Roof decking — the sheathing that roofing materials attach to — is concealed until the old roof comes off. That makes it the most common source of surprise cost in a roof replacement, and the part of a proposal most worth reading carefully.
What the Crew Checks at Tear-Off
After removal, the deck is checked for rot, delamination, soft areas, previous patchwork and attachment condition. Localized damage is normal on older Seattle-area roofs, especially near valleys, penetrations and roof edges. See roof deck and sheathing repair.
How Honest Proposals Price It
Because the extent of damage is unknown before tear-off, a defensible proposal states a unit price or documented procedure for replacing damaged sheathing — typically handled through a written change order with photos — rather than pretending no decking will ever need replacement.
When Decking Affects Permits
Some jurisdictions treat sheathing replacement differently from surface-only reroofing. Bellevue, for example, identifies sheathing changes in its permit guidance. Check the roofing permits page and the authority for the project address.