An ice dam forms when snow melts higher on a roof and refreezes near the colder roof edge. Once the ice builds up, water can collect behind it instead of draining into the gutter. Heat loss from the home is a common cause, but unusual freeze-thaw weather patterns can also create ice-dam conditions.
Why It Matters
Backed-up water may work under shingles and reach the roof deck or interior of the home. Ice dams are often connected to heat loss, attic ventilation, insulation gaps, and winter weather patterns. Proper attic insulation and air sealing are usually the best long-term defense because they help keep the roof deck temperature more consistent.
Common Problems
Homeowners may notice icicles, ice buildup at gutters, stained ceilings, or leaks near exterior walls. Removing visible ice may help temporarily, but the cause usually involves the full roof and attic system. In some winters, repeated melting during the day and refreezing at night can create problems even on homes that do not usually experience major ice dams.
Exterior Echelon Notes
Exterior Echelon evaluates ice-dam risk by looking at roof edges, intake and exhaust ventilation, insulation patterns, underlayment protection, and signs of past winter water intrusion. Roofing details matter, but attic insulation and air sealing are often the most important parts of preventing repeat ice-dam problems.
