How long does a roof last?

What is the expected life of each material?

The chart below gives the ranges. Read them as ranges rather than numbers, because the spread inside each material is wider than the gap between some materials.

The comparison worth making is not cost per square but cost per year of service. A $550 architectural asphalt roof lasting 25 years is $22 per square per year. A $1,400 standing seam roof lasting 55 years is $25. Those are much closer than the sticker prices suggest, and the metal roof also means one fewer tear-off in your ownership of the house.

Why do two identical roofs last different lengths of time?

Three things, in roughly this order of impact.

Attic ventilation. This is the honest answer to a very large share of “why did my roof only last 15 years” questions. An under-ventilated attic runs hot, and heat cooks the asphalt from underneath — the shingle dries out, loses flexibility, and starts curling years early. In winter the same attic traps moisture, which condenses on the deck and rots it from below. IRC R806.2 sets a minimum net free ventilating area of 1/150 of the vented space, and the 1/300 reduction is an exception requiring two conditions at once, not a free choice.

Installation. Almost everything that fails in the first decade is workmanship, not material: reused flashing, fasteners in the wrong place, a sealant strip that never bonded because the roof went on in the cold. None of it is visible from the ground and none of it is covered by the manufacturer’s material warranty.

Climate. Sustained heat and strong ultraviolet age asphalt fastest. Freeze-thaw cycling spalls concrete tile and cracks clay. Coastal salt attacks the wrong metal alloy. Deep shade grows moss, which holds water against the shingle.

Does the warranty tell me how long it will last?

No, and the gap between the two is a genuine source of grievance.

A “50-year shingle” is a marketing designation attached to a warranty, not a prediction of service life. Manufacturer material warranties are long, prorated — their value declines each year — and cover defects in the product. They generally do not cover a shingle that simply wore out on schedule, and they are void or reduced if the product was installed contrary to the manufacturer’s instructions.

The warranty that matters in the first decade is the contractor’s workmanship warranty, because installation is what fails in the first decade. Read what it covers, how long it runs, and whether it transfers if you sell. See hiring a roofer.

How do I tell how much life is left in mine?

From the ground and from the attic, without going up.

Look for granules in the gutters and at the downspout outlet. Some shedding is normal, especially in the first weeks after installation. Granules accumulating years later mean the surfacing that protects the asphalt from UV is leaving, and the shingle is near the end.

Look for curling and cupping across the whole roof, worst on the sunniest slope. Uniformity is the tell: weather damage is directional and concentrated, age is even.

Look for bald patches where the asphalt shows through.

From inside the attic, look for daylight, damp insulation, staining on the underside of the deck, or rusted nail points — all of which indicate the assembly is letting water or vapour through.

If you know when it was installed, that is better evidence than any of the above. A permit record at your building department frequently has the date.

When should I replace rather than repair?

The honest test is the age of the covering, not the size of the damage.

A localized problem on a roof with substantial life left is a repair. The same problem on a twenty-two-year-old asphalt roof is an argument for replacement, because you are otherwise paying for access to a roof that needs replacing anyway — and you will pay for that access twice.

Be sceptical of a replacement recommendation from whoever is also going to sell you the replacement. That is not an accusation, it is how incentives work, and it is why we treat contractor-published content as a Tier 3 source.

Common mistakes

• Reading the warranty as a lifespan. A 50-year shingle is a warranty designation. The service life is 25 to 35 years on the luxury lines.
• Ignoring ventilation until the roof fails. By the time the shingles are curling, the attic has been cooking them for a decade. Ask about intake and exhaust when you replace, not after.
• Assuming the roof is the problem when the attic is. Poor ventilation, blocked soffits and missing baffles shorten every covering equally.
• Roofing over the old layer. It saves a little now, hides the deck condition entirely, and traps heat that shortens the new roof’s life.
• Comparing materials on price per square instead of price per year. Metal and tile look expensive until the second asphalt tear-off.