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Extension > Environment > Housing Technology > Moisture Management >Ice dams - removing

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Ice dams - removing

Timothy Larson, Lewis Hendricks, and Patrick Huelman
Reviewed by Richard Stone, 2014

If you have icicle decorations hanging from your roof, then you probably have ice dams building up. They can cause damage to your house. Ice dams can be prevented by controlling the heat loss from the home.

An ice dam is a ridge of ice developing at the edge of a roof. This prevents melting snow from draining off the roof. The dam grows in size as it is fed by the melting snow above it. The water above backs up behind the ice dam and remains as a liquid. This water finds cracks and openings in the exterior roof covering and flows into your attic space. From the attic it could flow into the home. This may damage exterior walls, insulation and the ceiling finish. It may also lead to the growth of mold and mildew, which could have an adverse impact on your health.

Ice dams are caused by non-uniform roof surface temperatures. This occurs due to heat flowing from the house. The heat can move through the ceiling and insulation. When the snow on a roof's surface is above 32 degrees it melts. This water flows to areas below 32 degrees and freezes. If there are cracks or openings in the ceiling, the warm air from the house will rise into the attic space and heat the roof as well. There is a complex interaction between heat loss, snow cover and outside temperatures, which may or may not lead to ice dams.

How should a homeowner deal with ice dams? For immediate action, you can take the following steps:

Reviewed by Richard Stone; Extension educator, housing technology; 2010

Copyright © 2013 Regents of the University of Minnesota. All rights reserved.

Revised: Richard Stone, 2006
Reviewer: Richard Stone, 2010, 2014

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