A change order is a written amendment to a signed roofing contract that adds, removes or changes work and states the price and schedule effect. On a roof replacement, a trigger can be something found once the old shingles are off, such as damaged decking. A good bid says how that will be priced before you sign.
What is a change order on a roof replacement?
A change order is a written record that the contract has changed: work added, removed or swapped, with the new price and any effect on the schedule. Both sides sign it before the extra work starts. On a roof, one cause is a condition nobody could see until the old roofing came off.
Change orders also cover choices you make, such as a different shingle or an added skylight. This page is about the other kind, the surprise in the structure, because that is where the wording of a bid counts. It is general information, not legal advice. For what your own contract means, ask a lawyer.
Why does a roofer find damage only after the old roof is off?
Because the deck sits under the shingles and the underlayment. An article in Professional Roofing, the magazine of the National Roofing Contractors Association (NRCA), says that looking at a deck’s underside “may not reflect the extent of degradation that may exist on the top surface of the roof deck.” Part of a replacement is the chance to look at the deck itself.
The Asphalt Roofing Manufacturers Association (ARMA) describes how building codes define roof replacement: removing the existing roof covering, repairing any damaged substrate, and installing a new roof covering. It lists the opportunity to inspect the deck and repair any damage among the benefits of replacement over covering the old shingles.
The 2018 International Residential Code, a model code, says that roof replacement “shall include the removal of existing layers of roof coverings down to the roof deck” (the code lists an exception), and that asphalt shingles “shall be fastened to solidly sheathed decks.” Local governments adopt and amend model codes, so ask your local building office what applies to your roof.
Which hidden items can turn into a change order?
A roof bid can leave four things open until the old roof is off: the deck, the drip edge and fascia, the flashing, and the ventilation. The table gives what published sources say about each and a question to put to every roofer. If a bid does not answer a question, it is silent on that item.
| Item | What the sources say | What to ask |
|---|---|---|
| Decking or sheathing | A Malarkey technical bulletin on board decks says “Deteriorated or rotted boards should be replaced.” ARMA says rotted or warped wood, or gaps greater than ¼ inch between deck boards, mean the old shingles will likely need to come off, and that rotten, warped or otherwise damaged boards “must be replaced before applying new shingles.” The Professional Roofing article says a degraded deck’s fastener holding and load capacities can be reduced significantly. | What is the price for each sheet of deck replaced, and for a board deck, each board or foot? |
| Drip edge and fascia | The model code says a drip edge “shall be provided at eaves and rake edges of shingle roofs.” The fascia is the board along the eave edge. The sources on file do not give a rule for fascia repair. | Is new drip edge in the bid, and how is a rotted fascia board priced if one turns up? |
| Flashing | The model code says base and cap flashing “shall be installed in accordance with manufacturer’s instructions.” | Which flashings are replaced and which are reused, and what happens if a reused one fails inspection? |
| Attic ventilation | ARMA says a reroofing process should include an evaluation of whether existing attic ventilation is adequate. Owens Corning’s instructions say ventilation must comply with local building codes. | Does the bid include a ventilation check, and how is added ventilation priced if it falls short? |
What do shingle makers say about the deck under the shingles?
Shingle makers write deck condition into their installation instructions. Owens Corning’s instructions for its Duration series describe shingles designed for “any properly built and supported wood roof deck having adequate nail holding capacity and a smooth surface.” Ask each roofer how the bid treats a deck that does not fit that description.
- Warranty. Malarkey says failing to correct deck problems such as gaps of ¼ inch and greater, or warped, split, cracked, deteriorated or rotted boards, “may void your warranty.” Ask each roofer which shingle maker’s instructions the bid follows.
- A wet deck. Owens Corning says the installer must “Prevent the wood deck from getting wet before, during and after installation.” Ask how the open deck is protected at the end of each day.
- Not every sheet. APA, The Engineered Wood Association, said in an answer relayed by West Fraser that in general it saw “no reason to arbitrarily replace roof-sheathing panels” during roofing replacement, and that the decision belongs to “a qualified professional” with direct knowledge of the job. A bid should not assume every sheet is replaced, or none.
How does a well-written bid handle unknowns up front?
It names the unknown and prices it before you sign. That can be a unit price, such as a set price for each sheet of decking replaced, or a stated allowance for decking, plus a rule that no extra work starts without your written approval and photos of what was found. A surprise then becomes a quantity times a price you already saw.
- Unit price. A price for each sheet of plywood or OSB deck replaced. For an older board deck, which Malarkey describes, the unit may be each board or each foot. The bid should say which unit applies.
- Stated allowance. A set sum in the bid for deck repair, with the bid saying what happens if less is used (a credit to you, or not) and what happens if more is needed.
- Written approval. A signed change order before the extra work, naming the location, the quantity, the unit price, the total and any change to the schedule.
