Roof Replacement Cost: How Roofing Quotes Are Actually Built

Everything in roofing is priced per square

A roofing square is 100 square feet of finished roof surface. Every material price, labour rate, tear-off charge and disposal fee in the trade is quoted against that unit, which is why a contractor who has walked your roof can produce a number in minutes. If you want to understand a quote — or challenge one — you have to work in the same unit they do.

The trap is that the square counts sloped surface, not the footprint of the house. A 2,000 square foot ranch does not have 20 squares of roof. Multiply the footprint by the pitch multiplier first: 1.118 at 6:12, 1.202 at 8:12, 1.414 at 12:12. Then add the overhangs, which are real roof surface even though they sit outside the walls. A 2,000 sq ft footprint at 6:12 with two-foot eaves is closer to 24 squares than 20 — a 20% error if you skip the step.

What each covering costs installed

Installed cost bundles the covering, underlayment, fasteners, starter and ridge, and the labour to fit them. The ranges below are broad national figures from published trade cost guides; your local market can sit outside them in either direction, which is exactly why the calculator asks you for rates instead of guessing.

Divide the installed range by the service life and the picture changes. Architectural asphalt at $600 per square over 28 years is about $21 per square per year. Standing seam at $1,400 over 55 years is about $25. The premium products are not four times more expensive over the life of the building; they are more expensive to finance today and cheaper in disruption later.

Labour, tear-off and disposal

On a straightforward asphalt re-roof, labour is usually the largest single line — commonly 55% to 65% of the total. It pays for the crew, the staging, the fall protection, the dumpster placement and the clean-up sweep. It is also the line that varies most between contractors, because it reflects crew productivity and the risk they price into your particular roof.

Tear-off is billed separately for a reason: it is a different activity with a disposal cost attached. One layer of asphalt shingles typically adds $100 to $150 per square. A second layer costs more than the first because the crew is now handling twice the tonnage. Heavy materials — concrete tile, slate, multiple layers over board sheathing — can double that figure once landfill tipping fees are included.

• One layer asphalt tear-off: about $100–$150 per square.
• Two layers: roughly 1.6× the single-layer rate, not 2× — the setup is shared.
• Tile or slate removal: $200–$400 per square with heavier disposal costs.
• New construction or a legal overlay: zero tear-off, but overlays hide deck damage.

Steepness, storeys and complexity: the legitimate surcharges

Two quotes on roofs of identical area can legitimately differ by 40%. The reason is almost always crew hours per square, and three variables drive it: how steep the roof is, how high off the ground it is, and how cut up the geometry is.

Steepness is the cleanest to reason about. Up to about 7:12 a competent crew walks the roof and works at normal speed. Beyond that, roof jacks, planks and harnesses come out, material has to be carried rather than slid, and output per hour falls. A reasonable rule is 5% added labour per half-pitch above 7:12, which is what our estimator applies internally.

These multiply. A complex 9:12 roof on a two-storey house carries a labour factor of about 1.10 × 1.35 × 1.10 = 1.63. On a $300 per square labour rate that is $489 per square — and the contractor quoting it is not gouging you, they are pricing the job in front of them.

The extras that appear after tear-off

The single most common change order on a residential re-roof is deck replacement. Nobody can see the condition of the sheathing until the covering is off, so responsible contractors quote a per-sheet rate up front — typically $70 to $120 per sheet of 4x8 plywood or OSB, installed. Ask for that rate in writing before work starts and you avoid the worst argument in roofing.

• Deck sheets: $70–$120 each installed, quantity unknown until strip-out.
• Chimney flashing rebuild: $300–$1,000 depending on chimney size and material.
• Skylight replacement: $600–$1,800 each — replace at re-roof or never.
• Ventilation upgrades to meet code: $200–$800.
• Permit and inspection fees: $150–$700 depending on jurisdiction.
• Ice and water shield in cold climates: often required at eaves and valleys by code.

How to compare three quotes fairly

Never compare bottom-line totals. Convert every bid to a cost per square and then check that the scope behind each number is the same. Most of the time the cheapest quote is cheap because something has been left out, and the expensive one is expensive because the estimator measured the valleys properly.

1. Confirm the roof area each contractor measured, in squares, and reconcile any difference over 5%.
2. Confirm how many layers are being removed and where the debris is going.
3. Confirm the underlayment type and the ice-and-water coverage at eaves, valleys and penetrations.
4. Confirm whether all step, apron and chimney flashing is new or reused.
5. Confirm the ventilation plan — intake as well as exhaust.
6. Confirm the deck-sheet rate, the warranty terms and who registers the manufacturer warranty.

When those six items match, a per-square comparison is genuinely apples to apples, and the remaining spread is contractor overhead, crew quality and schedule — all legitimate reasons to pay more or less.

Worked example: a 1,600 sq ft footprint at 6:12

Take a single-storey gable house, 1,600 sq ft of footprint including overhangs, 6:12 pitch, architectural shingles, one layer coming off.

1. Sloped area: 1,600 × 1.1180 = 1,789 sq ft, or 17.89 squares.
2. Material at $150 per square with 10% waste: 17.89 × 1.10 × $150 = $2,952.
3. Labour at $300 per square, labour factor 1.00: 17.89 × $300 = $5,367.
4. Tear-off at $125 per square: 17.89 × $125 = $2,236.
5. Flashing, vents and permit allowance: $900.
6. Total: $11,455, or about $640 per square.
7. Budget with 10% contingency: about $12,600.

Now change one variable. Put the same roof on a two-storey house at 10:12 with a couple of dormers: the labour factor becomes 1.15 × 1.15 × 1.10 = 1.45, labour rises to $7,782, and the total moves to roughly $13,900 before contingency. The material bill barely moved. That is the shape of nearly every roofing quote disagreement.

Where you can and cannot save

There are real savings available and there are false ones. Scheduling in the shoulder season, bundling with neighbours, and choosing a mid-range architectural shingle over a designer profile all save money without costing you performance.

• Real saving: off-peak scheduling — late autumn and early spring crews are hungrier.
• Real saving: skip designer shingles; the mid-tier architectural product carries the same warranty class.
• False saving: overlaying instead of tearing off. It traps heat, adds load and hides rot.
• False saving: reusing flashing. It is the cheapest component and the most common leak source.
• False saving: skipping ice-and-water shield in a cold climate. One ice dam erases the saving.
• False saving: the unlicensed, uninsured cash quote. You own the liability.

If the budget genuinely will not stretch, the honest move is to phase the work by roof plane or postpone by a season with targeted repairs — not to thin the specification on the plane you are replacing.

Frequently asked questions