How do I know if my roof decking really needs to be replaced?

Decking is the plywood or OSB under your shingles, and it is the one line item on a roof job that shows up after the roof is already torn open — when you cannot shop it, cannot delay it, and cannot get a second opinion. It is also, often, entirely real. Here is the uncomfortable thing we found while researching this article: there is no credible published figure for how much decking a normal roof needs. So the answer is not a number you can hold your roofer to. It is a short list of things you put in the contract before anyone sets a ladder against your house.

What we went looking for, and did not find

We wanted to open this with what normal looks like — how many sheets an ordinary replacement uses, how often decking gets touched at all. So we checked the shingle manufacturers, the national roofing trade association and its magazine, the building-science publications, the builder magazines, and the insurance research bodies. Not one of them publishes a percentage-of-jobs figure or a sheets-per-job average. Every number in circulation traces back to a single roofing company's blog, offered as that company's own experience, with no method behind it.

And they do not agree with each other. Not by a little.

• HomeHero Roofing, outside Chicago, says that based on its experience over half of full roof replacements need some decking replaced — and it builds two sheets into every quote as a standing allowance.
• Bill Ragan Roofing, in Nashville, says most of the time a few boards have to be replaced and that needing the entire deck redone is uncommon.
• Happy Roofing says most homes require anywhere from 8 to 15 sheets, and that ventilation-driven cases can run 20 to 25 sheets.
• Driftwood Builders Roofing, in Central Texas, puts it at 5 to 15 percent of the deck on a typical re-roof.

A few boards, and eight to fifteen sheets, are both offered as the ordinary case. Nobody reconciles them. That does not make any of these companies wrong — a Chicago roof, a Nashville roof and a Hill Country roof genuinely differ, and each of them is honestly describing what walks through their door. What it means for you is narrower and more useful: you have no benchmark. If a roofer tells you your house needs eleven sheets, there is no published normal to hold that number up against.

You can't check a decking charge against an industry average, because there isn't one. Check it against photographs and a price you agreed to in advance.

About the line that decking lasts 20 to 30 years

You will see that figure repeated across the internet as though it were settled.

It traces to contractor blogs, not to any study we could find. And it points you at the wrong question. Decking does not wear out on a schedule the way shingles do — it fails where something happened to it. Water has been getting in around a valley or a pipe boot. The attic vents badly and condenses moisture on the underside of the sheathing all winter. Two or three layers of old shingles held heat and damp against the wood for years. A forty-year-old deck over a dry, well-vented attic can be perfectly sound. A twelve-year-old deck under a slow leak may be finished. Age alone is a weak predictor, and a roofer pricing decking off your roof's birthday rather than off its condition is guessing.

When the roofer is right, and that happens plenty

Give this part its full weight. The reflex to assume you're being worked is exactly how people end up with an expensive new roof nailed to bad wood.

The residential code requires asphalt shingles to be fastened to a "solidly sheathed" deck, and it sets no percentage threshold anywhere. The test is not how much of the deck is bad. The test is whether what's up there is an acceptable base. The same code requires a roof replacement to come off down to the deck, and does not permit covering over an existing roof where the deck is water-soaked or deteriorated enough that it isn't adequate to build on.

The triggers that genuinely mean a full re-deck

• Spaced or skip sheathing — boards laid with deliberate gaps between them, common on older houses originally roofed in wood shake. Shingles cannot be installed over it.
• Plywood that has delaminated, or OSB that has swollen and gone soft and crumbly along the edges.
• Plank decking with gaps wider than the shingle system tolerates.
• Wood that will no longer hold a nail to the required depth. If fasteners spin, sink through, or pull back out, nothing above them is actually attached to your house.

Manufacturer instructions are their own hard limit, separate from code. Owens Corning, to take one, specifies a minimum 3/8 inch plywood or 7/16 inch OSB, APA-rated; requires the deck to be clean, dry, and free of sagging, rot, delamination and soft spots; and calls for holes or gaps greater than 1/4 inch to be repaired or the boards replaced. Installing shingles over a deck that doesn't meet the spec can void the shingle warranty — so decking you refuse can cost you the warranty you're paying for.

In Florida and on the coast, read this before you accuse anyone

Florida's code requires work on a re-roof that has nothing whatsoever to do with whether your decking is bad. Once the old roof is off down to the sheathing, that sheathing has to be re-nailed — 8d ring-shank nails, six inches on center at panel edges and at intermediate supports — and a secondary water barrier goes over the seams. It's mandatory. Your bill goes up for it even if not one sheet of your decking gets replaced.

