What is Ice and Water Shield?

Stephen Vernon
April 3, 2023

What is Ice and Water Shield, and why is it important?

Ice and water shield is simply a peel-and-stick barrier between your shingles and the roof. It does what the name suggests. It protects or shields the roof decking from ice and water. Multiple layers protect your roof decking, and shingle manufacturers require ice and water shield as one necessary layer to warranty your roof. If the water get’s underneath the surface of the shingles on your roof, the ice and water shield protects the decking from getting wet. Specific placements of ice and water shield would be along the eaves of your roof, in valleys, and penetrations in your roof. This is the second most important aspect of your roof besides your shingles. One specific use of ice and water shield is to protect against ice damming.

Ice Dam Protection

According to Owen’s Corning, “Ice dams are formed by the continual thawing of snow over the warmer portions of the roof and refreezing over the cold eaves.

The ice dams can cause the backup of water and slush under the exposed roofing material and cause damage to the structure.”

Picture this: It snows one night, and the snow fills up your gutter.

Snow starts collecting up the eave of your roof. As that snow melts, it refreezes along your roof's eave, sometimes allowing water to run underneath the shingles.

Ice and water is a waterproof, self-adhesive material that is far more durable than synthetic paper and is created for situations where ice may stay for some time.

This specific membrane is used on ridges, hips, flashings, and valleys. You’ll find it installed around dormers, skylights, and chimneys.

All these areas are known to collect water. Why not install ice and water shield on the entire roof?

This self-adhering membrane is a vapor retarder which means that the material reduces the ability that vapor can move through it.

This brings us to the importance of roof ventilation.

The ridge vent allows the attic's ventilation to release vapors to release moisture from your attic and roof.

With ice and water shield being vapor retarders, it’s important to understand how your roof's ventilation system is set up.

Ventilation should be equal at the soffit and ridge of your home. Owen’s Corning says that if you’re unsure, always provide more than 50% of the required ventilation at the soffit and the remainder at the ridge.

Other types of ventilation would be a box or circle-looking boxes.

Ask your roofing contractor about ventilation if you’re concerned about a lot of ice and water shield installation on your roof.

Cenvar Roofing and Ice and Water Shield

We state in our contracts that “Ice and water shield shall be installed 3 feet from all bottom edges of the roof, in all the valleys, at all pitch changes, in all flashed areas (i.e. where roof hits walls, chimney, etc.) and around all roof penetrations (i.e. skylights etc.)”Follow along with Sean as he installs ice and water shield on this modular roof for training purposes, or learn more about ice and water barriers on Owen’s Corning’s site.

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