What Is an Ice Dam?

An ice dam is caused when ice forms on the unheated sections of the roof. The roof overhang does not get the heat that comes from inside the home. That heat coming from inside the house melts the snow and ice. When the melting snow and ice hits the unheated space, it refreezes causing an ice dam. Just as the name suggests, it becomes a dam. Any water flowing down the roof will now be backed up behind the dam. Naturally water flows down the slope of the roof. When the water hits the ice dam, water will back up under the roof shingles which can cause the roof to leak.

Ice Dam Diagram

The coastal region of Washington state will be less likely of experiencing ice dams than the rest of the state. However, one ice dam that causes a roof leak can be one too many. in general, homes that are built in a climate that experiences freezing temperatures can expect to see ice dams form. Fortunately, there is a solution to protect the home from leaking if an ice dam forms. Installing a self-adhering ice and water membrane in the unheated sections of the home can prevent these leaks.

Self-adhering ice and water membrane acts like a gasket under the roofing shingles. The membrane seals around the nails and roof penetrations. When applied under the roof shingles in the unheated sections of the roof, it will keep ice dams from causing roof leaks. Installing ice and water membrane in the valley sections and all roof penetrations can prevent leaks that are not caused by ice dams.

Illustration of ice & water membrane locations

Most reputable asphalt shingle manufacturers offer an upgraded warranty protection plan. In order to qualify for the upgraded warranty, the manufactures require the installation of the ice and water membrane. Ask your roofing contractor to include ice dam protection when installing your asphalt shingle roof.