What is a Ice Dam?

Full definition

An ice dam is a ridge of ice that forms along the cold edge of a roof, typically in or just above the gutter. It forms when warm air leaking from a heated attic melts roof snow, the meltwater trickles down toward the cold roof edge (the overhang past the heated wall), and refreezes there.

Ice dams can back water up under shingles into the attic, damaging insulation, ceilings, and walls. The root cause is attic heat loss; the symptom shows up at the gutter. More on KC ice dams.

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