What Actually Wears Out a Roof, and in What Order

A roof doesn't wear out in one way. It wears out in several, and they're not equally in your control. Some you can prevent, some you can only slow, and one you can't do anything about. Homeowners waste the most money when they misread which one they're looking at: panicking over the harmless kind, or ignoring the kind that's quietly running the clock down.

To sort out which is which, we talked to two Toronto-area roofers, Dallas of Greater Toronto Roofing and Pamela of Elite Roofing. 

Ask Dallas what does the most damage and he gives you a ranked list: impact first, then ice damming, then rodents, and underneath all of it, slowly, the sun. Here's how to read each one, and where your money and attention are actually worth spending.

Impact: the one you can't plan for

Impact is first on Dallas's list and last on the list of things you can control. A falling branch, a hailstorm, something that physically hits the roof and breaks the surface. Aside from pruning trees near your house, there is no maintenance routine that prevents it and no warning before it happens.

The upside is it's usually obvious and usually local. A branch takes out a section; it doesn't age the whole roof. That makes impact damage a repair, not a reason to replace, unless the hit is severe or the roof was near the end anyway. 

Ice dams: the expensive one, and the fix isn't on the roof

An ice dam forms like this. Heat escapes from your house into the attic and warms the underside of the roof. Snow on the warm part melts, even when it's below freezing outside. The meltwater runs down to the eaves, which hang past the heated part of the house and stay cold, and there it refreezes into a ridge of ice. More meltwater backs up behind that ridge, sits on the shingles, and works its way underneath. Left long enough it rots the roof sheathing, soaks the attic insulation, and stains the ceilings below. 

The cause is attic air leaks and heat loss, not the roof surface. The fix, in order, is to stop warm air leaking into the attic, then insulate the attic properly, then ventilate it so the roof deck stays cold. Get those right and ice dams mostly stop.

"Ice dams don't necessarily mean a bad roof, they just mean you need insulation," Dallas says. He mentions heating cables along the eaves as a cheaper stopgap, with a caveat: squirrels and raccoons chew them up, and you're lucky to get three or four years out of a set. They buy time; they don't fix the cause.

Pamela points out the trap that catches people out: the leak often shows up months late. She had a run of customers reporting spring leaks they blamed on rain, when the water had gotten into the attic from snow weeks earlier and only appeared once things thawed. That lag is what makes an ice-dam leak so easily mistaken for a failing roof when the roof is fine and the attic is the problem.

Rodents: persistent, and worse than they look

Dallas is vivid about it: rodents will "disassemble the shingle as they walk on it," their claws tearing at the surface a little at a time. His advice is to cut off access rather than fight the damage.

The methods run from the low-tech (spikes on the fence they climb) to the odd-but-effective: fox urine, sold at Lee Valley for exactly this, which farmers use to keep smaller animals off crops (the smell of a bigger predator moves them along).

And if the scratching is coming from inside the attic rather than across the shingles, that's a different job with its own rules.

The sun: the one you can't stop, and mostly don't need to

"The sun, you can't hide from it," Dallas says. It's last on his list, but it's the one every roof gets, on every clear day, for its whole life. Pamela adds wind to that list, working at the shingles alongside the sun season after season. This is the slow killer, and the one homeowners most often misread.

The sun's calling card is a roof that's faded from black to gray, and that graying is exactly what makes people think they need a new roof when they often don't.

The colour on an asphalt shingle comes from a layer of granules, and those granules aren't what keeps water out. "The granular spray is not a waterproofing agent, it's to reflect the sunlight," Dallas says. Their real job is UV protection, shielding the asphalt underneath. As the roof ages that layer weathers and the colour dulls. That fading isn't failure, it's the sun protection being slowly spent, and it happens to every roof.

But before you read a colour change as aging, work out which kind you're looking at, because one is fixable and one isn't. Dark streaks and blotches are usually algae and dirt, and a cleaning brings the colour back. True fading, the granules dulling from years of UV, is different: nothing you spray or paint on restores it, and painting shingles can trap moisture and void the warranty.

If it's biological, clean it. If it's age, leave it alone.

What actually matters comes later, when the granules stop just dulling and start washing off, leaving bare asphalt exposed. That shows up as grit in your gutters, and it's one of the standard signs a roof is wearing out. You can't re-granule a shingle, so widespread granule loss on an older roof points toward replacement, not repair. With the weather we have in the GTA that usually lands somewhere in the fifteen-to-twenty-five-year range, a bit sooner than the twenty-to-thirty you'll see quoted for milder places.

What's actually in your control

Most of what wears a roof out is slow, hidden, or out of your hands. The short list of things you can actually do is worth doing well: keep gutters clear so meltwater and rain drain properly, trim back branches that both scrape the shingles and give squirrels a bridge onto the roof, and never pressure-wash asphalt shingles, which blasts off the granules that protect them. One habit that costs nothing: once a season, look over every side of the roof from the ground with binoculars and take a photo, so a real change stands out from normal aging.

Remember that replacing your roof won't fix the attic

Ice damming does the costliest preventable damage in this climate, and the fix lives in the attic.

That sets two traps.

The first: replacing your shingles won't stop ice dams.Ice dams are caused by attic air leaks (not the roof surface), and a new roof does not automatically improve what's underneath it. If you want the work that actually prevents ice dams, you have to ask for it.

The second: fixing the attic prevents future dams, but it doesn't undo the damage past ones already did. Air sealing and insulation stop the heat loss that causes the problem. They don't un-rot sheathing or dry out soaked insulation. If ice dams have been forming for a few winters, you may be looking at two jobs, the attic work that stops it recurring, and repairs to whatever the water already reached.