Definition for word: Ice Dam

A ridge of ice that forms along the lower edge of a roof, possibly leading to roof leaks. Ice dams are usually caused by heat leaking from the attic, which melts snow on the upper parts of the roof; the water then refreezes along the colder eaves, forming a dam that allows water to penetrate under shingles, possibly leaking into the attic.

Referrence from

An ice dam (or ice jam) occurs when water builds up behind a blockage of ice. Ice dams can occur in various ways.

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