Preventing Ice Dams: Why Gutters and Attic Insulation Matter

An ice dam forms when heat escaping from the attic warms the roof enough to melt snow, which then refreezes at the colder eaves and backs up under the shingles. It’s one of the more common sources of winter water damage, and it’s largely preventable.

Clean gutters are the first line of defence, since blocked eavestroughs give melting snow nowhere to go but back up under the roofline. But gutters alone won’t solve the underlying issue if your attic is losing heat unevenly. A roof that’s warm in the middle and cold at the eaves, rather than uniformly cold, is a sign that attic insulation or ventilation needs attention.

Proper attic insulation keeps heat where it belongs, inside the living space, rather than letting it escape upward and melt snow unevenly. Good attic ventilation matters just as much, since it keeps the underside of the roof at a consistent, cold temperature so snow melts evenly, or not at all, rather than in patches.

If ice dams have been a recurring problem, it’s worth having a contractor assess both insulation levels and ventilation together, rather than just adding heat cables to the roofline as a yearly patch. Heat cables can help in the short term, but they’re treating the symptom, not the cause.

This is especially worth checking on an older cottage or a home that’s had insulation added piecemeal over the years, since gaps and inconsistencies are common in older attics.

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