A material latent defect is a hidden problem with a property that a buyer could not discover through a reasonable inspection and that meets a legal threshold for significance — making the property unsafe, unfit for habitation, or illegal to use as intended. In Ontario, sellers are legally required to proactively disclose material latent defects to buyers. This is not optional, and it is not waived by an "as is" clause. Understanding what qualifies as a material latent defect, and your legal obligations around it, is essential before you list any Ontario property for sale.

The Two-Part Test: Latent and Material

Not every hidden issue is a material latent defect. The legal concept requires both elements:

Latent: The defect must be hidden — not discoverable by a buyer conducting a reasonable inspection, including a professional home inspection. A crack in the foundation that's visible in the basement is arguably patent (visible). A crack concealed behind finished drywall or a wall covering is latent.

Material: The defect must be significant enough that a reasonable buyer would consider it relevant to their decision to purchase, or to the price they'd pay. Ontario courts and RECO use three specific categories to define materiality:

  1. The defect makes the property dangerous or unsafe to occupy (e.g., compromised structural integrity, asbestos that poses a health risk)
  2. The defect makes the property unfit for habitation (e.g., active flooding that makes the space unlivable)
  3. The defect makes the property illegal to use as a residence (e.g., an illegal basement apartment, an addition without permits that violates zoning bylaws)

Examples of Material Latent Defects

The following conditions have been treated as material latent defects in Ontario real estate transactions and litigation:

  • Foundation cracks allowing water infiltration: A crack behind drywall or under flooring that allows basement flooding is both latent and material — it makes the property unfit for habitation and may be structurally significant.
  • Hidden mould: Mould concealed in wall cavities, behind panelling, or under flooring — especially black mould (Stachybotrys) — is a health hazard. If you know it's there, you must disclose it.
  • Flooding history: A documented pattern of basement flooding, even if remediated, is material. Buyers and their insurers make decisions based on this history. Concealing it creates significant legal exposure.
  • Asbestos-containing materials: Known asbestos in floor tiles, insulation, popcorn ceilings, or pipe wrapping — particularly if friable (easily crumbled and releasing fibres) — must be disclosed.
  • Underground oil tank: A decommissioned or active underground storage tank creates environmental liability. It's latent (underground) and material (significant environmental risk and legal obligation).
  • Structural defects concealed by renovation: A load-bearing wall removed without a permit, or a roof structure weakened by past damage and covered with new sheathing — these are the textbook material latent defect scenario.
  • Pest damage: Active or past termite infestation that has caused structural damage, if hidden by finishes, meets the threshold.
  • Illegal units: A basement apartment that doesn't comply with the Ontario Building Code or municipal zoning makes the property illegal to use in the way it's being represented. This is a material latent defect.

What Is Not a Material Latent Defect

Not every problem rises to the material latent defect threshold:

  • Patent defects: Conditions visible on inspection — peeling paint, aging fixtures, a dated furnace — are not latent. They're observable, and caveat emptor applies.
  • Minor cosmetic issues: Surface damage, worn finishes, and cosmetic conditions don't meet the materiality threshold.
  • Stigmatized property conditions: In Ontario, prior deaths, suicides, or criminal activity on a property are generally not treated as material latent defects unless they resulted in a physical condition (like mould or structural damage). You are not required by law to disclose that someone died on the property.
  • Conditions you genuinely didn't know about: The disclosure obligation is tied to your knowledge. If you genuinely didn't know about a defect, you can't be held liable for failing to disclose it — though courts look critically at claims of ignorance for conditions that attentive owners would have noticed.

If a buyer discovers after closing that you knew about a material latent defect and failed to disclose it, they have several legal remedies available in Ontario:

  • Rescission: The buyer may seek to rescind (undo) the transaction, returning the property to you and receiving their purchase price back. This is the most serious remedy.
  • Damages: The buyer may sue for the cost of remediation, diminished value, and consequential losses (alternative housing costs, carrying costs during remediation).
  • Misrepresentation: If the non-disclosure was fraudulent — you actively concealed a known defect — damages can be substantial and include legal costs.
  • RECO complaint: If your real estate agent knew of the defect and failed to disclose, they face regulatory action from RECO.

Ontario courts have awarded six-figure damages in cases where sellers concealed known material latent defects. The limitation period under Ontario's Limitations Act is generally two years from when the buyer discovered (or reasonably should have discovered) the defect — which may be years after closing, if the defect was truly hidden.

The "As Is" Clause and Material Latent Defects

Selling a property "as is" does not eliminate your obligation to disclose known material latent defects. The "as is" clause shifts responsibility for patent (visible) defects to the buyer. It does not permit concealment of known hidden defects that meet the material latent defect threshold. Ontario courts have consistently held that "as is" clauses cannot be used to excuse non-disclosure of defects the seller knew about and actively concealed.

If you're considering listing "as is" — perhaps for an estate sale or a property with known issues — consult your lawyer about what must still be disclosed and how to frame it in the listing and offer documents. See our guide on what you must disclose when selling in Ontario.

FAQ

Who determines if a defect is "material" enough to require disclosure?

Ultimately, courts make this determination if there's a dispute. The practical standard is: would a reasonable buyer, if they knew about this condition, consider it relevant to their decision to purchase or the price they'd pay? When in doubt, disclose. The cost of disclosure is a negotiated price reduction; the cost of non-disclosure litigation is far higher.

If a defect was professionally remediated, do I still have to disclose it?

Generally yes, if it was a material latent defect. You disclose the history and the remediation — the scope of work, who did it, when, and with what documentation. A disclosed-and-fixed issue is far less damaging to a deal than a disclosed-after-the-fact undisclosed issue. Document remediation thoroughly: keep contractor invoices, warranty documentation, and before/after photos.

Does a home inspection protect me from post-closing claims?

Partially. If an inspector reasonably could have found a defect and noted it in their report, and the buyer received that report, it becomes harder for the buyer to claim the defect was "latent" — it was discoverable. However, a defect hidden in a wall cavity or under concrete is not something a home inspector finds in a standard inspection. The inspector's report does not transfer your disclosure obligation to the buyer's inspector.

What if the defect existed before I bought the property and I inherited it without knowing?

The disclosure obligation applies to what you know. If the defect was present when you purchased and was itself a material latent defect that your seller failed to disclose, you may have a claim against your seller — while still being obligated to disclose what you now know to your buyer. The chain of disclosure obligations runs with knowledge, not with the property's history.

Is a neighbour dispute a material latent defect?

Not a defect in the property itself, but neighbour disputes — particularly those affecting use of the property or involving noise, encroachment, or harassment — are the kind of material facts that RECO requires agents to disclose. Whether it rises to the material latent defect threshold legally is fact-specific. If the dispute affects your use and enjoyment of the property materially, disclosure is the safer path.