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What does dry rot or decking repair add to a roof replacement in the North Bay?

Short answerDecking repair is the most common surprise in a North Bay reroof, because rot and spaced boards only show once the old roof is off. It can add anything from a few sheets to a full new deck. Ask for a per-sheet price in the contract, then get a free written estimate for your roof.

Every roofer we work with is licensed, insured and highly reviewed by Bay Area homeowners.

Updated · Sources reviewed November 12, 2026 · By North Bay Roof Replacement

  • Active C-39 roofing license, checked on CSLB
  • Contractor's bond and workers' comp on file
  • Tear-off, permit and warranty paperwork handled
  • Free written estimate, no obligation

What is roof decking, and what is dry rot?

The deck, or sheathing, is the layer of plywood, OSB or boards the roofing is nailed to. Dry rot is fungal decay in wood that has stayed damp; it leaves sheathing soft, crumbly or delaminated. Spaced sheathing, also called skip sheathing, is boards laid with gaps, common under old wood shake roofs.

What does the code require under a new roof?

California's Residential Code requires asphalt shingles to be fastened to wood structural panels or solid lumber sheathing (CRC R905.2.1), so spaced boards need plywood or OSB over or in place of them before shingles go on. Rotten sheathing has to be replaced because it won't hold nails.

What are the signs of decking problems before tear-off?

  • Sagging between rafters seen from the street
  • Soft or spongy spots underfoot (a roofer's observation)
  • Dark stains or daylight on the underside of the deck in the attic
  • Long-running leaks at the same spot

How is decking priced in a contract?

Ask every bidder to state a unit price for replacement decking, per sheet or per square foot, and to show you photos of what they replace. California requires extra work and change orders on a home improvement contract to be in writing (B&P 7159.6). For your actual price, request a free written estimate: a licensed roofer measures the roof and prices your exact scope.

Where does decking rot show up in the North Bay?

In Sonoma and Napa, the classic decking issue is the shake-to-Class-A conversion: older country and ranch homes with wood shake are usually sheathed with spaced boards, which shingles and many other Class A roofs can't go over. West county homes near Sebastopol, Guerneville and the Russian River add fog, shade and redwood litter, which bring rot. In unincorporated Sonoma County, Permit Sonoma requires a pre-inspection before the new roof goes on, and decking work fits around it.

Related: what drives roof replacement cost, roof size estimator, repair or replace, quote checker.

Every roofer we work with is licensed, insured and highly reviewed by Bay Area homeowners.

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Frequently asked questions

How much decking will my roof need?

No one knows until the old roof is off. A good bid states a unit price so the extra is predictable.

Can a roofer just roof over soft spots?

No. New roofing needs a sound deck to hold fasteners; rotten sheathing should be replaced.

Why does my shake roof replacement include new sheathing?

Shake is often on spaced boards. The code requires asphalt shingles to go on structural panels or solid sheathing, so roofers add plywood or OSB over or in place of the boards.

Related questions

Sources

Sources reviewed November 12, 2026. Figures are published estimates and official fees, not quotes. Confirm prices, permits and requirements with your contractor and building department. This page is general information, not legal or insurance advice.