All glossary terms
Roofing
Ice Dam
Definition: An ice dam is a ridge of ice that forms at the edge of a roof, preventing melting snow from draining off. Backed-up water can leak under shingles and into walls and ceilings.
Ice dams are a winter-climate roof's worst enemy. They form when heat escaping the attic melts snow on the upper roof; that water runs down to the colder eave (which sits beyond the heated attic envelope), refreezes, and builds up into a dam of ice along the gutter line. As the cycle repeats, water pools behind the dam — and water always finds a way in.
The damage from an ice dam isn't always obvious. Common signs:
- Water staining on ceilings near exterior walls
- Peeling paint or bubbling drywall above windows
- Mold in attic insulation
- Sagging gutters from ice weight
- Icicles along the roof edge (the visible symptom, not the cause)
The fix is rarely "more ice melt." Real solutions:
**Adequate attic insulation.** Reduces heat escape from the living space into the attic. Most homes built before 2000 are under-insulated by modern standards.
**Balanced ventilation.** Soffit intake + ridge exhaust vents keep the attic close to outdoor temperature, preventing snow melt on the roof above.
**Ice-and-water shield extended into the field.** Code requires it at eaves; quality installers extend it 3-6 feet into the field on north-facing slopes. If the dam still forms, water can't penetrate the underlayment.
For estimators in cold climates: ice-dam prevention is one of the highest-converting topics for homeowner-facing content. "Why your roofer didn't tell you about ice dams" outperforms generic "roof replacement" content for homeowners with previous water damage history.