Ice and water shield is a self-adhering membrane that provides an extra layer of waterproof protection in the areas of your roof most vulnerable to water intrusion. It is required by code in Utah and it is one of the most important components for our climate specifically.

BHR crew installing Grace Ice and Water Shield on a residential roof replacement, Salt Lake City, Utah . Bob Harvey Roofing

How it differs from underlayment

Standard synthetic underlayment is water-resistant, meaning it sheds water that flows over it. But it is not waterproof. If water pools on it or is pushed under it by pressure, it can get through.

Ice and water shield is fully waterproof. It is a rubberized asphalt membrane with an adhesive backing that bonds directly to the roof decking. When a roofing nail penetrates it, the rubberized material self-seals around the nail shaft, maintaining the waterproof barrier. Standard underlayment does not do this.

Where it goes

Eaves. Code requires ice and water shield along the eaves, extending at least 24 inches past the interior wall line. This is specifically to protect against ice dams. When an ice dam pushes water back under the shingles, the ice and water shield at the eaves prevents that water from reaching the decking and getting into the home.

Valleys. Roof valleys channel a lot of water and are high-risk areas for leaks. Ice and water shield runs the full length of every valley, extending at least 18 inches on each side of the valley centerline.

Around penetrations. Pipe boots, vents, and any other roof penetrations should have ice and water shield around them as additional protection beyond the flashing and sealant.

At wall transitions. Where the roof meets a vertical wall, ice and water shield provides backup protection behind the step flashing.

Low-slope areas. Any section of the roof with a pitch below 4/12 should have ice and water shield across the entire area, because low-slope sections are more vulnerable to water pooling and wind-driven rain getting underneath.

"Ice dams are a fact of life along the Wasatch Front. The homes that have proper ice and water shield at the eaves almost always avoid the interior damage."

Why it matters in Utah

Ice dams form every winter along the Wasatch Front. Warm attic air melts snow on the upper roof. That water runs down and refreezes at the colder eaves. The resulting ice dam pushes water back up under the shingles. Without ice and water shield, that water goes straight into the decking. We see ice dam damage every spring, and the homes that have proper ice and water shield at the eaves almost always avoid the interior damage.

What to look for on your estimate

Your roofing estimate should specifically call out ice and water shield and where it is being installed. If the estimate says "underlayment" without distinguishing between standard underlayment and ice and water shield, clarify. They are not the same product and they serve different purposes.