Quick answer
Ice dams form when warm air from the house melts snow on the upper roof and the water refreezes at the colder eaves. Prevent them with good attic insulation and air sealing, balanced ventilation (soffit intake and ridge exhaust), and ice & water shield along the eaves when the roof is replaced.
After a snowy stretch you may see thick ridges of ice along the eaves and icicles hanging from the gutters. That’s an ice dam — and the water backing up behind it can leak into walls and ceilings.
Why ice dams form
Heat escaping from living space warms the roof deck, melting snow from underneath. The meltwater runs down to the colder overhang and refreezes, building a dam that traps more water behind it.
Warning signs
- Heavy icicles along the gutters
- Ice ridges at the roof edge
- Water stains on ceilings or exterior walls after snow
How to prevent them
- Insulate and air-seal the attic floor so heat stays in the house
- Balance ventilation with vented soffit intake and ridge exhaust
- Install ice & water shield along eaves and valleys during a roof replacement
- Keep gutters clear so meltwater can drain
If you’ve had leaks from ice dams, call (908) 636-9745 for an inspection.
Frequently Asked Questions
Are ice dams covered by homeowners insurance?
Water damage from ice dams is often covered, but coverage varies by policy. Check with your insurer and document damage with photos.
Should I chip ice dams off my roof?
No. Chipping ice can damage shingles and is dangerous. Carefully remove snow from the lower roof with a roof rake from the ground, and call a professional for severe cases.
Do heated cables stop ice dams?
They can help in problem spots, but they treat the symptom. Fixing insulation and ventilation addresses the cause.