Ontario · Roof lifespan guide

How long does a metal roof last in Ontario?

It depends on the metal, the coating, the fasteners and the installation. Steel lasts about as long as its coating keeps it from rusting. Aluminum doesn't rust, and aluminum has been known to last over 100 years. That is a property of the metal, not a promise; what we and the manufacturer promise is in the warranties, set out below.

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The metal

Aluminum has been known to last over 100 years

Aluminum doesn't rust. A property of the metal, not a guarantee.

The material

Guardian Lifetime Limited Material Warranty

Material and finish, for the original purchaser's ownership. Transferable once.

The finish

30 Year Alunar® Coating Warranty

On the paint finish that carries the colour.

What decides how long a metal roof lasts

"Metal roof" covers very different products. Four things decide how long one lasts on your house.

The metal

Steel rusts wherever its protective coating is scratched, cut or worn through, so a steel roof lasts about as long as its coating. Aluminum doesn't rust. It forms a thin oxide layer on its own surface, which is why aluminum has been known to last over 100 years.

The coating

The paint finish decides how the colour holds up to sun and weather. Interlock® roofs carry a 30 Year Alunar® Coating Warranty on the finish, separate from the material warranty.

The fasteners

Exposed screws through the weather surface rely on rubber gaskets that age in sun and cold. Interlock® panels lock to each other on all four sides with the fasteners concealed, so there is no exposed screw head for water or wind to work on.

The installation

Flashing at walls, chimneys, valleys and skylights, the underlayment, the ventilation of the attic below, and the slope (every Interlock profile needs a minimum 3/12) decide how a roof performs for decades. Wind resistance is warranted to 193 km/h (120 mph) installed to manufacturer specification.

What an Ontario winter does to a roof

A roof here works through freeze-thaw, heavy snow, ice and summer heat every year. Each of those finds a different weak point.

Freeze-thaw

Water that gets into a roofing material freezes, expands and thaws, over and over through an Ontario winter. Asphalt granules loosen and wood splits. Aluminum absorbs no water, so there is nothing in the panel for freeze-thaw to work on.

Snow and lake-effect snow

Snowbelts off Georgian Bay, Lake Huron and Lake Ontario can load a roof for weeks. Metal sheds snow; where a slide would land on an entry, a deck or a walkway, snow guards go in. We plan them at the estimate, not after the first slide.

Ice dams

Ice dams come from heat escaping into the attic and from ventilation, not from the roof covering, and no roof prevents them on its own. Ice damming is a stated exclusion of the material warranty. We look at your attic ventilation and insulation with you.

Summer sun and heat

Ultraviolet light and heat dry out asphalt and fade cheap paint. The Alunar® finish is what carries the colour, and its 30-year coating warranty is what to read.

Metal, asphalt and cedar compared

Published life expectancies are averages. Local weather, the building and its design, material quality and maintenance all move them, as the study below says itself.

Typical life expectancy of roofing materials
Roof	Life expectancy	Basis	What to know
Asphalt shingles	About 20 years	NAHB / Bank of America study (2007)	The most common roof in Ontario. When it is done, it comes off or, if suitable, is roofed over once.
Wood shakes	About 30 years	NAHB / Bank of America study (2007)	Needs cleaning and re-treating, and splits and rots as it ages. Always torn off before a new roof.
Interlock® aluminum	Aluminum has been known to last over 100 years	A property of the metal, not a guarantee	The guarantee is in the warranties: the Guardian Lifetime Limited Material Warranty and the 30 Year Alunar® Coating Warranty.

Asphalt and wood shake figures: National Association of Home Builders and Bank of America Home Equity, Study of Life Expectancy of Home Components, February 2007 (a US study). Full reference at the end of this page.

The warranties, stated separately

How long aluminum can last and what is guaranteed in writing are two different things. Here is what is guaranteed on an Interlock® roof installed in Ontario.

Guardian Lifetime Limited Material Warranty, from the manufacturer, Interlock Roofing Ltd.: material and finish, for as long as the original purchaser owns the home, transferable once. Workmanship is excluded, and ice damming is a stated exclusion. Full terms
30 Year Alunar® Coating Warranty on the finish.
10 Year Limited Labour Warranty from Interlock Metal Roofing (Ontario) Ltd., covering our installation. Labour warranty
Wind resistance warranted to 193 km/h (120 mph) installed to manufacturer specification.

Replacing a roof you'll otherwise replace again

Most of the roofs we replace in Ontario are asphalt. Cedar shakes, concrete tile and natural slate always come off first; a single layer of asphalt can be roofed over only if our inspection finds it suitable. The Interlock® profiles (Slate, Cedar Shingle, Shake, Mediterranean Tile and Standing Seam) weigh roughly 2 to 3.5 kg per square metre and are made in Canada, then installed in Ontario by our own company, as we have done since 1998.

One visit, at your house or on Zoom to start, gets you a fixed price in writing.

Metal roof lifespan: questions, answered

How long does a metal roof last?

It depends on the metal, the coating, the fasteners and the installation. Steel lasts about as long as its protective coating, because it rusts where the coating fails. Aluminum doesn't rust, and aluminum has been known to last over 100 years. That is a property of the metal, not a guarantee; the guarantee is the written warranty.

How long do metal roofs last in Ontario?

Ontario's freeze-thaw cycles, snow and summer sun are hard on roofing that absorbs water or relies on exposed screws. An aluminum roof with concealed fasteners, installed to manufacturer specification with good attic ventilation, avoids the usual failure points. Its material and finish are covered by the Guardian Lifetime Limited Material Warranty and the 30 Year Alunar® Coating Warranty.

Does a metal roof last longer than asphalt shingles?

In published figures, yes. A 2007 study by the US National Association of Home Builders and Bank of America put the life expectancy of asphalt shingles at about 20 years and wood shakes at about 30, noting that local weather, building and design, material quality and maintenance all affect it. Aluminum has been known to last over 100 years.

How long does a steel roof last?

A steel roof lasts about as long as its metallic coating and paint keep water off the steel; where the coating is scratched or cut, steel rusts. We install aluminum, which doesn't rust.

What does the Guardian Lifetime Limited Material Warranty cover?

The Guardian Lifetime Limited Material Warranty covers material and finish for as long as the original purchaser owns the home, and it transfers once. Workmanship is excluded from it; our installation is covered by our own 10-year labour warranty. The finish has a 30 Year Alunar® Coating Warranty. Read the full terms before you sign.

Will the colour fade?

All exterior finishes change with years of sun. The Alunar® finish on Interlock® roofs carries a 30 Year Alunar® Coating Warranty; the terms set out what is covered.

Will a metal roof stop ice dams?

No roof stops ice dams on its own. They come from heat loss into the attic and from ventilation, and ice damming is a stated exclusion of the material warranty. We look at ventilation and insulation with you at the estimate.

What maintenance does a metal roof need?

Keep gutters and valleys clear of leaves and needles, look the roof over after a major storm, and keep attic vents open. With concealed fasteners there are no exposed screws to re-tighten or re-seal.

Sources

Page reviewed October 2026.

Communities we serve in Ontario

Get an aluminum roof priced.

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