Ice and Water Shield Calculator

Rolls of membrane for eaves and valleys, with the courses needed to reach 24 in inside the warm wall.

Project Details
Enter your measurements and requirements
$
Results
Calculated estimates for your project
Reach along the slope47.0 in
Courses up from the eave2
Membrane length160 lf (480 sq ft)
Rolls, 200 sq ft3
Estimated cost$285

Turn these numbers into a build plan.

  • 2 courses
  • 3 rolls
  • $285 est. cost
Materials List
Recommended materials and quantities
Ice and water shield, 200 sq ft rolls3

Checked against IRC 2021, section R905.1.2. These rule values have not been reviewed by a licensed professional. Your local code and inspector decide, so verify with your building department.

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Project plan · built from your numbers

Ice and water shield, 80 ft of eave

2 courses along 80 ft of eave plus 0 ft of valley: 3 rolls of membrane.

Materials
$285
Time
1 day
Level
Intermediate
6 steps 5 tools 3 materials
  1. 1

    Check the local requirement

    Ask your building department how far the barrier must reach and whether a permit covers the reroof.

    • Requirement confirmed
  2. 2

    Prepare the deck

    Strip to clean, dry sheathing. Reset nails and replace soft boards.

    • Deck dry
    • Nails flush
  3. 3

    Install eave drip edge

    Fasten drip edge along the eave so the membrane laps over it.

    • Drip edge fastened
01 · Your numbers
Courses
2
Rolls
3
Est. cost
$285
02 · The plan

6 steps · 5 tools · 3 materials

3 more steps, the full tool list and a shopping list you can check off as you go.

03 · Finished

Your plan is 60% built. Save it.

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Ice and water shield, 80 ft of eave

Finished in 1 day · $285 DIY

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How to work out ice and water shield

Rolls are 3 ft wide, so the reach up the slope decides how many courses you run along each eave.

  1. Add up the eaves. Measure every eave that sits over heated space.
  2. Find the reach. Add overhang, wall thickness and 24 in, then multiply by the pitch factor to get the length along the slope.
  3. Count courses. The first course covers 36 in. Each added course covers 33 in after a 3 in head lap.
  4. Add valleys. Run one full-width strip up the center of every valley.
  5. Divide into rolls. Add 10% for end laps and cuts, then divide by the 66.7 ft in a 200 sq ft roll.

Courses and rolls for 100 ft of eave

PitchReachCoursesRolls
3:1243 in24
6:1247 in24
9:1253 in24
12:1259 in24

Figures use a 12 in overhang and a 6 in wall. Size the shingles with the roofing calculator and see the install order in the asphalt shingle guide.

Frequently asked questions

How far up the roof does ice and water shield go?

Where it is required, the model residential code asks for a barrier from the eave to at least 24 in inside the exterior wall line. Local rules vary, so check with your building department.

How much does a roll cover?

Most rolls are 200 sq ft: 3 ft wide by about 66.7 ft long. Some brands sell 100 or 225 sq ft rolls, so check the label.

Do valleys need ice and water shield?

It is standard practice in cold and wet climates. Run one strip centered in the valley before any other underlayment.

Is it needed in warm climates?

The model code only requires an ice barrier where the local jurisdiction has a history of ice damming. Many roofers still use it in valleys and around penetrations.

Does it go on top of the drip edge?

Common practice is drip edge first at the eave with the membrane over it, and drip edge over the membrane at the rakes. Follow the shingle maker's instructions.

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