Ice dams are common in areas that receive heavy snow buildups. In most cases, ice dams begin inside the house when heated air leaks up into the unheated attic. This phenomenon creates warm areas on the roof, causing the snow on its exterior to thaw. The melting snow moves down the roof slope until it reaches the cold overhang, where it refreezes. The process continues, causing ice to build up along the eaves and form a dam. Eventually, this dam forces the water to back up under the shingles and sometimes into the ceiling or wall inside the home. Ice dams may cause structural framing members to decay, metal fasteners to corrode, and mold to form in the attic and the wall surfaces. Few homeowners insurance policies pay for ice dam removal. The special perils HO form (HO 5), however, typically covers interior or exterior damage arising from ice dams.