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Roof Replacement in Ontario: What It Costs, How to Measure It, and When to Do It
RoofingReplacement
Roof Replacement in Ontario: The Cost, the Measuring, the Tear-Off, and the Year to Do It
Installed prices by the square, three real roofs priced through to HST, and the decisions that come before the quote.
The quote is the last step. Before it, you need to know roughly how many squares you have, what is under the shingles, whether the roof actually needs to come off this year, and what a fair installed rate is for the system you want. Do those four in order and the three quotes stop looking random.
The numbers
19squares on a 1,600 sq ft 6/12 bungalow
$675per square, architectural shingles installed
$120per sheet of decking replaced
13%HST, never in the number in your head
The guides
Roof replacement cost in Ontario
Shingles, metal and flat, installed rates by the square, and three real roofs priced all the way to HST.
Roofing cost per square
What a square is, what the per-square number has in it, and how to check a quote against it in two minutes.
How to measure a roof from the ground
Footprint, overhangs, pitch factor, squares. The arithmetic the roofer does on your driveway.
Tear-off and decking cost
Layers, disposal, plywood and OSB, board decks, and the unit price that has to be on the quote before the roof comes off.
Repair or replace?
The attic decides, not the shingles. The age, the deck and the number of problems, and where repair stops making sense.
When to replace a roof in Ontario
The signs, the season to book, and the year you should not wait past if the last roof went on in a hurry.
The calculators
Roof replacement cost calculator
Footprint and pitch to roof surface, then shingles, metal or membrane at Ontario installed rates, tear-off, decking, flashing, venting and HST. Writes a scope you can send to three roofers.
Metal roof cost calculator
Standing seam, metal shingles or panels, with snow guards and the 40-year cost against shingles done twice. The number that decides metal or not.
Roofing material calculator
Bundles, underlayment rolls, ice and water, nails and ridge cap for a given roof. For the people doing it themselves or checking the material line on a quote.
Ontario snow load calculator
The design snow load for your municipality, which is why a cottage roof in Parry Sound is framed heavier than one in Windsor.
The order to do it in
- Go in the attic with a flashlight. Daylight at the eaves, black sheathing, frost in February, wet insulation under the bathroom. Ten minutes up there tells you more than an hour on the lawn. Repair or replace starts there.
- Measure the roof. Footprint plus overhangs, times the pitch factor. Write the squares on the fridge. How.
- Price it yourself first. The calculator gives you a range and a written scope. Three roofers pricing the same scope is the only way three quotes compare.
- Pick the system, then the roofer. Shingle roofers and metal roofers are mostly different companies. Decide what goes on before you decide who puts it on.
- Book for the shoulder season. Late April to June and September to early November. Shingles need 40 F and up to seal; July heat scuffs them; December asks the roofer to hand-seal every tab. When to replace a roof.
Have a quote in hand? Let a builder read it first
For $99, I read your roofing quotes and your roof photos and send back a written note: what is missing from the scope, where the price is out of line with October 2026 Ontario rates, what to ask the roofer before you sign, and whether the roof should come off at all this year. Two business days. How the roofing quote review works.