Homeowners see a line item about the deck and read it as an upsell. Sometimes it's the state telling your roofer what to do. Ask which one you're looking at, and ask them to point you at the code section. A Florida roofer won't blink at that question, because they get it constantly.

The free checkpoint almost nobody uses

On permitted work, a great many jurisdictions already require a government inspector to look at your bare deck after the tear-off and before anything covers it. Santa Cruz County in California, for example, calls for a tear-off inspection after the old roofing material comes off and before any sheathing is covered, plus a separate inspection of new sheathing before roofing goes over it. Florida re-roofs carry their own deck-nailing inspection.

That inspector doesn't work for you and doesn't work for your contractor, and they are standing on the one surface you will never lay eyes on again. Be clear-eyed about the limit, though. They verify code compliance. They do not adjudicate your invoice, and they will not tell you whether eleven sheets was the honest count — only whether what's up there is a legal base for a roof.

Ask your contractor when the deck inspection is scheduled. Then be home for it.

If your city doesn't inspect, hire your own eyes

That checkpoint only exists where somebody requires it. Plenty of places don't, and unpermitted work has no checkpoint at all by definition. Worse, even where a deck inspection is on the books it can be signed away: Santa Cruz County lets a re-roof certificate be handed over at an in-progress inspection in place of the separate tear-off and sheathing inspections, and cities including Riverside run a formal re-roof self-certification program. The inspection that was going to protect you may simply never happen, and the signaturestanding in for it belongs to the company sending you the bill.

So here is the version that doesn't depend on your city at all. Hire your own inspector to look at the bare deck after the tear-off and before one sheet of wood gets replaced. It is a real move. It also has three practical problems, and anyone who sells it to you without naming them is selling.

It lives or dies on a clause you write before you sign

This is the load-bearing part. Before you sign anything, put a right of access in the contract: you may bring an independent licensed inspector of your choosing onto the property at the deck stage, and no decking is replaced until that inspection happens or you waive it in writing. Ask for it up front and it is a term you negotiated. Ask for it the morning a crew is unloading, and it is a favor you are begging from someone who already priced the job without it.

You own the house, and a contractor generally cannot lock an owner out of their own property — the narrow exceptions are genuine safety risk, a court order, or contract language the owner already agreed to. But your inspector is not you. They are a stranger arriving at an active worksite with an open hole in the roof, and safety is a real and defensible reason to turn a visitor away rather than a dodge. Some construction contracts go further and limit or flatly disallow independent inspections. Read for that language before you sign, because afterward you are asking permission.

It goes in beside the allowance and the per-sheet price in the next section. Same signature, same conversation, one shot at it.

The window is hours, not days

A crew that opens your roof intends to have underlayment over it before they leave, because a bare deck and an afternoon storm is how a roof job becomes a ceiling job. Stripping the old roof off and getting the bare deck covered back up usually happen the same day. Your deck is exposed for part of one morning. So standby cannot mean a phone number you might call — it means your inspector has the tear-off date the day you have it, holds the morning, and gets a text from you when the first shingle comes off. Set up the morning of, it does not happen.

What an inspector will actually do, and what they'll decline

Expect them to stay off the deck. InterNACHI's standards say an inspector is not required to walk any roof surface, and specifically not any roof area that looks unsafe in their own judgment — and a stripped deck somebody has just told you is rotten is the textbook version of that. There is a crew up there working under fall-protection rules at six feet, too, and they do not want an unharnessed visitor in the middle of it. Plan around this rather than argue with it.

• The attic, from underneath. Looking up at the back of the sheathing is where a slow leak or a badly vented attic has been writing its history for years, and it needs nobody on the roof.
• The eave, off a ladder, and the whole roof from the ground with binoculars or a long lens. Not the same as walking it. Still a set of eyes with nothing to sell you.
• Your contractor's own tear-off photographs. If the contract already requires dated photos of every sheet, your inspector reads them instead of climbing anything.
• A moisture meter on the attic side, if they carry one. Ask when you book, not on the day — a home inspection is defined as a non-invasive visual examination, so a meter is something extra you are asking for.

