Fixing ice dams: the order that actually works
Most fixes target the ice. The one that lasts targets the heat escaping into your attic.
Fixing ice dams starts in the attic, not on the roof. The ice is the result. The cause is warm air leaking from the house, heating the roof deck and melting snow that then refreezes at the cold eave. Fix the leak of heat and the dam has nothing to grow from.
Step one: find where the heat gets in
Stay on the hatch frame or a solid board you trust, and never step between the joists. With a flashlight, look for dark, dirty insulation near the ceiling, which marks where warm air has been pushing through. Common sources are the hatch, recessed lights, bath fan housings, chimney chases and the tops of interior walls. Our page on attic air sealing goes through these one by one.
Step two: seal first, insulate second
Adding insulation on top of open gaps is the classic wasted job. Warm air still rises straight through. Seal the gaps, then bring the insulation to an even depth across the whole ceiling, including the edge over the wall plate. If you are not sure what you have, see what attic insulation is and how it should look.
Step three: let the roof breathe
Air should come in low at the soffit and leave high near the ridge. Check that insulation is not stuffed against the eave and blocking the intake. The basics are in our attic ventilation guide. Ventilation clears leftover heat. It will not rescue a leaky ceiling.
What to do while the ice is already there
You can only work from the ground. A roof rake with a long handle can pull snow off the lowest few feet of the roof, which reduces the water that feeds the dam. Do not use it from a ladder on an icy edge. Do not chip, pick or pour hot water on the ice. Our guide to ice dam removal explains why, and what a professional steamer does differently.
Skip the fixes that treat the ice
Rock salt, calcium chloride socks and heated cables all manage the symptom. Some help in one known trouble spot. None of them stops the melting, and the first two mean going up on the roof. Treat them as a patch, not a plan.
Who does what
Air sealing and insulation belong to an insulation or weatherization contractor, ideally one who tests with a blower door or infrared camera. Ask what they will seal and how they will prove it worked. A roofer is the right call for lifted or cracked shingles. A licensed structural engineer is the call if the ceiling or roof line sags.
Plan the work for late summer or early fall. The best time to fix an ice dam is when there is no ice.
Frequently asked questions
What is the best way to fix ice dams?
Seal the air leaks into the attic, make the insulation continuous and keep the roof ventilated. That keeps the deck cold so snow does not melt and refreeze at the eave.
Can I fix an ice dam myself?
You can do safe ground-level steps and look at the attic from the hatch. Sealing and insulation are best left to a contractor, and nobody should climb an icy roof.
Do heated cables fix ice dams?
They melt a channel for water to escape in one spot, but they do not stop the melting. They are a patch, not a fix.
When should I fix an ice dam problem?
Before the first heavy snow. Attic work is easier and safer when the roof is bare.
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