Aerial drone view of a tree-lined residential neighbourhood in Ontario, representing real estate transactions and latent defect disputes in Ontario property law
Date: June 10, 2026

Latent Defects in Ontario Real Estate: What Buyers and Sellers Need to Know

Discovering a significant hidden flaw in a property after closing is one of the most stressful situations a buyer can face. Whether it is mold concealed behind drywall, a leaking foundation that only becomes apparent in wet weather, or faulty wiring hidden from view, the question of who bears responsibility turns on a specific legal distinction: whether the defect was latent or patent, and whether the seller knew about it.

Ontario law on latent defects sits at the intersection of property law, contract law, and negligence. This article explains what a latent defect is, how courts distinguish it from a patent defect, what obligations sellers and builders carry, and what options are available to buyers who discover hidden problems after the deal has closed. For an overview of how real estate disputes are handled in Ontario, see our practice area page.

The core distinction
A latent defect is a hidden flaw not discoverable through a reasonable inspection. A patent defect is visible and would be found by a reasonably attentive buyer. Sellers may be liable for concealing known latent defects that affect safety or habitability. Buyers generally bear the risk of patent defects they failed to notice.

The seller's knowledge is the central issue in latent defect claims. A seller who genuinely did not know about the defect is in a fundamentally different legal position from one who knew and said nothing. Ontario courts focus on what the seller knew, what they disclosed, and whether their conduct constituted active concealment or misrepresentation.

Latent defects vs patent defects: the legal distinction

The distinction between latent and patent defects determines who bears the risk of a property problem discovered after closing.

Latent defects

  • Hidden and not discoverable through a reasonable inspection
  • Often involve concealed structural, water, or electrical problems
  • Seller may be liable if they knew and failed to disclose
  • As-is clauses do not protect sellers who actively concealed them
  • Limitation period runs from discovery, not from closing
  • Can give rise to claims against builders by subsequent purchasers

Patent defects

  • Visible and discoverable through ordinary inspection
  • Governed by caveat emptor: buyer beware
  • Risk generally rests with buyer who failed to notice
  • Home inspection is the primary protection for buyers
  • Seller not liable for patent defects the buyer chose to accept
  • Waiving inspection does not convert patent defects to latent ones

Common examples of latent defects in Ontario real estate

  • Hidden water damage, mold, or rot concealed behind walls, ceilings, or finishes
  • Foundation cracks covered by drywall, flooring, or applied finishes
  • Basement or crawl space leaks that only manifest in wet weather or spring thaw
  • Faulty or outdated electrical wiring concealed within walls
  • Plumbing defects hidden within finished ceilings or walls
  • Pest or rodent infestations in inaccessible areas
  • Previous fire or flood damage concealed by renovations
  • Soil contamination or environmental issues not apparent from a visual inspection

Seller disclosure obligations in Ontario

Ontario sellers are not required to disclose every imperfection in their property. The common law principle of caveat emptor, buyer beware, places significant responsibility on buyers to investigate the property before closing. However, caveat emptor has important limits that protect buyers from concealed defects.

Sellers in Ontario must disclose latent defects that they are aware of where those defects affect the safety or habitability of the property. Failure to disclose, or making misrepresentations about the property's condition, can expose the seller to claims for fraudulent or negligent misrepresentation, breach of contract, or breach of the duty to disclose depending on the specific facts.

The seller's actual knowledge is the central question. A seller who genuinely did not know about a latent defect is in a different legal position from one who knew and concealed it. Active concealment, such as painting over mold or installing new flooring over a damaged subfloor to hide a defect, is treated more seriously by courts than innocent non-disclosure of an unknown defect.

An as-is clause in a real estate agreement shifts the risk of patent defects to the buyer but does not protect a seller who has actively concealed a known latent defect or made misrepresentations about the property's condition. Ontario courts have consistently held that as-is language cannot be used as a shield against liability for deliberate non-disclosure of known defects affecting safety or habitability.

