Questions covered in this guide
A shingle price does not answer the decking question
Decking is the supporting surface below the roof covering. GAF recommends asking a contractor about the cause of decking damage, the proposed material and its effect on the quote. Before the roof is opened, agree on how newly discovered work will be documented and priced. An allowance is a budgeting choice, not proof that a particular amount of damage exists.
Define the unit before comparing it
Ask whether a repair price is per sheet, square foot or another unit. Record the specified material and thickness, labor, removal, disposal and any other inclusions. A lower unit number can buy a different scope. If the proposal includes some decking already, record that included quantity separately from the price of additional work. Ask how partial units will be counted.
Use an illustrative change order
Suppose a hypothetical contract includes two replacement sheets and an inspection documents five sheets needing replacement. If that contract counts full sheets, three are additional. Multiply those three by the agreed additional-sheet price, then add only separately authorized work. This is a quantity example with no market price or assessment of your roof. A different contract might count square feet or use a different included allowance.
Agree on the communication path
Identify who receives photographs, confirms quantities and approves the extra charge. Ask what happens if that person cannot be reached while the roof is open, including the contractor’s weather-protection plan. Keep the final repair record and invoice together. The roof calculator lets you carry your own extra-work amount, but it cannot predict concealed damage. Leave unresolved quantities visible until the contractor can document them; do not convert uncertainty into a fabricated decking total.
What should an extra-decking price actually include?
Before tear-off, ask for one written line identifying material, thickness, unit size, removal, installation, disposal and the quantity included in the base quote. Record whether partial sheets are rounded up and whether a minimum charge applies. A hardware-store sheet price is not an installed repair quote. GAF’s decking guide recommends asking what caused damage, which material will replace it and how the repair affects the quote.
How do two decking allowances change the total?
In the invented example above, five documented replacement sheets make Proposal A’s total $14,360 and Proposal B’s total $14,300. If six equivalent sheets are needed instead, the totals become $14,480 and $14,440. Those are scenarios using assumed contract terms, not evidence about your roof. Leave the quantity unknown until it is documented, and ask the contractor to identify any work outside the unit price. Do not count the included sheets again.
Get a roof price with the extra-work method attached
Start with the roof replacement calculator for a broad budget, then request roofing quotes. Describe whether you are planning a replacement, repair or inspection and when you need it. Include the request for a written decking allowance and additional-unit price. You do not need to climb onto the roof or guess how many sheets are damaged. Actual scope and pricing require a contractor’s assessment.
Putting it into practice
A two-proposal example calculates the base price plus only sheets beyond each included allowance. A five-sheet and six-sheet scenario exposes quantity sensitivity without inventing a damage forecast. The table defines the unit before comparing prices and leads directly to a roofing quote request.
Sources and supported claims
GAF describes decking as a supporting part of the roof assembly and advises asking what caused damage.
Source ↗ · national · Checked 2026-10-14
GAF recommends asking about proposed replacement material and how decking repairs affect the quote.
Source ↗ · national · Checked 2026-10-14