Idaho · Roof lifespan guide
How long does a metal roof last in Idaho?
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 put in writing 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 promise.
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 color.
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 color 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 120 mph when installed to manufacturer specification.
What Idaho weather does to a roof
A roof here works through freezing nights and sunny days all winter, snow, spring and summer hail, and long, hot, dry summers every year. Each of those finds a different weak point.
Freeze–thaw
Treasure Valley winters swing between freezing nights and sunny afternoons. Water that soaks into wood or works under a curled asphalt tab freezes, expands and opens the gap a little more each time. Aluminum absorbs no water and can't rot or split, and interlocked panels leave no tab edge to lift.
Hail
Spring and summer thunderstorms bring hail: on June 26, 2026 a storm left several inches of small hail on the ground in northwest Meridian. Hail knocks granules off asphalt and splits brittle shakes. Interlock's Slate, Cedar Shingle, Shake and Mediterranean Tile profiles carry a UL 2218 Class 4 impact rating, verified by Intertek for Delta Building Products; large hail can still dent aluminum.
Summer sun
Long, hot, dry summers bake asphalt and dry out wood. Aluminum doesn't care about heat; the finish carries the color, and the Alunar® finish has a 30 Year Alunar® Coating Warranty.
Snow, valley and mountain
The University of Idaho's 2015 ground snow load study lists 15 psf for Boise and 157 psf for McCall: loads climb fast with elevation. Metal sheds snow; where a slide would land on an entry, a deck or a walkway, snow guards go in, planned at the estimate. Ice dams come from heat escaping into the attic and from ventilation, not from the roof covering; no roof prevents them on its own, and ice damming is a stated exclusion of the material warranty.
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.
| Roof | Life expectancy | Basis | What to know |
|---|---|---|---|
| Asphalt shingles | About 20 years | NAHB / Bank of America study (2007) | The most common roof in the Treasure Valley. When it is done, it comes off or, if suitable and your city allows it, is roofed over once. |
| Wood shakes | About 30 years | NAHB / Bank of America study (2007) | Needs cleaning and re-treating, dries and splits in sun and freeze–thaw, and is a fire load in wildfire country. 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 promise | What is promised 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 promised in writing are two different things. Here is what is in writing on an Interlock® roof installed in Idaho.
- Guardian Lifetime Limited Material Warranty, from the manufacturer, Interlock Roofing: material and finish, for as long as the original purchaser owns the home, transferable once. The second owner is covered to 50 years from substantial completion. Workmanship is excluded, and ice damming is a stated exclusion. Full warranty (PDF)
- 30 Year Alunar® Coating Warranty on the finish.
- 10 Year Limited Labor Warranty from Interlock Metal Roofing (PNW) Inc.: our 10 Year Limited Labor Warranty covers the installation, for ten years from the Substantial Completion Date. Labor warranty
- Wind resistance warranted to 120 mph when installed to manufacturer specification.
Replacing a roof you'll otherwise replace again
Most roofs in the Treasure Valley 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 0.4 to 0.7 lb per square foot and are made in North America by Interlock Roofing at its plant in Delta, BC, then installed in Idaho by our own company, as we have done since 1997.
Book a roof consultation at your house, or over Zoom to start, and you get a written price after your roof consultation.
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 promise; what is promised is in the written warranty.
How long do metal roofs last in Idaho?
Freeze–thaw, hail, hot summer sun and snow 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 for as long as the original purchaser owns the home, and our 10 Year Limited Labor Warranty covers the installation.
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 10 Year Limited Labor Warranty covers the installation. The finish has a 30 Year Alunar® Coating Warranty. Read the full terms before you sign.
Will the color 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, needles and windblown debris (embers collect where debris does), trim back branches over the roof, 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
- National Association of Home Builders / Bank of America Home Equity: Study of Life Expectancy of Home Components (February 2007)
- Guardian Lifetime Limited Material Warranty (full document, PDF)
- 10 Year Limited Labor Warranty (Form 5335)
- ICC-ES Evaluation Report ESR-1790, Interlock Roofing, reissued September 2025 (PDF)
- University of Idaho, Department of Civil Engineering: Ground Snow Loads for Idaho, 2015 Edition
- East Idaho News, June 27, 2026: "Lightning, hail, heavy rain hit Boise area, causing flooding, emergency declarations"
- Interlock Roofing: the aluminum roofing system
Page reviewed October 2026.
Get an aluminum roof priced.
A written price after your roof consultation. Interlock Metal Roofing (PNW) Inc. · 3295 W Elder St, Suite 209, Boise, ID 83705
