“We found rotten decking” is sometimes an honest discovery mid-tear-off and sometimes a way to pad the bill once your roof is already open. Here is how to tell the difference.
It is one of the most common calls a Calgary homeowner gets mid-project: the crew has torn off the old shingles and found soft, rotted, or delaminated plywood underneath, and now the job costs more than the signed quote. Sometimes this is completely legitimate. Decking rot is real, common on older homes, and genuinely cannot always be seen until the shingles are off.
It is also, occasionally, a way for a less scrupulous contractor to pad a job once you have no real leverage: your roof is open, winter or rain is a real risk, and you are not in a position to shop around mid-tear-off. This guide explains what decking damage actually looks like, why it happens, and how to know whether the surprise you are being told about is genuine.
Why decking fails in the first place
Roof decking, plywood or oriented strand board nailed to the rafters, rots or delaminates from sustained moisture exposure. The most common causes on Calgary homes are long-standing minor roof leaks that went unnoticed, poor attic ventilation that traps humid air against the underside of the deck, ice damming at the eaves that backs water up under old shingles, and age-related wear on homes original decking that has simply been there since the house was built decades ago.
None of these causes are visible from a rooftop inspection before tear-off. A pre-project inspection can flag warning signs, soft spots detectable by walking the roof, sagging areas, interior ceiling stains, but the full extent of decking damage is genuinely only confirmed once the old shingles and underlayment come off.
What a fair decking discovery actually looks like
A legitimate discovery comes with photos taken in the moment, before any new decking goes down, showing the specific damaged sheets in place on your roof. The crew or foreman should be able to point to visible rot, delamination (layers separating), or a soft spot you can press with a boot, not just claim damage exists.
The pricing should match whatever per-sheet rate was already written into your contract before the tear-off began. If your quote included a stated per-sheet decking price, the surprise should only be about how many sheets, not what each one costs. A contractor who quotes a new, higher per-sheet price only after your roof is open has changed the terms at the worst possible moment for you to negotiate.
Red flags that suggest padding, not genuine damage
Some patterns are worth pushing back on hard. A crew that claims a large percentage of decking needs replacement with no photos and no willingness to show you the specific sheets is asking you to trust a number you cannot verify. A contractor who never mentioned decking as a possibility during the original quote, despite an older home with visible interior signs of past leaks, may not have inspected carefully or may be treating decking replacement as a built-in upsell.
Pressure to decide immediately, without time to review photos or call a second opinion, is itself a warning sign. A legitimate contractor understands that a decking overage is a real cost to you and will give you a reasonable window, even if short, to review evidence before authorizing the extra spend.
Protecting yourself before the tear-off starts
The best defense against a decking dispute happens before the crew ever shows up. A written contract with a firm, stated per-sheet decking replacement price removes the biggest variable that lets a bad actor exploit the situation. Ask the contractor to commit to photographing any damaged decking in place before removal and to text or email you those photos in real time, not after the job is finished.
For an older home, or one with a history of past leaks or attic ventilation issues, budgeting a contingency of 5 to 15 percent above the base quote for possible decking replacement is a reasonable, honest planning step, rather than assuming your quote’s base price will be the final number.
- Confirm a per-sheet decking price is written into the contract before tear-off.
- Ask for real-time photos of any damaged decking found, before removal.
- Compare the claimed damage percentage against your home’s age and leak history.
- Request time to review evidence before authorizing significant extra cost.
- Budget a reasonable contingency for older homes rather than assuming zero overage.
- Get the final decking sheet count and cost itemized on the closing invoice.
What a reasonable overage actually costs
Decking replacement is priced per 4×8 sheet, and most homes that do need replacement need a handful of sheets, not a full deck rebuild. A full decking replacement across an entire average roof is uncommon outside genuinely old or long-neglected homes; when a contractor claims the entire deck needs replacing, that is a moment to ask more questions, get a second opinion if the roof is still tarped and stable enough to wait, or at minimum request very clear photographic justification before agreeing.
How much decking replacement typically adds to a project
Decking is priced per 4×8 sheet, and most homes needing any replacement at all need somewhere between a handful and a few dozen sheets, not a full deck rebuild. On an average single-detached home, discovering that a modest portion of the deck needs replacing is common and should shift the total by a predictable, pre-agreed amount rather than a dramatic one, if the per-sheet price was locked in before tear-off as it should be.
A claim that the entire deck needs replacing is the outlier, not the norm, and it is worth treating as a moment to slow down rather than sign off immediately. Ask to see the full extent of the damage yourself if the roof is stable enough to allow it, or request a second, independent opinion before authorizing a full deck rebuild on a home that did not show obvious signs of that level of damage beforehand.
What to do if you think you were overcharged after the fact
If a project is already finished and you suspect the decking charge was inflated or the damage was not real, start by requesting the photos the crew should have taken during tear-off. A contractor who cannot produce timestamped photos of the specific damaged sheets has a weaker position than one who can show you exactly what they found and replaced.
From there, a second contractor can sometimes assess whether the decking that was replaced shows visible evidence of having actually been necessary, though this becomes harder to verify definitively once new decking and shingles are already installed over it. This is exactly why getting the documentation in real time, before you approve the extra cost, matters far more than trying to reconstruct the truth afterward.
Why older homes carry more decking risk from the start
Homes built before roughly the 1990s in some Calgary neighbourhoods more commonly used thinner or lower-grade sheathing than current building practices call for, and decades of small ventilation and moisture issues have had more time to compound. This does not mean every older home needs decking replacement; it means the odds are genuinely higher, and budgeting a contingency is more reasonable on an older home than on one built in the last decade.
If you are buying an older home and a re-roof is on the horizon, ask the current owner whether the attic has ever shown moisture staining or ventilation issues, and treat a re-roof quote on that home as a candidate for the higher end of a reasonable decking contingency range.
A final sanity check before you approve extra cost
If the total decking overage feels disproportionate to the roof’s visible age and history, trust that instinct enough to ask one more round of questions before signing off. A brief pause costs you nothing; an unnecessary charge you approved under pressure is harder to undo.
Real decking damage should be provable, not just claimed
Rot happens, and it is a genuine, common part of Calgary re-roofing that a fair contractor discloses honestly with a price you already agreed to ahead of time. The line between an honest discovery and an upsell is documentation: photos, a pre-agreed price, and a reasonable window to review before you say yes.
Before your next re-roof, ask your contractor directly how they handle decking replacement pricing, and learn how to read your Calgary roof inspection report so any decking claim matches what’s actually documented there. If something about a mid-project decking claim feels off, it is worth reviewing the roofing mistakes worth watching for before you approve the extra spend.
About the author: this article was contributed by Angel’s Roofing, a Calgary residential roofing contractor that photographs and documents decking conditions in real time during every tear-off. Decking replacement is priced per sheet in the original written contract, never negotiated after the roof is open.
