Winter guide · Ontario

Ice dams, snow load, and snow guards in Ontario

Ice dams start in the attic, not on the panel. Warm air leaks up, melts snow on the deck, and that water freezes at a cold eave. Steel can shed the pack and it does not wick like shingle laps. It does not shut off attic heat. We put snow guards where a slide would hit a door, walkway, or valley, we keep the troughs clear for spring melt, and we do not take an axe to the ice.

How a dam forms.

How an ice dam forms — a cross-section of a typical Ontario roof in winter.

An ice dam is a ridge of ice at the eave. It starts when warm air leaks from the living space into the attic. That heat warms the roof deck. Snow sitting on a warm deck melts from below. The meltwater runs to the overhang. The overhang sits past the heated walls, so it stays cold. The water freezes there and builds a ridge. Melt then backs up behind that ridge.

That sequence does not start on the panel. Ice dams start in the attic. Air sealing, insulation, and ventilation that keep the deck cold are the lasting work.

Three problems. Do not mash them.

Backup leak

Water that cannot drain at the eave finds a path under the roofing and into the house. Asphalt shingle laps can wick. Steel does not wick the same way, and it sheds water better. That changes the leak path. It does not mean the attic heat is gone.

Sliding snow

On steel, snow slides. A slide that comes off in one sheet is a hazard at a door, a walkway, or a parked car. Snow that slides is a hazard we plan for. That is a separate problem from the backup leak.

Snow load on the structure

The roof still has to carry what sits on it. Shedding can reduce how long a pack stays on the slope. It does not let you ignore the load the structure was built to carry. We do not print a load number for a typical house. That figure belongs to the building, not to a brochure.

What steel changes — and what it does not.

Steel changes the leak path and can shed the pack. It does not shut off attic heat. Ice dams start in the attic. A Heritage Series standing-seam roof sheds the same way. It still does not replace air sealing.

In The Blue Mountains the freeze-thaw is harder, and the same attic-first rule holds. A metal roof does not replace that work.

In Angus, Essa Township, homeowners come to us after a winter of ice and water. See the Wakefield Bridge roof in Angus, Essa.

Snow guards are a safety choice, not a cure.

On a typical house we place guards where a slide would hit a door, a walkway, or a valley. That is a safety choice. It is not a cure for ice at the eaves. Where Ideal Roofing’s manuals call for them, we use Ideal Snow Stop, Ideal Guard, or #211. We keep the troughs clear so spring melt has a path.

We keep a path for melt. We do not take an axe to the ice. Whether gutters stay or get replaced is a site decision. We do not invent that call for a house in Angus.

We are roofers, not the insulation contractor. We will tell you if the attic needs a look. How those details go on a roof is in our installation process.

Winter questions

What homeowners ask after a hard winter.

Does a metal roof stop ice dams?

Not on its own. An ice dam starts when warm air leaks into the attic, warms the deck, and melts the snow sitting on it. That water runs to the cold overhang and freezes. Steel sheds water better than asphalt and does not wick like shingle laps. It does not shut off attic heat. The lasting work is air sealing, insulation, and ventilation that keep the deck cold.

Do metal roofs need snow guards?

On steel, snow slides. On a typical house we place guards where a slide would hit a door, walkway, or valley so a slide does not come off in one sheet. That is a safety choice. It is not a cure for ice at the eaves.

Does a metal roof replace attic work?

No. Ice dams start in the attic. We will tell you if the attic needs a look.

Pages that sit next to this one.

Wakefield Bridge in Angus, EssaGranite Grey steel shingles. What to know after ice dams.Read →Installation processHow snow guards and drop zones go on a roof.Read →Wakefield BridgeThe steel shingle on the Angus roof.Read →Metal roof vs shinglesLifetime cost, not a winter claim.Read →All guidesEvery long-form page in one place.Read →

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