Ice and Water Shield

A self-adhering rubberized asphalt membrane installed on the roof deck in areas vulnerable to ice dams, wind-driven rain, and water backup, providing a waterproof barrier that seals around nail penetrations.

Specifications

Material	Rubberized asphalt with polyethylene film backing
Thickness	Approximately 40 to 65 mils
Width	36 inches standard
Application Temperature	Minimum 40 degrees Fahrenheit for proper adhesion
Code Requirement	IRC R905.1.2: required at eaves where avg. January temp is 25F or below

Common issues

Installed in temperatures below the minimum adhesion threshold, resulting in poor bonding to the deck
Insufficient coverage at the eave, not extending at least 24 inches past the interior wall line as code requires
Wrinkles or bubbles from improper application technique that create channels for water to travel
Not installed in valleys, around penetrations, or at roof-to-wall transitions where it is recommended or required by the shingle manufacturer

Insurance relevance

Ice and water shield is a critical factor in ice dam claims. In regions where it is code-required, its presence or absence determines whether interior water damage from ice dams is attributed to a covered weather event or a construction deficiency. When a roof is replaced after a storm, ice and water shield must be installed per current code even if the original roof did not have it. This is a code-upgrade item that is included in the replacement scope.

What Is Ice and Water Shield

Ice and water shield is a self-adhering roofing membrane made from rubberized asphalt laminated to a polyethylene film. It sticks directly to the roof deck without fasteners and creates a waterproof barrier that seals around nail penetrations. The product was developed specifically to address ice dam leaks at roof eaves, but its waterproofing properties have made it a standard component at valleys, penetrations, and other vulnerable areas on residential roofs. The name "Ice and Water Shield" is technically a brand name (Grace Ice and Water Shield was the original product), but it has become a generic term in the roofing industry for any self-adhering roofing membrane. Equivalent products from other manufacturers include GAF StormGuard, CertainTeed WinterGuard, and Owens Corning WeatherLock.

Where Code Requires It

The IRC Section R905.1.2 requires a self-adhering polymer-modified bitumen sheet (ice and water shield) at the eave of shingle roofs in areas where the average daily temperature in January is 25 degrees Fahrenheit or below. The membrane must start at the eave edge and extend to a point at least 24 inches past the interior face of the exterior wall. On roofs with a 4:12 slope or less, the membrane should extend 36 inches past the interior wall line. Many shingle manufacturers extend the requirement to valleys, roof-to-wall intersections, dormers, skylights, and pipe penetrations for their warranty to be valid. Local building codes in some cold-climate states mandate more extensive coverage than the IRC minimum.

Installation Requirements

Ice and water shield must be applied to a clean, dry, smooth deck surface. The ambient temperature should be at least 40 degrees Fahrenheit for the adhesive to bond properly. The release liner is peeled away as the roll is unrolled across the deck. The membrane is pressed firmly against the deck surface, and a roller is used to ensure full contact and eliminate air bubbles. Overlaps between adjacent sheets should be at least 3 inches at side laps and 6 inches at end laps. The membrane must be lapped over the drip edge at the eave so water running down the membrane surface sheds over the drip edge and into the gutter. At valleys, the membrane is centered in the valley and extends at least 18 inches up each slope from the centerline.

Insurance and Claim Implications

In cold-climate regions, ice and water shield is a determining factor in ice dam claims. If a home suffers interior water damage from an ice dam and the roof has properly installed ice and water shield at the eave, the membrane should have prevented the leak. If the damage occurred anyway, the membrane may have been improperly installed, insufficient in coverage, or the ice dam extended beyond the protected zone. If the roof was built without ice and water shield where code required it, the insurer may deny the claim as a construction deficiency. When a damaged roof is replaced, current code requires ice and water shield even if the original roof did not have it. This code-upgrade cost is part of the replacement scope and should be included in the Xactimate estimate as a separate line item with the square footage specified.

Frequently asked questions

The IRC requires self-adhering membrane at eaves in areas where the average daily temperature in January is 25 degrees Fahrenheit or below. The membrane must extend from the eave edge to a point at least 24 inches past the interior wall line. Many shingle manufacturers also require it in valleys, at roof-to-wall intersections, and around skylights and other penetrations for warranty coverage. Some local codes expand the requirements beyond the IRC minimum.

Technically it can be applied to the entire deck, and some homeowners in extreme climates choose this approach. However, self-adhering membrane is a vapor barrier, and full-deck coverage can trap moisture in the roof assembly if the attic ventilation is inadequate. In most cases, the best practice is to use ice and water shield in the code-required and manufacturer-recommended zones and synthetic underlayment across the remainder of the deck, which allows some vapor permeability.

Ice dams form when heat escaping through the roof melts snow, which refreezes at the colder eave. Water pools behind the ice ridge and backs up under the shingles. Shingles alone cannot stop this backed-up water because it enters through every nail hole and seam. Ice and water shield is self-sealing, meaning when a nail punctures the membrane, the rubberized asphalt squeezes around the nail shaft and maintains the waterproof seal. This is what prevents backed-up water from reaching the deck even though the shingles above have been compromised.

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