Ice Dam

An ice dam is defined as a ridge of ice that forms along the eave of a roof when melted snow refreezes at the roof edge, preventing proper drainage and causing water to back up under the shingles. Ice dams occur when the upper roof surface is above 32 degrees F while the eave overhang is below freezing, typically caused by inadequate attic insulation and ventilation. Ice dams can cause significant interior water damage and are prevented by maintaining proper attic ventilation, adequate R-value insulation, and installing ice and water shield membrane along the eaves.