice & Water Shield Calculator runs forwards — a size in, a quantity out — and this page grows its own starting eave in proportion until the quantity it asks for is what you have. Where it rounds up to whole containers, the answer is the largest size before the next one would be needed.

Where the calculator adds an allowance for cuts or breakage when you order, the same allowance comes off here, because it is the same calculator: a stack you already own finishes less than its face value. Where it adds none, neither does this page — the settings beside the answer say which.

Ice & Water Shield Calculator

runs it forwards

Estimate how many rolls of self-adhered ice & water shield membrane you need for your roof eaves.

Work out what to buy instead

Solve backwards

Other things you might already have

Solve backwards

Start from what is already in the yard

Paint, sheets, rolls, bags and pieces, each read the other way by the calculator that orders it.

Every Solve Backwards pageIce & Water Shield Calculator

  • The calculator's own figures

    Nothing is estimated twice: the page runs the same calculator you would order with.

  • The largest size that fits

    Where a calculator rounds up to whole containers, the answer stops before the next one.

  • Both unit systems

    Gallons and litres, square feet and square metres, side by side.

Frequently asked questions

How much eave strip does 2 rolls of ice and water shield cover?
At the Ice & Water Shield Calculator's own settings, 364 sq ft (33.8 m²) — 121 ft of eave. That is about 2 eaves of the size the calculator opens on: 49 ft of eave. Every figure follows the settings, which you can change in the calculator.
How many feet does a roll of ice and water shield cover?
A standard 36 inch roll of about 200 square feet (18.6 m²) runs roughly 67 feet (20 m) long. Laid as one course along the eave with the calculator's ten per cent for laps, it protects about 60 feet (18.5 m) of eave; two courses up the slope halve that.
How far up the roof does ice and water shield need to go?
Many codes require it to extend at least 24 inches (610 mm) inside the exterior wall line, measured up the slope from the eave. With an overhang that often means two or more roll widths, so the number of courses comes from the overhang and the pitch, not from the roll. Check the code adopted where you build.
Does the whole roof need ice and water shield?
Not on a roof at an ordinary pitch, where it goes along the eaves and at other vulnerable areas the code or the shingle maker names. Below a covering's minimum slope, such as the 2:12 many asphalt shingle systems stop at, membrane or doubled underlayment over the whole deck is the usual remedy — a full-deck area, not an eave strip.