The short answer
An ice dam forms when heat from the house melts snow on the roof and the meltwater refreezes at the cold eaves. Water backs up behind the ice and leaks under the shingles into the attic, ceilings and walls. Stay off the roof, catch the drips, rake snow off the lower roof from the ground if it's safe, and call a roofer for the ice and a restoration company for the wet ceilings and insulation.
On this page
How ice dams form
- Warm air leaks into the attic and heats the roof deck.
- Snow on the upper roof melts, even on cold days.
- Meltwater runs down to the eaves, which hang past the warm walls and stay cold.
- It refreezes there, building a ridge of ice.
- More meltwater pools behind the ridge and works under the shingles.
Why Westfield gets them
At Westfield-Barnes Regional Airport, the average January high is 32.9°F and the average low is 12.9°F (1981–2010 normals). Snow can stay on roofs for weeks, melting on sunny afternoons and refreezing at night, which is exactly the cycle that builds ice dams.
Warning signs
- thick icicles hanging from gutters and eaves
- a ridge of ice along the roof edge
- water stains or peeling paint on top-floor ceilings near exterior walls
- damp spots on exterior walls, or water around window frames upstairs
- wet or matted insulation in the attic
What to do when it leaks
Safety first.
- Stay off icy roofs and ladders.
- Keep clear of sagging ceilings, and turn off power to wet light fixtures at the panel if you can reach it safely.
- Catch drips with buckets and move furniture.
- From the ground, a roof rake can pull snow off the lower few feet of the roof.
- Don't chip at the ice with hammers or shovels, which damages shingles.
Then call a roofer or ice dam removal service, and a restoration company to dry or replace wet ceilings, insulation and walls. The EPA's water damage guidance says wet insulation should be replaced. See ceiling leaks and ice dams.
Preventing ice dams
- Air sealing: stopping warm air from leaking into the attic around light fixtures, chimneys, attic hatches and plumbing vents.
- Insulation: enough attic insulation to keep the roof deck cold.
- Ventilation: soffit and ridge vents that keep the attic close to outdoor temperature.
- Snow removal: raking the lower roof edge after big storms.
Ice dams and insurance
Interior water damage from an ice dam is often covered by homeowners insurance, while the cost of removing the ice and fixing insulation may not be. Photograph the icicles, the roof edge and the interior damage, and read our water damage insurance guide. For local help, see our main page on water damage restoration in Westfield.
Sources
- Westfield, Massachusetts (Wikipedia: 2020 Census population, geography, Westfield-Barnes Regional Airport climate normals, 1981–2010)
- EPA, Mold Remediation in Schools and Commercial Buildings, Chapter 4 (responding to water damage within 24–48 hours)
Frequently asked questions
Are icicles a sign of an ice dam?
Large icicles along the eaves often mean meltwater is refreezing at the roof edge, which is how ice dams form. Check top-floor ceilings and exterior walls for stains.
Should I remove an ice dam myself?
Raking snow from the lower roof edge from the ground can help. Climbing onto an icy roof or chipping at ice is dangerous and can damage the shingles, so call a professional.
Does insurance cover ice dam damage?
Interior damage is often covered, but policies vary, and removing the ice may not be. Document everything and check your policy.