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Roofingaka: ice dam formationaka: ice backup

Ice Dam

In Plain English

A ridge of ice that forms at the roof's edge in winter, trapping water that can back up and leak into the building.

Definition

A ridge of ice that forms at the eave of a sloped roof when heat escaping through the roof melts snow, which then refreezes at the cold overhang. The water backed up behind the ice dam can infiltrate under shingles and cause interior damage. Prevention requires adequate attic insulation, consistent ventilation to keep the roof cold, and ice and water shield membrane installation at the eaves.

Example

After repeated ice dam damage, the homeowner had the attic re-insulated and ice and water shield extended 6 feet up from each eave.

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