Most of the gap between bids isn’t profit margin — **it’s scope**. Two estimates for the same roof can differ by thousands because they aren’t quoting the same work.
The line items that usually explain the difference:
– **Tear-off vs. overlay.** Nailing new shingles over the old layer is cheaper today and costs you years of roof life.
– **Decking allowance.** A bid with no per-sheet price for rotted plywood isn’t cheaper, it’s incomplete. That cost arrives mid-job as a change order.
– **New flashing vs. reused.** Reusing old flashing around chimneys and walls saves a few hundred dollars and is where most future leaks start.
– **Ventilation.** Bringing intake and exhaust up to code is real work that some bids simply omit.
– **Underlayment grade.** Synthetic versus felt, and whether ice-and-water shield is used in the valleys.
– **Warranty tier.** A 2-year workmanship warranty and a 10-year one carry different labor costs.
Ask each contractor to price the same scope. When the scope matches, the numbers usually converge — and the remaining difference tells you something real.