What Drives The Price
Two quotes on the same Toronto roof can differ by half, and almost all of the difference is in things the quote does not mention.
Short answer
The cost drivers are area and pitch, number of existing layers, the condition of the decking, the complexity of the roof, the material, access and disposal, and how much flashing and ventilation work is included. The cheapest quote is usually the one that excludes the most.
The variables
Roof area and pitch. A steep roof is slower and needs more safety provision, which is real cost rather than padding.
Number of existing layers, because two layers means a heavier tear-off and more disposal.
Decking condition, which cannot be known until the tear-off and which is the single most common source of a revised price.
Complexity: valleys, dormers, hips, skylights, chimneys, multiple planes. A cut-up roof costs far more per square than a simple gable.
Material, from standard three-tab through architectural shingles to metal, which is a different order of cost.
And access and disposal, which on a narrow Toronto lot with no driveway and a rear laneway is a genuine factor.
Ask what happens to the decking
Every roof quote should state the rate for replacing sheathing and roughly how it will be assessed. A quote with no decking provision is either going to surprise you or going to leave bad sheathing in place under a new roof. On older Toronto housing with plank decking, some replacement is normal rather than exceptional.
What should be in writing
Tear-off to the deck versus an overlay, stated explicitly.
Underlayment specification, and ice and water shield at the eaves, valleys and penetrations — which in Toronto is not optional.
Drip edge and starter strip, which are frequently omitted on a cheap quote.
All flashing: chimney, sidewall, valley, vent boots and skylights, with new material rather than reusing the old.
Ventilation work: intake, exhaust, baffles, and what happens to any fan discharging into the attic.
And the decking rate, the disposal, the permit if one is required, and the warranty terms in writing.
Where the cheap quote saves money
Overlaying rather than tearing off, which hides the deck and shortens the new roof life.
Reusing old flashing, which is where the next leak comes from.
Omitting ice and water shield, or running it only a token distance up from the eave.
No drip edge, which lets water run behind the fascia.
Leaving the ventilation exactly as it was, including a bath fan in the attic.
And no written decking provision, which means the conversation happens on day two with the roof open.
Common questions
Why are the quotes so different?
Usually what is excluded: tear-off, flashing, ice and water shield, drip edge and ventilation.
Will the decking need replacing?
Some, on older Toronto housing with plank decking. Get the rate in writing up front.
Is ice and water shield necessary?
In Toronto, yes. At the eaves, the valleys and every penetration.