Send one consistent brief
Give each contractor the same description of the building, known roof issues, access and desired result. Provide available drawings and photographs. Mark uncertain information plainly so a bidder can identify what needs inspection rather than silently pricing an assumption.
Separate the work packages
Compare removal, disposal, substrate repairs, roof components, flashings and drainage interfaces. Include protection of the property and cleanup. A low total may cover fewer tasks; the comparison should make those differences visible before you choose.
Clarify allowances and unknowns
Ask what quantities or conditions are assumed and how changes would be identified, priced and approved. Request a written process for concealed damage rather than assuming it is either fully included or always excluded. The agreement should reflect the actual project and appropriate advice.
Compare evidence as well as price
Review relevant references, proposed products and actual warranty documents. Confirm responsibilities for scheduling, inspections and handover. Record unanswered questions beside the quotation so a persuasive presentation does not substitute for a complete scope.
Build a comparison sheet
Use one row for each scope item: existing roof removal, disposal, deck inspection, allowances for concealed damage, underlayment, panels, flashings, drainage interfaces, access, protection and cleanup. Put each bidder in a separate column. Mark an unanswered item as unknown rather than assuming it is included. This makes a lower price easier to interpret and gives every contractor a chance to clarify the same questions.
Resolve allowances before choosing
For example, one quotation may include a stated allowance for deck repairs while another excludes them entirely. Ask how any additional work is documented, priced and approved. Also ask what changes if the proposed colour or profile is unavailable. A useful clarification becomes part of the written scope; a friendly verbal assurance is harder to compare. Keep the final product selection, exclusions and change process with the accepted proposal.