Which points somewhere useful, and this next bit is our recommendation rather than anybody's published guidance. Get the attic looked at before the tear-off, not during it. Nothing about that visit is rushed. Nobody has to stand on anything. It happens while walking away from the bid is still something you can do, and the underside of your sheathing tells you most of what the top side would. Treat the deck-stage visit as the bonus you take if the schedule cooperates, and the pre-tear-off attic look as the one you actually book.

Who to call

• A licensed home inspector, for the attic side. Their standards let the client and the inspector agree on a narrower scope of work before the inspection, so a single-purpose look at your roof sheathing is a normal thing to ask for — put what you want in writing when you book it.
• An independent roof inspector who does not sell or install roofs. The National Roof Certification and Inspection Association keeps a directory, and the entire premise is an inspector with no financial stake in whether you end up buying repairs.
• A licensed structural engineer, when the question has moved from the sheathing to the framing under it. More expensive, and the right call the moment anyone says the word sagging.
• A roof consultant, if you can find one who takes residential work. IIBEC credentials Registered Roof Consultants and Registered Roof Observers, and the observer credential exists precisely to watch a roof go on to spec — but that world runs on commercial and institutional buildings, and a one-day house re-roof is not the job it is built around.

On money, the honest answer is that nobody publishes a standby rate, because nobody productizes standby. We went looking for a named service — re-roof phase inspection, deck verification, anything — and found the role exists on commercial jobs and essentially nowhere in residential. What is published is the ordinary version: the roof-inspection trade association puts a standard roof inspection at $150 to $400, and inspector fee guidance describes consulting hours quoted anywhere from $100 to over $500 an hour depending on the market. A short-notice hold on a morning is a conversation, not a menu price. Ask for the number before you book, the same as you should be asking your roofer.

And the limit, said plainly, because this page has been honest about limits the whole way down. An independent inspector buys you a second opinion. They do not adjudicate your invoice. They can tell you the wood over the northeast corner is soft and that what they could see of the rest looked sound; they cannot tell you whether eleven sheets was the honest count, and they will not settle a billing fight on your behalf. None of this makes a dispute impossible. What it may change is how the job gets priced. A roofer who knows somebody will check the work bids it differently than one who knows nobody ever will. That is our reasoning, not a measured effect, and we would rather say so than dress it up.

Get it into the contract, because afterward you have nothing

1. An itemized decking allowance — how many sheets are already inside the price you're signing. Some companies build in a standing allowance and put it on the estimate.
2. A flat per-sheet price for everything past that allowance, written as a figure and agreed before anyone climbs up. If that rate isn't on paper before the tear-off, it gets set after your roof is open.
3. Dated photographs of each sheet before it's replaced, and a count. This is not a paranoid ask, and it is worth knowing why. On insurance work the carrier already requires it — adjusters are told to get tear-off photos of every sheet, tape measure in frame, before a decking charge gets paid, for the plain reason that once the underlayment and shingles go on, nobody can ever photograph what was underneath again. The people writing the checks worked out on their own that decking is the line item needing proof. You are asking your roofer for exactly what an insurance company would ask for on the same roof, and a contractor who does insurance work already has the habit. Some advertise it: HomeHero photographs the deck once the shingles are off and reviews the images with the homeowner before replacing anything, and NEXGEN says it documents every sheet and won't change scope without talking to you first. That it is a selling point tells you undocumented is the normal state of things.
4. A written, signed change order before the extra work happens and before it reaches your bill.
5. No blank sections anywhere, to be filled in later. Not one.

What the law requires here depends on where you live, and it varies more than people expect. Minnesota requires agreements with a licensed residential roofer, change orders included, to be in writing with a detailed summary of the services and the specific materials. Illinois requires a written contract for home repair work over $1,000. California requires a home improvement contract and any change to it to be in writing and signed before the work that change order covers begins. Other states are quieter about it. Look up your own — and either way, write the requirement into your contract, so it binds your contractor whether or not your legislature already did.

There is no mid-job escape hatch. The three-day right to cancel runs from the day you signed — not from the day the roof came open.

Sit with that one, because it's the sentence that changes behavior. The federal cooling-off rule attaches to the signing event — a sale made at your home — and it runs in business days from that transaction. By the time a crew is standing on your open deck telling you about rot, that window shut weeks ago. There is no cancellation right waiting to rescue you from the conversation you're about to have. Whatever protection you end up with, you bought it before you signed.

If it already happened to you

Say the roof is finished and there's a decking charge on the invoice you never agreed to. You are not out of options, though none of them are fast.

