Toronto · Forest fire guide

Fire-resistant roofing, Toronto

A Class A fire-rated roof assembly gives a house or cottage the best protection from embers, and the roof covering itself should be something that does not burn. This guide covers what the ratings mean, how the common roofing materials compare, and the FireSmart steps that matter most in Ontario, from the people who replace Ontario roofs every week.

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Fire rating

Class A Fire Rated Available, as a complete assembly

Two layers of GAF VersaShield® over 12 mm plywood, per ASTM E108.

The metal

Aluminum does not ignite

Embers that land on the roof have nothing to burn.

Embers

Carried up to 2 km ahead of a fire

FireSmart Canada. The roof is the biggest target on the house.

Why it matters in Ontario

Most of the area burned in Ontario each year is in the north, inside the province's fire region, far from the cities. But Ontario's seasons have swung hard in recent years, and the forest runs right up to the cottages, camps and towns of cottage country and the north. As of October 2, 2026, Ontario had recorded 798 wildland fires for the year, against a 10-year average of 695 to the same date.

Ontario forest fire seasons: number of fires and area burned
Year	Wildfires	Area burned	What happened
2023	700+	about 441,000 ha	A heavy season across the north, in the year Canada set a national record for area burned.
2024	480	nearly 90,000 ha	A quiet year by comparison.
2025	643	597,654 ha	April to October. The 10-year average at the time was 712 fires and about 210,000 ha a year.
2026	798 to Oct 2	725,000+ ha by July 21	Fires to date against a 10-year average of 695. One fire north of Thunder Bay passed 3,188 km² (about 318,800 ha), and more than a dozen communities, mostly First Nations, were evacuated.

Sources: National Observer for 2023; Ministry of Natural Resources figures reported by Canadian Press (November 3, 2025) for 2024 and 2025; Government of Ontario fire counts to October 2, 2026, and Canadian Press citing CIFFC for area burned to July 21, 2026. Full list at the end of this page.

Cottage country and northern Ontario

We roof houses and cottages from Muskoka, Gravenhurst and Huntsville to Kawartha Lakes, Peterborough, Ottawa and Almonte. A cottage in the forest has the same weak points as any house in a wildfire (the roof, the gutters, the vents, the deck), with fewer people around to notice a spot fire and often a long road and a lake for a water supply.

The Federation of Ontario Cottagers' Associations puts it plainly: cottage and camp owners are in rural and often remote places, so they have to be somewhat self-reliant. Its FireSmart advice for cottages is to start at the roof, work down the outside walls, then move out through the three zones around the building. In northwestern and northeastern Ontario, report a forest fire to 310-FIRE (3473); in central and southern Ontario, call 911 or your local fire department.

How a house catches fire in a wildfire

Many houses lost to wildfire are never touched by a wall of flame. They catch from embers: burning bark, needles and debris carried by the wind, which FireSmart Canada says can travel up to two kilometres.

Embers settle where debris collects: in gutters and roof valleys, against vents, in gaps at the eaves and on decks. A roof covering that burns, or a roof full of dry needles, gives them fuel. That is why the roof, and everything around its edges, is the first thing to get right.

What Class A, B and C actually mean

Roof fire ratings come from ASTM E108 (also published as UL 790) and its Canadian counterpart, CAN/ULC-S107. The tests expose a roof sample to fire from outside the building: a flame spreading across the surface, burning wood brands dropped on it, and repeated bursts of flame. The rating belongs to the assembly that was tested, meaning the covering, the underlayment and the deck together. Change one layer and the rating may not hold.

Class A

Severe fire exposure

Maximum flame spread: 1.8 m (6 ft)
Burning brand test: One 30 cm (12 in) brand, about 2,000 g
Intermittent flame: 15 cycles

The rating FireSmart Canada says offers the best protection.

Class B

Moderate fire exposure

Maximum flame spread: 2.4 m (8 ft)
Burning brand test: Two 15 cm (6 in) brands, about 500 g each
Intermittent flame: 8 cycles

Better than C, not the choice for a house or cottage in the forest.

Class C

Light fire exposure

Maximum flame spread: 4.0 m (13 ft)
Burning brand test: Twenty 4 cm (1.5 in) brands, about 9 g each
Intermittent flame: 3 cycles

Not recommended where wildfire or nearby structure fires are a risk.

Roofing materials compared for fire

Typical classifications as tested. Any one product can differ, so ask for the product's fire listing and the assembly it was tested on.

Typical fire classification of common roofing materials
Material	Typical fire classification	What to know
Untreated cedar shakes and shingles	Commonly unrated	FireSmart Canada: untreated wood shakes are a dangerous combination of combustible material and crevices where embers and sparks collect.
Fire-retardant-treated cedar	Class B or C; some Class A as a tested assembly	The treatment can weather out over the years. Check the product's listing and age.
Asphalt shingles (fibreglass)	Commonly Class A	Fibreglass-mat shingles are usually Class A. The roof still has to be kept clear of needles and leaves, which can ignite on top of it.
Clay and concrete tile	Commonly Class A	Non-combustible, but heavy, and the gaps under the tile need ember-resistant closures at the eaves and ridge.
Natural slate	Commonly Class A	Non-combustible and heavy; the roof structure has to be built for the weight.
Synthetic and rubber composite	Varies by product	Some products reach Class A only with a specific underlayment. Read the listing, not the brochure.
Interlock® aluminum	Class A Fire Rated Available as a complete assembly	Two layers of GAF VersaShield® over 12 mm (15/32-inch) plywood, per ASTM E108. Aluminum itself does not ignite.

