A winter problem common in Canadian homes: heat leaking into a poorly air-sealed, under-insulated attic warms the upper roof and melts the snow on it; that meltwater runs down to the cold eaves and overhang and re-freezes into a ridge of ice. Water then pools behind the dam and backs up under the shingles, where it can leak into the walls and ceilings below.
$1,500 to $4,800 attic air-seal + insulation top-up (rebates often help)Address soonRoofingInsulation
The quick answer
Ice dams, thick ice and big icicles at the eaves, are a symptom: heat leaking into the attic melts snow that refreezes at the cold edge and backs up under the shingles into your ceilings. Heat cables just hide it; the real fix is air-sealing and insulating the attic, usually $1,500 to $4,800. Ask whether the top-floor ceilings have ever leaked in winter.
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Free. No account. Educational and impartial, not a home inspection.
Why it matters
Ice dams cause recurring roof leaks, stained ceilings, soaked insulation, and rot, but the ice is the symptom. CMHC and Natural Resources Canada are clear that the root cause is heat and air leaking into the attic, so the real fix is air-sealing and insulating the attic floor first, with good attic ventilation as the second line of defence to keep the attic cold and dry. Treating only the ice (e.g. heat cables) means it's back next winter.
How to spot it
Thick ice ridges and large icicles at the eaves in winter; thin, patchy, or unevenly-distributed attic insulation; water stains on top-floor ceilings near exterior walls; and a roof where the snow melts unevenly (bare patches over warm, leaky spots).
What it costs
In the GTA, blown-in top-ups with air-sealing run about $1.20 to $3.00 per square foot, typically $1,500 to $4,800 for a full attic, before rebates (Enbridge HER+ pays up to ~$1,800 when the attic reaches R-60). That excludes repairing water damage the ice dams already caused.
What to do
Address soon in cold climates. Prioritize air-sealing + insulation (the cure) over heat cables (a band-aid), and ask the seller whether top-floor ceilings have ever leaked in winter.
Education and triage, not a home inspection. Casaroo flags ice-dam risk from attic-insulation and eave photos, an insulation or roofing professional confirms the fix.
Common questions
Do heat cables fix ice dams?
They manage the symptom, and the ice comes back next winter. CMHC and Natural Resources Canada are clear that the cause is heat and air leaking into the attic, so air-sealing and insulating the attic floor is the actual fix, at $1,500 to $4,800 for a typical attic.
Is ice damming a roof problem or an attic problem?
Almost always an attic problem wearing a roof costume. Replacing shingles without fixing the attic gives you a new roof with the same ice dams, so ask about insulation and air sealing before you ask about shingles.
What should I ask the seller?
Whether the top-floor ceilings have ever leaked or stained in winter. It is a specific question, it is hard to answer vaguely, and the answer tells you whether the dams have already been getting water inside.
Does insurance cover ice dam damage?
It varies by policy and by whether the damage is treated as sudden or as long-term maintenance neglect. That is a conversation for your broker, and it is a good argument for fixing the attic rather than waiting to find out.
A licensed insulation/roofing pro confirms; Casaroo flags, it does not inspect.
Last reviewed 2026-07-10.
This guide is general education, not a home inspection and not advice for your specific property. Always
consult the appropriate licensed professional, and get a licensed home inspection before you remove conditions
or buy. Cost ranges are 2026 estimates that vary by region, size, and access; confirm specifics with a
qualified professional.