New Brunswick · Roof lifespan guide

How long does a metal roof last in New Brunswick?

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.

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 Maritime weather does to a roof

A roof near the Atlantic works through salt air, fog, wind-driven rain, winter thaws and heavy snow every year, with post-tropical storms on top. Each of those finds a different weak point.

Salt air and fog

Salt air shortens the life of a steel roof: it is highly corrosive to steel once the protective coating is scratched or cut. Fog is part of coastal life here; the Nova Scotia Museum's Natural History of Nova Scotia puts fog on the province's coasts 15 to 25 per cent of the year. Aluminum cannot rust, because it forms its own protective oxide layer, so a house on the shore doesn't need a different roof from one inland.

Wind-driven rain and storms

Wind is what usually takes an asphalt roof early. Hurricane Fiona, on September 24, 2022, caused over $800 million in insured damage, the most costly extreme weather event ever recorded in Atlantic Canada, according to the Insurance Bureau of Canada. Research by the Insurance Institute for Business & Home Safety found that most asphalt shingles begin to lose wind performance between years five and 10, and that shingles losing their sealant bond is the single greatest cause. Interlock® panels lock on all four sides with no tab for the wind to lift, and wind resistance is warranted to 193 km/h (120 mph) installed to manufacturer specification. Hurricane-force wind damage is a matter for your home insurance and is excluded from our labour warranty.

Winter thaws and freeze-thaw

Maritime winters swing above and below freezing. Storms that track over New Brunswick bring warm southwest winds and thaws to Nova Scotia, and mild ocean air regularly replaces the cold, according to the Nova Scotia Museum. Water that gets into a roofing material freezes, expands and thaws, over and over: asphalt granules loosen and wood splits. Aluminum absorbs no water, so there is nothing in the panel for freeze-thaw to work on.

Heavy, wet snow

Coastal snow is often heavy and wet, and it can load a roof for days before rain or a thaw takes it away. Metal sheds snow; where a slide would land on an entry, a deck or a walkway, snow guards go in, planned 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.

A short season for asphalt

Asphalt shingles need warmth to seal. The Insurance Bureau of Canada advises replacing asphalt shingles in weather of at least 10 °C to improve their quality and longevity, and a Maritime roofing season has fewer of those days at each end. Interlock® panels are locked mechanically, not sealed by heat.

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
RoofLife expectancyBasisWhat to know
Asphalt shinglesAbout 20 yearsNAHB / Bank of America study (2007)When it is done, it comes off or, if suitable, is roofed over once.
Wood shakesAbout 30 yearsNAHB / 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® aluminumAluminum has been known to last over 100 yearsA property of the metal, not a guaranteeThe 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 New Brunswick.

  • 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 Maritime Metal Roofing 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

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 New Brunswick by our own company, Maritime Metal Roofing Ltd., founded in 2007.

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 the Maritimes?

Salt air, wind-driven rain, post-tropical storms, winter thaws and heavy snow are hard on roofing that rusts, absorbs water, relies on a heat-activated seal or uses exposed screws. An aluminum roof with concealed fasteners, installed to manufacturer specification with good attic ventilation, avoids those 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.

Does salt air shorten the life of a metal roof?

It shortens the life of steel. Salt air is highly corrosive to steel once its protective coating is scratched or cut, and the exposed metal can begin to rust. Aluminum cannot rust: it forms a thin oxide layer that seals the surface and re-forms if scratched. Interlock® roofs are heavy-gauge aluminum.

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, and near the ocean that happens faster. 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, which is not transferable and excludes hurricane-force winds, wind storms, hail, ice damming, and snow and ice shedding. The finish has a 30 Year Alunar® Coating Warranty. Read the full terms before you sign.

Will a metal roof survive a hurricane?

No roofer can promise that any roof will come through any storm. Interlock® roofs are warranted for wind resistance to 193 km/h (120 mph) installed to manufacturer specification, with panels locked on all four sides and fasteners concealed. Damage from hurricane-force winds is a matter for your home insurance, and it is excluded from our labour warranty.

Will the colour fade?

All exterior finishes change with years of sun and weather. 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.

Get an aluminum roof priced.

A fixed price in writing after one visit. Maritime Metal Roofing Ltd. · 101 Thornhill Dr #105, Dartmouth, NS B3B 1S2

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