The Interlock® roof, built as a Class A assembly

Interlock® roofs are heavy-gauge aluminum, made in Canada by Interlock Roofing at its plant in Delta, BC, and installed in Ontario by our own company. Class A Fire Rated Available as a complete assembly: two layers of GAF VersaShield® fire-resistant underlayment over 12 mm (15/32-inch) plywood, per ASTM E108. CAN/ULC-S107 is the matching Canadian test standard.

The panels weigh roughly 2 to 3.5 kg per square metre depending on profile, a fraction of tile or slate. Every profile (Slate, Cedar Shingle, Shake, Mediterranean Tile and Standing Seam) needs a minimum 3/12 roof slope.

If your house or cottage backs onto forest, tell us at the estimate. We price the Class A assembly and walk the whole roof edge with you: gutters, vents, eaves and anywhere embers could collect.

Product engineering and test reports are the manufacturer's to explain: interlockroofing.com ↗

Beyond the roof: FireSmart your property

Ontario uses the national FireSmart Canada program, and the Government of Ontario publishes its own FireSmart page for homeowners. Both divide the land around a building into three zones. The closer to the house, the more it matters. Ontario's page also lists metal roofing and asphalt shingles as the roofing to use.

Immediate zone · 0 to 1.5 m

The house and a non-combustible strip around it. Ontario's FireSmart guidance: create a non-combustible zone up to 1.5 metres from your home. This is where embers reach the roof, gutters, vents, decks and anything stored against the walls.

Intermediate zone · 1.5 to 10 m

Reduce shrubs, evergreen trees and dead material within 10 metres of buildings, and move firewood, sheds and fuel away from the house.

Extended zone · 10 to 30 m

Thin and prune trees within 10 to 30 metres of the house, and clear dead material, so a fire coming through the lot drops to the ground.

Roof and roof-edge checklist

Choose a Class A roof assembly. Ask your roofer what the assembly is, not just the panel.
Keep the roof and gutters clear of needles and leaves, and choose non-combustible gutters and gutter guards.
Fit non-combustible vents with 3 mm metal screening, as FireSmart Canada recommends, to keep embers out of the attic.
Close open eaves and the gaps at the ridge and roof edges where embers and debris collect, including every inside corner of the roof.
Enclose the underside of decks and porches, and don't store anything combustible on or under them in fire season.

FireSmart Canada's free FireSmart Home Assessment tool, linked from Ontario's FireSmart page, walks you through your own property. Your local fire department can tell you about fire bans and burn permits where you live.

Fire-resistant roofing: questions, answered

What is the most fire-resistant roofing material?

Non-combustible coverings such as metal, clay or concrete tile and natural slate, installed as a Class A assembly. Under ASTM E108 and CAN/ULC-S107 the fire classification belongs to the whole assembly (covering, underlayment and deck), so the same covering can rate differently on a different build-up. On our roofs, Class A Fire Rated Available as a complete assembly: two layers of GAF VersaShield® over 12 mm plywood.

Is a metal roof fire resistant?

Aluminum does not ignite, so embers landing on it have nothing to burn. The fire rating, though, is for the assembly: Interlock® roofs have Class A Fire Rated Available as a complete assembly, with two layers of GAF VersaShield® over 12 mm (15/32-inch) plywood, per ASTM E108.

What is a Class A fire-rated roof assembly?

A roof assembly that passed the most severe of the three fire tests in ASTM E108 (UL 790) or its Canadian counterpart, CAN/ULC-S107: flame spread of no more than 1.8 m (6 ft), a 30 cm burning brand of about 2,000 g without the deck igniting, and 15 cycles of intermittent flame. Class B and C use smaller brands and allow more spread.

Are asphalt shingles fire resistant?

Most fibreglass asphalt shingles are Class A, as tested, and Ontario's FireSmart page lists them with metal roofing as suitable choices. The weak point in a wildfire is usually what sits on and around them: needles and leaves in valleys and gutters, open vents and gaps at the eaves.

Are cedar shakes a fire risk?

Untreated cedar shakes are commonly unrated, and FireSmart Canada describes untreated wood shakes as a dangerous combination of combustible material and crevices where embers collect. Treated shakes do better, but the treatment can weather out.

Does a metal roof make my house fireproof?

No roof does, and no honest roofer will say so. A Class A assembly and a covering that does not ignite take away the largest ember target on the house. Clear gutters, screened vents, a non-combustible strip around the walls and managed trees do the rest.

Do I need a Class A roof assembly in Ontario?

It depends on the building and where it is, so check with your municipality's building department before you start. Where it isn't required, FireSmart Canada still says a Class A fire-rated roof assembly offers the best protection, and that matters most for homes and cottages in or beside the forest.

Is my cottage at risk from forest fires?

Any building in or beside the forest can be reached by embers, which FireSmart Canada says can travel up to two kilometres. Cottages are often at the end of long roads with limited water and a longer wait for help. Start at the roof, then work down the walls and out through the three FireSmart zones.

Will a fire-resistant roof lower my insurance?

Each insurer sets its own rates and rules, so ask yours directly and get the answer in writing. A new roof with a documented Class A assembly is something you can show your insurer.

Who do I call to report a forest fire in Ontario?

In northwestern and northeastern Ontario, call 310-FIRE (3473). In central and southern Ontario, call 911 or your local fire department.

Can you install the Class A assembly on my house or cottage?

Yes, in Toronto. Tell us at the estimate that you want the Class A assembly priced, and we'll walk the whole roof edge with you: gutters, vents, eaves and anything else embers could reach. Call (416) 620-2174 or book a free consultation.

Sources

Figures are as published by each source on the date noted. Page reviewed October 2026.

Get the Class A assembly priced.

A fixed price in writing after one visit. Interlock Metal Roofing (Ontario) Ltd. · 2800 Argentia Rd #5, Mississauga, ON L5N 8L2