- Ontario's basic limitation period gives you two years to start most civil claims, as of mid-2026 (verify the current period before relying on it, since limitation rules can change).
- Discovery isn't about the exact moment something technically went wrong — it's about when you knew, or a reasonable person in your position should have known, that you'd suffered a loss…
- Take water infiltration behind a finished wall.
Some construction problems show up right away — a door that doesn't close, a crack that appears within weeks. Others stay hidden for years: water infiltration behind a wall, a structural issue under a finished floor, a defect that only becomes obvious once it has caused real damage. When a problem surfaces years after the work was done, the natural worry is whether it's already too late to do anything about it.
Ontario's limitation period for a construction deficiency claim doesn't necessarily run from the day the work was finished — and understanding when the clock actually starts matters just as much as knowing how long it runs.
The General Rule: Two Years From Discovery
Ontario's basic limitation period gives you two years to start most civil claims, as of mid-2026 (verify the current period before relying on it, since limitation rules can change). Critically, that two years generally doesn't start on the day the underlying work was performed — it starts on the day the claim was "discovered." This discoverability principle is central to how limitation periods work for construction problems in particular, precisely because so many defects aren't obvious right away.
What "Discovered" Means
Discovery isn't about the exact moment something technically went wrong — it's about when you knew, or a reasonable person in your position should have known, that you'd suffered a loss connected to the contractor's work, and that pursuing a claim would be an appropriate response. In practice, that usually means the point at which the problem became apparent enough — through visible symptoms, a professional's opinion, or your own reasonable investigation — that a person in your position would recognize something was genuinely wrong and connect it to the earlier construction work.
How This Plays Out With Hidden Construction Defects
Take water infiltration behind a finished wall. If it isn't visible and produces no symptoms for several years, the limitation clock likely doesn't start running the day the wall was closed up — it more likely starts once staining, odour, or other signs became apparent enough that a reasonable homeowner would investigate and connect the problem back to the earlier work.
This doesn't mean unlimited time, though. Once red flags do appear, courts scrutinize how promptly you acted. A homeowner who notices staining and waits years before investigating further faces a much harder argument about when their claim was actually "discovered" than one who investigates and acts soon after the symptoms appear.
The Outer Limit: Fifteen Years
Even where a problem genuinely wasn't discoverable earlier, Ontario law generally imposes an ultimate limitation period of fifteen years from the act or omission itself, as of mid-2026 (verify the current period before relying on it). This operates as a hard backstop in most circumstances, regardless of when the problem was actually discovered — so a defect that only becomes discoverable after that outer window has closed generally can't support a claim, subject to narrow exceptions that go beyond the scope of a general article like this one.
A Different Clock Entirely: Construction Lien Deadlines
It's worth flagging a common point of confusion. If you're a contractor or supplier who wants to preserve a construction lien against a property for unpaid work, those deadlines are entirely different — measured in weeks, not years, and running from specific statutory trigger dates rather than from discovery. A homeowner pursuing a breach-of-contract claim against a contractor and a contractor trying to preserve a lien against a property are on two completely different clocks, even though both disputes might arise from the same renovation.
What This Means Practically
Even though Ontario law often gives homeowners more time than they assume when a defect is genuinely hidden, that's not a reason to wait once you suspect a problem. Evidence fades, memories become less reliable, and contractors can become harder to locate or may close their businesses entirely. The safest approach is the same one that applies to any deficiency claim: document what you're seeing as soon as you notice it, get a professional opinion if the issue is technical, and get legal advice about timing promptly rather than waiting to see whether it gets worse.
Frequently asked questions
I found a defect five years after the renovation was done — am I out of time?
Not necessarily. If the defect genuinely wasn't discoverable earlier, your two-year clock may only have started once you found it, or reasonably should have, subject to the fifteen-year outer limit. Get advice promptly so a lawyer can assess the specific timeline in your case.
Does the two-year clock start on the day the work was finished?
Generally not — it starts on the day the claim was discovered, which is often, but not always, later than the completion date. In some cases, if the problem was obvious right away, discovery and completion may effectively be the same date.
What's the difference between a lien deadline and a limitation period?
A construction lien has its own short, fixed statutory deadlines aimed at preserving a contractor's or supplier's claim against the property. A limitation period is a separate, much longer window for pursuing an ordinary breach-of-contract claim. They serve different purposes for different parties and shouldn't be confused with each other.
Can I still sue if it's been more than fifteen years since the work was done?
Generally no — the ultimate limitation period acts as a hard outer boundary in most situations, even where discovery came late. There are narrow statutory exceptions that aren't covered in a general article like this one, so get advice on your specific situation before assuming you're out of options.
What should I do the moment I suspect a hidden problem?
Document what you're observing right away, get a professional opinion if the cause isn't obvious, and get legal advice about timing rather than waiting to see if the issue resolves itself or gets worse.
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