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When to Replace a Roof in Ontario: The Signs, the Season, and the Year You Should Not Wait Past
Roofing
When to Replace a Roof, and When in the Year to Do It
Two questions in one. Whether the roof is due is answered by its age, its shingles and its attic. When to book it is answered by the thermometer and the roofer’s calendar, and the two best months of the year are the ones nobody calls in. Both answers are here, in that order.
How long roofs actually last here
| Roof | Rated | Real Ontario life | What ends it |
|---|---|---|---|
| 3-tab asphalt shingles | 20 to 25 years | 15 to 20 | Seal strips let go, tabs blow off |
| Architectural shingles, mid-grade | 30 years to “lifetime” | 22 to 30 | Granule loss, curling at the eaves |
| Premium or Class 4 shingles | Lifetime | 30 to 35 | Same, later |
| Builder-grade shingles on a 2000s subdivision house | 25 years | 15 to 20 | Thin shingles, hot attics, never vented right |
| Metal, exposed fastener | 40 years | 35 to 45 | Screw washers at 20 to 25; panels outlast them |
| Metal shingles or standing seam | 50 years | 50 plus | Paint fades before the metal fails |
| Flat, modified bitumen | 20 years | 18 to 25 | Seams, ponding, flashings |
| Cedar shakes | 30 years | 20 to 40 depending on sun, moss and care | Splitting, moss, cupping |
The gap between rated and real is the attic. A shingle roof over an attic that reaches 60 C every July afternoon because the soffits are blocked ages a third faster than the same shingle over a vented one. Most of the “25-year shingles that lasted 17” in Ontario are a ventilation story, which is why the ventilation page exists and why the new roof should fix it.
The eight signs
From the ground, with binoculars if you have them:
- Curling. Tab corners lifting, or the edges cupping. The asphalt has dried out and the seal has gone. Every wind over 60 km/h will take some now.
- Bald patches. Dark spots where the granules are gone and the black asphalt mat shows. The sun gets at the mat and it cracks within two or three summers.
- Granules in the eavestroughs. A handful of coarse grit every spring is a roof shedding its protection. A few grains is normal.
- Missing shingles or tabs. After a storm on a young roof, a repair. On an old roof, the first of many.
- Moss and black streaks. Streaks are algae and cosmetic. Moss holds water, lifts tabs and is a problem on a north slope under trees. On an old roof, it is a reason; on a young one, a cleaning.
- A wavy or sagging plane. Not the shingles; the deck or a rafter underneath. Needs looking at from inside, and it does not get better.
From the attic, with a flashlight on a bright day:
- Daylight at the eaves, around the chimney or at a vent. Water goes where light does.
- Stains, frost or damp on the underside of the sheathing. One spot is a flashing. A pattern across the roof is the roof, and the deck is now part of the cost.
Two or more of those on a roof over 20 years old is a replacement. One of them on a roof under 15 is a repair; the repair vs. replacement page has the long version.
The year not to wait past
A roof that is shedding granules and curling has maybe two seasons before it leaks somewhere, and the first leak wets insulation, stains a ceiling and, if it lands over a wall, starts rot inside the wall where nobody sees it until the window trim goes soft. The insurance side is worse: insurers in Ontario have started asking the roof’s age at renewal, and some will not write a new policy on a shingle roof over 20 to 25 years without an inspection, and will decline a water claim they can tie to an old roof. The year not to wait past is the one where the roof is 22 to 25 and showing any two signs. After that you are not saving money by waiting; you are deciding which ceiling gets the stain.
When in the year
Late April to early June
The best window. Above 10 C most days so the shingle seal strips bond, crews are fresh and not yet booked solid, and the price is 5 to 10% under July. Book in March.
June to September
Full price and a three-to-six-week wait. Shingles seal fast in the heat, which is good; crews on a black roof at 32 C work shorter days, which is slower. Still fine.
September to late October
The second-best window and the cheapest. Roofers want to fill the calendar before the snow, days are still warm enough, and a roof done now goes into winter new. Book in August.
November to March
Possible on a mild week above 5 C with no snow on the deck; emergency-only otherwise. Shingles go on stiff, seal strips do not bond until spring, and hand-sealing every tab is extra. Metal can go on colder than shingles can. A roof installed at -10 C is a roof to worry about in the first March wind.
Booking it
Get the quotes in the off-season, when roofers have time to measure properly and the calendar is open, and book for April or October. Three quotes on one written scope, which the calculator writes for you, and the quote checklist to compare them. A deposit of 10 to 15% holds the date; anything more than that in February for a roof in May is a roofer using your money for someone else’s shingles.
Questions people ask
How often should a roof be replaced in Ontario?
Architectural shingles every 22 to 30 years; 3-tab every 15 to 20; metal every 40 to 50 plus. Check it at 15 and every two years after that.
What is the best month to replace a roof in Ontario?
May and October. Warm enough for the shingles to seal, roofers not yet or no longer at full capacity, and 5 to 10% off the July price.
Can a roof be replaced in winter in Ontario?
On a mild week above 5 C with a dry deck, a shingle roof can go on with hand-sealed tabs. Below that, shingles crack and do not seal. Metal tolerates cold better. Winter is for emergencies and tarps, not planned replacements.
Will my insurance company make me replace my roof?
Some Ontario insurers ask the roof’s age at renewal and may require an inspection, a higher deductible or replacement on a shingle roof past 20 to 25 years. Ask yours before it is a surprise at renewal.
How do I know how old my roof is?
Purchase documents, the previous owner, the date code on the underside of a shingle, or the look of it: curling, bald and shedding granules is over 20 whatever the paper says.
Look up, then look in the attic
Two signs and twenty years is a roof to price this winter and book for the spring. One sign and twelve years is a repair. The attic settles the ones in between.
Sources and further reading
- IKO: Canadian-made shingles; the warranty and the technical data sheets are on the site.
- Your rights when starting home renovations or repairs: Ontario government. The 10-day cooling-off period, the 10% estimate rule, and what a contract has to say.
- Tarion: the new-home warranty program; the roof on a new build is covered for two years against water penetration, seven years for structure.
