Ice Dams: Why They Form and What to Do About Them

Ice dams are thick ridges of solid ice that build up along the eaves" according to homeowners website ThisOldHouse.com. Ice dams form because heat in the attic warms the roof but not the eaves. As the snow on the roof of a house melts, it runs down the roof where it hits the colder roof section above the eaves and freezes.

Through one or more thaw-and-freeze cycles, the ice thickens in the gutter and backs up onto the roof. Then, additional snow melt on the warm roof gets caught under the shingles and seeps through the roof. The water drips inside the roof into the attic and down the interior walls of the house.

The water damage that results from ice dams can be significant to roof, shingles and gutters and to attic insulation, contents and interior walls./

Any significant snow accumulation on the roof can put a home at risk for ice dams. Real estate website HouseLogic points out: “The more snow, the larger the heat loss [into the attic from the house], and the longer the subfreezing temperatures remain, the higher the likelihood that ice dams will materialize.”

To reduce the risk of ice dams, here are prevention tips from ThisOldHouse.com:

• Use heated cables on the roof above the eaves and along the gutters and downspouts. Typically installed before the winter season in regions with significant snowfall, these can keep the snow melt from freezing.
• Use a “roof rake” – a long-handled upside-down scoop – during or after a snowfall to pull snow off the roof above the eaves.
• Over the long term, homeowners might need to have a contractor check the insulation of the attic and address any heat loss from the house into the attic.

According to ThisOldHouse.com, there are three potential remedies homeowners can take if ice dams form:

• Use a roof rake to pull snow off the roof above the eaves.
• Deice the roof by placing ice melt crystals (such as calcium chloride, bundled up in nylon stockings or panty hose) perpendicular to the gutter and hanging over the gutter.
• Blow cold air into the attic with an attic fan or box fan.

Homeowners might be tempted to use a ladder to reach or climb on the roof, then pull off snow or chip away at ice. But doing so can be risky given the snow and ice conditions on the ground and roof and in the gutters. And chipping away at ice can damage the gutters or shingles.

At Selective, homeowners policies typically cover damage to an insured’s dwelling that resulted from ice dams (under the coverage for “weight of ice and snow”). Homeowners coverage for the contents of the house (including items stored in the attic) damaged by either the weight of ice and snow or the resulting melting and leaking is available through Selective homeowners policies.