Price a replacement from the roof surface
Roofing contractors price the surface they must cover, which is usually larger than the building's flat footprint. Use measured sloped area from a survey or obtain it from the roof pitch and roofing quantity tools. This page begins with that area and combines the replacement quote with stripping, disposal and fixed extras. It is a budget worksheet for an already specified roof. It does not choose a covering system, determine the condition of the deck or calculate a safe roof structure.
Keep removal and fixed work visible
Base quote = sloped area × installed rate + sloped area × tear-off rate + fixed extrasThe installed rate can include covering, underlayment, fasteners and labour, depending on the quote. Check its written scope. A separate tear-off rate helps compare retaining an existing covering with stripping it, but enter zero if removal is already included in the installed rate. Fixed extras may represent scaffolding, flashing, ridge work, delivery or an explicit deck-repair allowance. These costs are not all proportional to roof area. Contingency multiplies the combined base quote and is displayed separately. There is no automatic material waste factor because an installed-area quotation may already include the contractor's ordering loss.
Example for a 120-square-metre roof
An actual roof surface of 120 square metres at an installed replacement rate of 75 costs 9,000. Removal and disposal at 12 per square metre add 1,440. Fixed extras of 1,500 bring the quote total to 11,940 currency units. A 10 percent contingency adds 1,194, producing a replacement budget of 13,134. The sample numbers illustrate the method and are not a statement of current roofing prices. For an imperial quote, enter its square-foot area and rates per square foot. A price per roofing square must be divided by 100 before using a square-foot rate field.
Compare scope as well as totals
A low area rate may omit access equipment or complicated edges. Ask how valleys, chimneys, penetrations, ventilation and damaged decking are treated. Establish whether the price covers one old layer or additional layers discovered during removal. Record any allowance for weather protection and who handles disposal. Include taxes consistently in each quoted number because this estimator does not calculate them separately. Do not measure an elevated roof by walking on it for the sake of a budget; use an existing plan, ground-based measurements or a professional survey. The final result is only as complete as the allowances you enter. Keep an itemised contractor scope next to it, especially where concealed repairs will be authorised and charged later, so the reserve does not disguise omissions in the base quotation.
Frequently asked questions
Should I enter the house footprint?
Enter actual sloped roof surface including the areas in the quoted scope. Use the roofing calculator to turn footprint and pitch into a surface estimate.
What if the quote is per roofing square?
One roofing square is 100 square feet. Divide a quoted price per square by 100 before entering it as a price per square foot.
Is removal always an extra cost?
It depends on the quote. Enter a separate tear-off rate only when it is excluded from the installed replacement rate.
Are the default amounts contractor prices?
No. They are example inputs for arithmetic. Substitute written local quotations for the covering, removal and fixed work.
Does the tool inspect structural damage?
No. Concealed decking or structural repairs require inspection. Enter an agreed allowance if relevant and retain the survey findings separately.
Last reviewed: 2026-10-03 · How we calculate