What is an ice dam?

• A. A decorative feature on a roof.
• B. A condition formed by thawing and refreezing of melted snow, especially at the lower roof edge on the roof overhang and in gutters. Can cause water to pond and flow up and under shingles, causing leaks.
• C. A required metal anchor for gutters.
• D. A type of insulation.

Answer: (B)

An ice dam is a buildup that forms when snow on a roof melts and the water flows down to the colder eaves, where it refreezes. This usually happens at the lower edge of the roof and in gutters, creating a dam that blocks the flow of meltwater. As more water backs up behind the dam, it can pond and be forced up under shingles, leading to leaks into the attic or interior and potential damage to roofing, insulation, and structure.

This isn’t a decorative feature, nor is it a gutter anchor or a type of insulation. It’s a conditions-driven problem that can be mitigated by keeping the attic and roof assemblies well ventilated and properly insulated, sealing air leaks, removing snow from the roof when safe, and using protective measures like ice and water shield at the eaves and keeping gutters clear.