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Ice Dams - Removing

Written by University of Minnesota Extension faculty

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:

• Remove snow from the roof. A "roof rake" and a push broom can be used to remove snow. Performing this work can be very dangerous. It's best to have professionals do this job.
• In an emergency situation to stop water from continuing to flow into the house structure, make channels through the ice dam. Hosing with warm water will do this job. Work from the lower edge of the dam up. The channel becomes ineffective within days, however, and is only a temporary solution.
• The ice dam can be removed from the house but this places the roof and the remover at tremendous risk. This also should be done by professionals.

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