• Ask in writing for the photographs and the sheet count. A company that did the work has them sitting on a phone. A company that didn't, doesn't.
• Line the invoice up against the contract's allowance and per-sheet rate, if you got them in there. This is the entire reason to get them in there.
• If a lien shows up, understand what a lien is for: it secures payment for improvements the owner actually agreed to receive. A contractor generally has to be able to show you agreed to the extra work and to its price, and where a contract requires written change orders, courts have held contractors to that requirement. Talk to a lawyer licensed in your state, quickly — lien deadlines tend to be short and unforgiving.
• Your state's contractor licensing board and your state attorney general's consumer protection office both take complaints, and both are free to file with.

That last one isn't theoretical. In September 2025 the Florida Attorney General sued a Jacksonville roofing company, Florida Roof Specialists, and its president Jeremy S. Rogero under the state's deceptive and unfair trade practices act, after investigating more than 130 consumer complaints. One of the allegations is decking specific: that wood was installed without telling the homeowner, who found out about it from the bill. The state also says the company sued more than 250 of its own customers, and that liens landed on at least 75 homes. These are allegations in a case that is still being litigated, and they describe one company. They are not a description of the trade.

Why the per-sheet price looks so high

A sheet of OSB at the lumberyard costs a small fraction of what an installed sheet costs, and homeowners naturally read that gap as profit. It isn't, or at least it isn't only that. Swapping a sheet mid-tear-off stops the production line: somebody cuts the old sheet out, it gets carried down and hauled away and paid for at the dump, new fasteners go in, and the company carried the material and the crew hours to be standing there at all. The rate you're quoted may be fair or it may not — but you cannot judge it by comparing it to a lumber price. You judge it by getting the rate in writing while your roof is still on, when walking to the next bidder is still something you can do.

Questions people ask next

My roofer says all my plywood is rotten. What should I do?

Ask to see it before any of it comes off — dated photos of the whole deck, or climb up and look yourself if you can do it safely. A full re-deck is a real thing, and skip sheathing, delaminated plywood, or wood that won't hold a nail all genuinely require it. But a full re-deck is also the largest version of this charge, so it earns the most documentation. Ask what specifically disqualifies the deck, ask them to point at the code or manufacturer requirement they're relying on, and ask when the building inspector is coming to look at it.

How many sheets of plywood should a roof replacement need?

There's no published answer, and we looked hard for one. No manufacturer and no trade association puts out a sheets-per-job average; the figures floating around all come from individual roofing companies describing their own work, and they contradict each other badly. Which is why the useful move isn't finding the right number — it's getting an allowance and a per-sheet price into your contract before the roof opens, so whatever the count turns out to be, the price was already settled.

Can I refuse decking replacement and just have my roof shingled?

Not if the decking genuinely doesn't meet the requirement, and this is the honest answer rather than the comfortable one. Asphalt shingles have to go over a solidly sheathed deck, so a roof laid over a deck that fails that test can fail its inspection, and installing over a deck that doesn't meet the manufacturer's spec can void the shingle warranty you're paying for. A reputable contractor may simply decline the job rather than put their name on it. What you can do is require proof: photographs, the specific reason, and the inspector's confirmation.

Should I get a second opinion before agreeing to decking replacement?

Before the roof is open, absolutely — that's when a second opinion is still possible, and it's a good reason to ask every bidder for their per-sheet rate so you can compare those numbers too. Once the tear-off has happened, a second opinion is largely off the table: your roof is exposed, the weather doesn't wait, and nobody else is coming out to bid on a half-finished job. The second opinion has to happen before, which is the whole shape of this problem.

How do I know the decking was actually replaced?

The cheapest check is the one nobody mentions: ask for the lumber delivery ticket. Wood gets delivered to your driveway, and the supplier's ticket says how many sheets showed up, from a company with no stake in your argument. If the invoice bills eleven sheets and the yard delivered four, that is a conversation with a document behind it. You can also count the sheets off the truck yourself, for free, standing in your own driveway. Then the rest: photos with dates, a written count, and the closed permit with its deck or sheathing inspection signed off. New sheets are obvious from the attic too if you can get up there while the work is fresh — clean, unweathered wood against old. Ask for all of it at the time, not weeks later. Once the shingles are down, the evidence is under them.

Written for homeowners by Most Recommended Roofers, which measures which roofers AI assistants actually recommend in 34 U.S. metros. Nobody can pay to be on those lists. How we measure.