How much does a roof replacement cost in Ontario in 2026?

A full asphalt shingle replacement runs roughly $8,250 to $19,000, with most houses in the middle of that range. It covers a tear-off to the deck, sheathing repair where needed, ice-and-water membrane at the eaves and valleys, underlayment, new flashing at every penetration and the shingles themselves. Reusing old flashing is the most common way a quote comes in low.

Why is a Stratford roof more expensive than a Chatham one?

Because it has more to survive. Environment Canada normals put Stratford at about 218 cm of snow a year and Chatham at 79. The snowbelt end needs more ice-and-water membrane coverage, genuine soffit-to-ridge ventilation and careful eave detail. The Erie shore end spends that money on wind instead — uplift rating, six-nail patterns and starter course.

What does the price per square actually depend on?

Roof area and pitch set the base, and then the junctions decide the rest. A simple post-war gable in Sarnia and a Victorian in Stratford with five dormers and three valleys are not the same job at the same rate. Every dormer, valley, chimney and skylight is flashing work, and flashing is where roofs leak.

Should I get the cheapest quote?

Compare what is in them before comparing the numbers. The three things that separate a low quote from a fair one are whether the flashing is being replaced or reused, how far the ice-and-water membrane runs up from the eave, and whether the deck is being inspected after tear-off or assumed sound. All three are invisible once the shingles are on.

Does a new roof help with insurance?

Frequently, yes. Roof age has moved from a detail to a rating factor, and some underwriters will not write a policy past a certain age, or will write it on actual cash value rather than replacement cost. That is the difference between a new roof and a depreciated cheque after a storm, so it is worth asking your insurer what they want before you book.

What Does a Roof Cost in Southwestern Ontario?

Nobody replaces a roof because it turned twenty. They replace it after the second leak, or after an insurer asks a pointed question at renewal, or after finally looking in the eavestrough and finding it full of granules.

The published Ontario range for 2026 is $8,250 to $19,000. That is a wide band, and if you are staring at two quotes several thousand dollars apart, five things explain almost all of it.

1. Which end of this corridor you are on

This is the one nobody puts on a quote, and it changes the specification more than anything else does.

Environment Canada normals put Chatham at about 79 cm of snow a year and Stratford at 218 cm. That is nearly three times the load, measured at reporting stations in each town. Inland of Goderich and Listowel, in the Huron snowbelt proper, the nearest stations run higher again.

Snow that sits on a roof for weeks is what makes an ice dam, and an ice dam is what forces water backwards under a shingle lap that was only ever designed to shed water running downhill. So at the north end of this service area the money goes into ice-and-water membrane coverage, ventilation and eave detail.

At the Erie shore end it goes somewhere else entirely. Leamington, Chatham and Simcoe sit in the most tornado-active corner of Canada — Western University’s Northern Tornadoes Project maps it every season — and far more common than a tornado is the straight-line wind from the same storms. There the money goes into shingle uplift rating, nailing pattern and the starter course.

Neither spec is better than the other. They are answers to different questions, and a quote written for one and used on the other is quietly under-built — you just will not find out for about eight winters.

2. The junctions, not the area

Area and pitch set the base. After that, you are paying for the interruptions.

Every dormer, valley, chimney, skylight and roof-to-wall junction is flashing work, and flashing is slow, skilled and where roofs actually leak. A simple post-war gable in Sarnia with wide uninterrupted planes is genuinely cheaper per square than a Victorian in Stratford or St Thomas with dormers on three elevations.

Which is why an estimate from an aerial photograph goes so wrong on older housing. The software measures area beautifully. It has no idea about the step flashing behind the rear addition somebody built in 1962 — and on a Victorian, that is most of the skilled work.

3. What the deck turns out to be

Nobody can assess a deck without taking the old shingles off. Nobody. Anyone who says otherwise is guessing, and a quote that stays silent on it is either hiding a variation or quietly hoping for the best.

What a good quote does instead is carry a stated rate for replacing rotten sheets, and an honest estimate of how many it expects to find. That way the number moves for a reason you can see.

This is also the argument against going over the old shingles. A second layer is cheaper on the day, adds weight in the part of this corridor that already carries the most snow, and hides the one part of the roof worth seeing. Where the deck is known sound and the snow load is low it can be defensible. In the snowbelt it rarely is.

4. Flashing: replaced, or reused

This is the single most common way a quote comes in low, and it is worth knowing about.

Old flashing at a chimney or a wall junction can be left where it is and new shingles laid around it. Saves a few hundred dollars. Also puts twenty-five-year-old metal under a brand new roof, so the next leak arrives long before the shingles are anywhere near finished.

Just ask outright. One line, and it matters more than the brand on the bundle.

5. Access, and the season

A two-storey with no driveway access for a dump trailer costs more than a bungalow with a clear approach, because everything comes down by hand.

Season matters here too. Asphalt shingles need warmth to seal properly, and a roof laid in a cold snap has to hand-seal or wait for spring sun to bond. That is not a reason to refuse winter work — an active leak does not wait — but it is a reason to plan a discretionary replacement for the shoulder seasons.

What we will tell you not to spend money on

A roof with ten good years in it and one failed stack boot needs a boot. Cheap part, short job, and honestly a large share of the calls we get. The rubber collar splits after two decades of sun, water runs down the outside of the pipe, and the stain turns up a metre away looking like something far more serious.

Premium shingles on a low-exposure roof. On a sheltered plane in Woodstock or Ingersoll the upgrade buys warranty length rather than performance. On an exposed elevation in Sarnia or on the Erie shore, the higher uplift rating is doing real work. The money is well spent in one case and decorative in the other.

A full replacement on a roof with one bad valley. Repairing a valley is a day. Replacing a roof because of one is an expensive way to solve the wrong problem, and the written findings will say so.