Ice Barrier Installation

An ice barrier, also called eave protection or an ice and water shield, is a waterproof membrane installed along the lower edge of a pitched roof. Its purpose is to keep out water that backs up behind ice dams, which form when snow melts over a warm roof and refreezes at the colder eaves. Ice barriers are standard in North America and other cold climates; they are uncommon in mild-winter regions.

When it is required

Under the US International Residential Code, an ice barrier is required in areas where ice damming has historically occurred. Each jurisdiction decides where the requirement applies, based on its local history of ice damming. Canadian practice treats eave protection as standard over most of the country.

Materials

Building America guidance lists two acceptable forms:

• at least two layers of underlayment cemented together; or
• a self-adhering polymer-modified bitumen membrane.

Self-adhered membranes are the common modern choice because they seal around nail shanks.

Coverage

The IRC requires the barrier to run from the eave edge to a point at least 24 in (610 mm) inside the exterior wall line of the building. On homes with deep overhangs, this often means two or more courses. Building America guidance adds that on slopes steeper than 8:12, the barrier should extend at least 36 in (914 mm) measured along the slope. Canadian tile guidance specifies eave protection extending at least 1220 mm (48 in) up the slope.

Installation steps

1. Clean the deck and check that it is dry and within the membrane's temperature range.
2. Measure the required coverage from the eave edge to the point inside the wall line.
3. Unroll, position and remove the release film, pressing the sheet down from the centre outward.
4. Lap successive courses and end joints as the manufacturer specifies.
5. Integrate with drip edge, valleys and penetrations.

In Bloomington, Minnesota, the code allows an existing adhered ice barrier to remain and be covered with a new layer during re-roofing. Ice barriers reduce the effects of ice dams but do not prevent them; insulation, air sealing and ventilation address the cause.