- Photos. Dated photos or video of each damaged area before it is covered or replaced, with the location noted, sent to you. Do not climb onto the roof yourself to check.
- Who decides. Who judges that a sheet is rotted and not sound, and how you reach each other the day it happens.
- Schedule. Whether added deck work moves the finish date. Our guide on how long a roof replacement takes covers the phases.
What should a change order itself say?
A change order should say what was found, where, what work will change, the quantity and unit price, the new total, any effect on the schedule, how it is paid, and which contract it amends. Both parties sign it before the work. If a document asks for your signature and leaves any of these blank, ask for them first.
How does comparing bids on one scope make unit prices comparable?
When every contractor prices the same written scope, you can set each bid’s decking terms side by side: unit price, allowance, approval rule. Without a shared scope, one bid may say nothing about decking, another may carry an allowance and a third a price per sheet, and the totals hide those differences.
| What the bid says about decking | What you still need to find out |
|---|---|
| Nothing | Whether deck repair is excluded, included, or left for a change order, and at what price. |
| An allowance | How much deck the allowance covers, and what happens to any amount left over or any shortfall. |
| A unit price | The unit (sheet, board or foot), whether labor is in it, and who approves each use. |
A unit price lets you compare two bids on the same footing even though nobody knows how much deck is bad. Our side-by-side worksheet for roofing bids works with this: add a row for decking and fill it in for each bid.
What should I ask every roofer about hidden damage?
Send the same questions to every bidder and ask for written answers:
- Does the bid include any deck replacement, and if so how much?
- What is the price for each sheet of deck replaced, and for each board or foot of board deck?
- Is there an allowance, and what happens to the unused part or a shortfall?
- Will you get my written approval, with photos, before any extra work starts?
- How are drip edge, fascia, flashing and ventilation handled if they need work?
- Which shingle maker’s installation instructions does the bid follow?
- How do you protect the open deck at the end of each day?
- Does extra work change the finish date, and how will you tell me?
The same unknowns also show up as lines in a bid itself. Our guide to reading a roofing contractor estimate goes line by line.
Where Otter Quotes fits
Otter Quotes creates a written scope of work for your project and sends it to multiple contractors. Every bid is on the same scope and the same measurements, so you can ask each contractor to state how it handles unknowns such as decking, and compare the answers side by side. You compare the bids online, next to reviews and licensing information, without a salesperson visiting your home.
Because contractors know they are competing, they are more likely to include better materials and warranties. Otter Quotes is not a contractor, does not sell upgrades and does not work with your insurance company. Contractors pay Otter Quotes a fee on the accepted bid.
Frequently asked questions
What is a change order on a roof replacement?
A change order is a written amendment to a signed roofing contract. It records work that is added, removed or changed, along with the new price and any effect on the schedule. On a roof replacement it can be used when something is found after the old roof comes off, such as damaged decking. Both parties sign it before the extra work starts.
Can a roofer charge extra if rotted decking is found?
That depends on what your contract says, so read it before you sign. A bid that already states a price for each sheet of decking, or an allowance, turns the surprise into a number you saw in advance. Ask for those terms, a written change order and photos before extra work starts. For what your contract means, ask a lawyer.
How can I know the cost of rotted decking before work starts?
You cannot know how much deck is bad until the old roofing is off. You can know the price per unit. Ask each roofer to put in writing a price for each sheet of deck replaced, or a stated allowance, and what happens to any amount left over. Then extra deck is a quantity times a price you already compared.
Why did the first estimate not show the damage?
The deck is under the shingles and the underlayment. An article in NRCA’s magazine says a look at a deck’s underside may not reflect the extent of degradation on its top surface. The deck can be checked once the old covering is removed. That is why a bid should say, before you sign, how deck repair will be priced.
What should a roofing change order include?
It should say what was found and where, what work changes, the quantity and unit price, the new total, any effect on the schedule, how it is paid, and which contract it amends. Ask for photos of the damaged area. Both parties sign before the work starts. If any item is blank, ask for it first.
Sources
- Malarkey Roofing Products, Technical Bulletin: Wood Board Decks as a Substrate for Steep Slope Roofing, April 2023.
- Owens Corning Roofing, Duration Series Shingles Installation Instructions, July 2026 edition.
- Asphalt Roofing Manufacturers Association, Asphalt Shingle Reroofing: Replacement vs. Recover, February 2024.
- Tom Bollnow and Joan P. Crowe, AIA, Professional Roofing (NRCA), Steep-slope reroofing considerations, August 2004. An older article; check current NRCA guidance.
- International Code Council, International Residential Code 2018, Chapter 9, Roof Assemblies, sections R905.2.1, R905.2.8.1, R905.2.8.5 and R908.3. Local adoptions may amend the model text.
- West Fraser, Does Reshingling Damage Roof Sheathing?, October 12, 2016, relaying an answer from APA, The Engineered Wood Association.