Rotted Roof Decking: What Happens to Your Estimate

This page covers re-roofs of pitched roofs on California houses, under California's contract rules as of October 2026, with examples from our jobs in Los Angeles. It doesn't price deck work. The deck is the layer of sheathing the roofing is fastened to, as shown in parts of a roof; the whole job, from the inspection to the final, is in the roof replacement process; the other lines a quote often leaves open, from the tear-off to solar panels, are in hidden costs in a roofing quote.

Once it's found, it has to be dealt with before the new roof goes on. Asphalt shingles have to be fastened to wood structural panels or solid lumber sheathing (CRC R905.2.1), and the Asphalt Roofing Manufacturers Association's manual says a deck that has deteriorated to the point where it won't hold new roofing fasteners, or isn't smooth and structurally sound, should be replaced (ARMA, Residential Asphalt Roofing Manual). California's Energy Code builds the repair into its definition: a roof replacement is "removing the existing roof covering, repairing any damaged substrate, and installing a new roof covering" (section 100.1).

Leaving a soft spot under new shingles moves the risk onto you. ARMA's manual notes that damage to the roofing from deck movement isn't a manufacturing defect of the roofing product, and the warranties agree: GAF's shingle warranty excludes defects in the roof base its products were applied over, and Owens Corning's excludes damage caused by underlying structural conditions and doesn't cover wood decking. What a shingle warranty does cover is in roofing warranties explained.

One kind of new sheathing shouldn't be a surprise at all. The code lets wood shakes and wood shingles go over spaced boards (CRC R905.7.1 and R905.8.1) but not asphalt shingles, so a house going from shakes to shingles can need new sheathing across the whole roof. Spaced boards can usually be seen from an unfinished attic, so that work belongs in the original price rather than in a change order. Which panel, thickness and nailing a new deck takes is in roof decking: plywood vs OSB vs skip sheathing.

Whichever form yours takes, the deck line should name the material. A California home improvement contract has to describe the project and the significant materials to be used (B&P 7159(d)(7)), and a price per sheet means little until you know which sheet. Which panel suits which roof is a separate question from how it's priced.

• Is written and signed by you and the contractor before the work it covers starts. Only then does it become part of the contract (B&P 7159(c)(5) and (d)). The Contractors State License Board (CSLB) puts it plainly: a change in the contract price or the scope "MUST be done with a written 'Change Order,'" signed before the change.
• States the scope: what's being replaced and how much of it. For decking, that's the number of sheets, the panel and where on the roof they go.
• States the amount added to or subtracted from the contract. A change order can take money off as well as add it.
• States its effect on the progress payments or the completion date (B&P 7159.6).
• Carries the subcontractor statement from the contract, if the contractor uses subcontractors (B&P 7159(c)(7)).

The added amount follows the same payment rule as the rest of the contract. Apart from the down payment, which is capped at $1,000 or 10% of the contract price, whichever is less, a contractor can't ask for or accept payment beyond the value of the work performed or the material delivered (B&P 7159.5; contractors that furnish a full performance and payment bond, or an equivalent approved by the CSLB, are exempt). So the money for the deck can't be collected ahead of the plywood arriving or the work being done.

What if the boards were replaced without one? The law says an extra work or change order isn't enforceable against the homeowner unless it sets out the scope, the amount and the effect on the payments or the completion date (B&P 7159.6). That doesn't make the work free: the same section says it doesn't rule out the contractor recovering compensation for work performed through legal or equitable remedies against unjust enrichment, and that you can't require a contractor to do extra work without written authorization. The paper is there to settle the count and the price while the roof is open, not to argue about them afterwards.

• The whole roof. On our 2025 Woodland Hills re-roof, 28 squares of old wood shake came off and the whole roof was re-decked with new plywood: 87 sheets, or 2,784 square feet, about the 28 squares the job was priced on. The re-deck was in the scope from the start; the plywood was ordered with the rest of the material and delivered a day ahead, so the deck could go down first.
• Part of the roof. On a 2023 North Hollywood re-roof of 18 squares of shingle, the rot was priced separately: twelve sheets of half-inch plywood and 170 feet of 1-by-4 fascia board, on the main house only. Twelve sheets is 384 square feet, about a fifth of the shingled roof. The permit was written for a re-roof over new solid sheathing, and it was finaled. Where rot at the roof edge comes from and how far it goes is covered in dry rot in fascia, eaves and roof sheathing.

To check a count you're given, multiply the sheets by 32 to get square feet, divide by 100 to get squares, and compare the result with the squares in your contract. Thirty sheets on a 24-square roof, for example, is 960 square feet, or about 40% of the deck: a share to see in photos, not just on paper. Ask for photos of each area before it's covered, with the count for each; once the underlayment is down, nobody can count the sheets again. Fascia, as on that North Hollywood job, is counted in linear feet, and rot in the rafters themselves is framing repair rather than decking, so it belongs on its own line.

That's how our 2024 Canoga Park re-roof ran. The contract excluded damaged plywood, since nobody could see the deck before tear-off. When the deck needed replacing, a supplemental permit on November 8 rewrote the scope from existing to new sheathing, 17 days after the original permit for 22 squares, and both permits were finaled that November; what else stretches a re-roof's calendar is in how long a roof replacement takes. The permit steps are in getting a roof permit in the City of Los Angeles; other cities and the county have their own routes, covered in re-roof permit rules across LA-area cities.

1. The form. Which of the four ways your contract handles the deck, in writing.
2. The unit price and what it buys. A price per sheet with the panel named, and a price per linear foot for boards and fascia.
3. The allowance, if there is one. How many sheets are included, and whether unused ones come off the price.
4. How you'll be told. Photos of each area, and a written change order with the count, the amount and the effect on payments or the completion date, plus how it will reach you for a signature while the roof is open.
5. The permit. Who files a revised permit if the scope changes from existing to new sheathing, where the agency calls for one.

The rest of what to check in a roofing contract, including the right to cancel one signed at home, is in how to choose a roofing contractor in California. On our jobs, the deck is examined with the roof open, and any real additional work is identified there and agreed with you before it happens; how we run a re-roof is on our roofing page.

Code sections, rules and figures on this page come from the primary sources below. Codes, local requirements and product terms change; each was verified October 9, 2026.

1. California Business and Professions Code, section 7159, home improvement contracts (as amended by SB 517, effective January 1, 2026)
2. California Business and Professions Code, section 7159.5, contract amount, down payment and progress payments
3. California Business and Professions Code, section 7159.6, extra work and change orders
4. Contractors State License Board, What is a contract (home improvement contracts)
5. California Residential Code 2025, Chapter 9, Roof Assemblies (R905.2.1, R905.7.1, R905.8.1, R908.3, R908.4)
6. California Energy Commission, 2025 Building Energy Efficiency Standards (Title 24, Part 6), section 100.1, definition of roof replacement
7. Asphalt Roofing Manufacturers Association, Residential Asphalt Roofing Manual: Design and Application Methods, 2014 edition (deck materials, deck…
8. GAF, Shingle & Accessory Limited Warranty (RESWT160)
9. Owens Corning, Standard Product Limited Lifetime Warranty
10. LADBS, Express Permits (No Plan Check Required), Information Bulletin P/GI 2026-003, revised June 10, 2026