Definition
Think of this like a dam made of frozen water that builds up at your roof edge. When snow melts and refreezes in your cold gutters, it backs water up under your shingles and into your home—and it's way more common than you'd think if you live somewhere cold.
Not sure where this fits?
Answer a few questions and we’ll open the path that fits, at the right step.
Find my pathAbout this term
Ice dams form when warm air from the home heats the roof deck, melting snow. The meltwater flows down to the cold gutter area, refreezes, and creates a dam blocking further water flow. Backed-up water infiltrates under shingles, saturating underlayment, decking, and attic insulation. Preventative measures include adequate attic insulation, proper ventilation, sealing air leaks, and heat cables. Inspection for ice dam evidence reveals ventilation and insulation deficiencies.
Pro Tip
If you're in a snowy climate, proper attic insulation is your best defense. It's worth the investment because ice dam damage gets expensive fast—much more than good insulation costs.
Example
A homeowner in Wisconsin experienced ice dam leaks every spring, causing water stains on upstairs ceilings. An energy audit revealed the attic lacked adequate insulation (R-11 instead of R-38) and had multiple air leaks from the living space. Adding insulation and sealing air leaks eliminated the ice dam problem.