Ice dams form when heat escaping into the attic melts snow on the roof, and the meltwater refreezes at the cold edge of the eaves. Eavestroughs do not cause them, but they take the damage: torn hangers, split joints and water behind the fascia. The lasting fix is attic insulation and ventilation; the eavestrough's job is to drain whatever does melt.
How ice dams form
- Heat escapes through the roof from gaps in attic insulation or air sealing.
- That heat warms the upper roof and melts the snow on it.
- Meltwater runs down to the eaves, which overhang the house and stay cold.
- It refreezes at the eave and in the trough, building a ridge of ice.
- Water backs up behind the ridge and can work under the shingles and into the ceiling.
Orillia and Barrie both sit in the lake-effect snowbelt, so roofs there carry a lot of snow for a long time, which is exactly the condition ice dams need.
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What ice dams do to eavestroughs
- Tear hangers and brackets out of the fascia.
- Pull whole runs away from the house.
- Crack or split sectional troughs at the joints.
- Rot the fascia board if water gets behind it.
In bad winters the weight and the backed-up water can damage roof decking and shingles as well.
Why chipping the ice off is not the fix
Removing ice by hand relieves the weight for a while, but the dam reforms with the next thaw. Doing it from a ladder in winter is dangerous, and metal tools easily puncture troughs and shingles.
What reduces the damage
- Attic insulation and ventilation: the real cure, because it stops the melting in the first place.
- Correct pitch: a trough that falls steadily toward the downspout drains before water can sit and freeze.
- Downspouts sized for the roof: undersized downspouts are usually the first place ice forms.
- Closely spaced hangers: they hold the trough on under the weight of ice.
- Heat cable: an option on roofs that dam every year; ask whether the trough and downspouts suit it.
After a damaging winter
If the troughs are sagging, pulling away or split, deal with it before the spring rains. A damaged trough in April puts water straight against the foundation in the wettest weeks of the year. We can pass your request to one independent local exterior contractor covering your town, who can look at the whole system and quote what it needs.
Frequently asked questions
Will new eavestroughs stop ice dams?
No. Ice dams start with heat loss through the roof. Well-installed troughs reduce the damage and drain meltwater, but the dam itself is stopped by insulation and ventilation.
Are heat cables worth it?
On a roof that dams every winter they can keep a channel open for meltwater. They use power and need to be installed to suit the roof and troughs, so treat them as a supplement to fixing the attic, not a replacement for it.
Is ice dam damage covered by home insurance?
It depends on the policy and on what was damaged. Call your insurer before repairs start, and take photos of the damage first.