Ice dam leak: why it happens and what to do right now
The roof is usually sound. Melt water is backing up under the shingles and finding a way in.
An ice dam leak happens when melt water pools behind a ridge of ice at the eave and seeps under the shingles. The shingles are not worn out. They are built to shed water downhill, not to hold it back. The usual sign is a drip or stain along an exterior wall during a thaw, often after a cold snap with a lot of snow.
How to recognize it
The timing is the clue. An ice dam leak appears when the weather warms up or the sun hits the snow, and it stops when the cold returns. Look for stains or drips on the ceiling near the outside walls, damp insulation at the eave, and frost or dark patches on the rafter ends. From the lawn you may see a thick edge of ice at the eave and long icicles. If the leak shows up in the middle of the house, away from the walls, our find the leak tool can help narrow it down.
What to do right now
Protect the inside first. Move furniture and put a bucket or tray under the drip. If the ceiling is bulging with water, keep clear of it and call a pro, because a ceiling full of water can fail without warning. Keep the lights off if the fixture is wet.
If you have safe attic access, check the insulation near the eave. Stay on the hatch frame or a board you trust. Do not step between the joists.
What not to do
Do not climb up to chip the ice. Do not use a hammer, an axe or a shovel on the dam. Picking at ice damages shingles and puts you on a slick roof. Our guide to ice dam removal explains what is safe from the ground and why most methods are a short patch.
Rock salt is also a bad idea. It stains the roof, damages metal and plants below, and only melts a thin channel.
Why it will come back
The dam is a symptom of heat. Warm air escapes from the house into the attic, the deck warms, snow melts mid-slope and refreezes at the cold eave. Until that heat loss is fixed, the same winter produces the same leak. The long-term answer is air sealing, continuous insulation and balanced ventilation, covered in ice dam prevention.
After the thaw
Once the ice is gone, dry the area. Wet insulation loses its value and can hold damp against the framing, which leads to attic mold. Check the ceiling for a stain that keeps spreading, and see our page on ice dam damage for what each sign means.
When to call a pro
Call a roofer if shingles are lifted or cracked, or if the leak returns after the next storm. An insulation or energy auditor contractor can find the air leaks. Call a licensed structural engineer if the ceiling sags or the roof line looks bowed, and do not put weight on it.
Frequently asked questions
Why is my roof leaking when it is cold?
Usually an ice dam. Melt water backs up behind ice at the eave and seeps under the shingles during a thaw.
Is an ice dam leak a sign the roof is bad?
Not necessarily. The shingles can be sound. The cause is heat leaking from the house into the attic.
What should I do when an ice dam is leaking inside?
Protect the room, catch the water, keep clear of a bulging ceiling, and keep off the roof. Then deal with the cause after the thaw.
Will the leak stop on its own?
It stops when the weather freezes again, but it returns with the next thaw until the heat loss is fixed.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NOAA / National Weather Service. Winter — National Weather Service safety hub
- NOAA / National Weather Service. What To Do If You're Caught in a Winter Storm