Questions covered in this guide
Identify what will be removed
Ask each bidder whether the proposal removes the existing covering or installs over it. GAF says overlay suitability depends on roof condition and applicable local requirements. It also explains that removing old roofing allows the contractor to inspect the deck. An overlay price and a tear-off price therefore need a scope comparison before their totals are useful.
Ask how the roof was evaluated
Request the observed number of existing layers and the basis for that answer. Have the roofer explain any signs of deterioration or leakage that affect the proposal. Ask which findings support the recommended approach and which conditions remain unknown. The answer should refer to your roof and the selected product, not a universal claim that another layer is always permitted or always prohibited.
Compare access to hidden work
Make rows for deck inspection, damaged decking, flashing, underlayment, removal and disposal. Ask what each approach includes and how a concealed problem would be handled. If a condition cannot be priced until removal, request the change-order method and the evidence you will receive before authorizing extra work. Keep an unresolved condition visible instead of treating the absence of a line item as proof that no repair is needed.
Resolve the approved scope before budgeting
Ask the contractor to confirm the applicable permit route and manufacturer's installation requirements for the proposed approach. Keep that explanation with the quote. The roofing calculator's national range is a planning reference; it does not determine overlay eligibility or inspect existing layers. Use supplied prices for clearly described alternatives, with removal and disposal counted consistently. If the scope changes after inspection, revise the comparison before interpreting the difference as a saving.
Putting it into practice
The bid comparison focuses on what each approach exposes and how concealed work will be authorized. Removal, inspection and disposal remain visible so a lower total is not treated as an equivalent scope.
Sources and supported claims
GAF says overlay suitability depends on the existing roof condition and local building requirements.
Source ↗ · national · Checked 2026-10-12
GAF explains that tearing off existing roofing permits inspection of the underlying deck.
Source ↗ · national · Checked 2026-10-12