An ice dam forms when heat escaping from the house melts snow on the upper roof, the water runs down to the cold overhang, and refreezes. The ridge of ice that builds up there traps more meltwater behind it, which then works its way back under the shingles and into the house.
Why the gutter gets blamed
The ice is most visible in and around the gutter, so that is what gets attention. But a gutter does not cause an ice dam — it just happens to be sitting where the ice forms. Removing the gutter entirely would not stop the dam.
What actually fixes it, in order
- Attic insulation. Stops heat reaching the roof deck in the first place. This is the real fix and usually the cheapest long-term.
- Attic ventilation. Keeps the deck close to outdoor temperature so snow does not melt unevenly.
- Air sealing. Pot lights, bathroom fans and attic hatches leak warm air straight into the roof space.
- Heat cable. Treats the symptom, not the cause. Legitimate on a north-facing overhang or a problem valley, but it costs money to run every winter and should be the last option, not the first.
Keeping gutters working through winter
Clear them in late autumn so meltwater has somewhere to go. Make sure downspouts discharge well clear of the foundation and are not themselves frozen solid — a gutter draining into a blocked downspout will back up and freeze no matter how clean it is.
Written by the Eavestroughing.ca team. Prices are indicative national ranges for planning, not quotes, and vary by province, roof and access. We connect homeowners with independent local contractors and do not perform work ourselves.