What Ontario courts have decided: key cases

Bolduc v. Legault, 2023 ONSC 1192

The Ontario Superior Court held that a seller who conceals a latent defect affecting the safety or habitability of the property may be liable to the buyer where it can be proven that the seller had actual knowledge of the defect. The decision reinforces that knowledge and deliberate non-disclosure, rather than mere failure to discover the defect, are the foundations of seller liability in latent defect cases.

The case is a recent and direct statement of the principle that seller liability in latent defect claims turns on what the seller knew, not simply on whether the defect existed. A seller who took reasonable steps to investigate and disclose, and who genuinely did not know about the defect, is in a substantially different legal position from one who knew and said nothing.

Mariani v. Lemstra, 2004 ONCA

The Ontario Court of Appeal confirmed that builders and developers owe a duty of care to successive purchasers of property in respect of latent defects that make the property dangerous or unfit for habitation. The duty is not limited to the original buyer: a subsequent purchaser who was not the original party to the building contract can still bring a claim against the builder for latent construction defects.

This decision is particularly significant for condominium and new construction disputes, where buyers may be several steps removed from the original construction relationship. The builder's duty of care to ensure that properties are free of dangerous latent defects survives resale and flows to subsequent purchasers who discover the defect after they have acquired the property.

Discovered a hidden defect after closing on an Ontario property?

The two-year limitation period runs from discovery, but acting quickly matters. Evidence needs to be preserved, the defect needs to be documented, and the seller's knowledge needs to be investigated before it becomes harder to establish. Get legal advice now, not after repairs are complete.

Call: 1-800-771-7882 Find Out If You Have a Claim

Buyer protections and what you need to establish

If you discover a latent defect after closing on an Ontario property, you may have a legal claim against the seller or builder. To succeed, you generally need to establish the following elements.

The defect was latent, not patent

You must show that the defect was not discoverable through a reasonable inspection. If a competent home inspector exercising ordinary skill should have found the problem, the defect may be characterized as patent rather than latent, and caveat emptor may apply. Documenting that the defect was genuinely hidden, including evidence of how it was concealed, is important to establishing this element.

The defect affects safety or habitability

Not every hidden imperfection gives rise to a legal claim. Ontario courts focus on latent defects that affect the safety or habitability of the property in a meaningful way. A defect that creates a health risk, renders part of the property unusable, or significantly affects structural integrity is more likely to ground a successful claim than a minor cosmetic issue that happened not to be visible.

The seller knew about the defect

Seller knowledge is the central element of most latent defect claims. You need evidence that the seller was aware of the defect before closing, whether from prior repairs, inspection reports, insurance claims, or direct awareness of the problem. Active concealment, such as fresh paint over a water-stained wall or new flooring installed over a damaged subfloor, can itself be evidence of knowledge.

You acted within the limitation period

The basic limitation period under Ontario's Limitations Act, 2002 is two years from the date you discovered, or ought reasonably to have discovered, the defect and its connection to the seller's conduct. The discoverability rule means the clock starts from knowledge, not from closing. But the clock does run and waiting to seek advice reduces your options.

New home warranties and Tarion protections

Buyers of new homes in Ontario have access to statutory warranty protections through the Tarion Warranty Corporation in addition to their common law rights. The Ontario New Home Warranties Plan Act requires builders of new homes to provide warranties covering defects in workmanship and materials, structural defects, and violations of the Ontario Building Code. These warranties cover different periods depending on the type of defect and provide a claims mechanism that operates separately from court proceedings.

Buyers of new condominiums have additional protections under the Condominium Act, 1998, which governs warranty obligations for common elements and units. Where a latent defect involves a common element, the condominium corporation may be the appropriate party to bring the warranty claim rather than individual unit owners.

For properties not covered by the Tarion program, including resale homes and older properties, common law rights provide the primary avenue for latent defect claims.

Dealing with a latent defect dispute in Ontario, whether as a buyer, seller, or builder?

Latent defect claims require careful analysis of the seller's knowledge, the nature of the defect, and the applicable limitation period. Get advice on your specific situation before taking the next step.

Get Advice on Your Real Estate Dispute Or call us: 1-800-771-7882

Practical takeaways

Latent defects are hidden flaws not discoverable through a reasonable inspection. Patent defects are visible and fall under caveat emptor: the buyer generally bears the risk of defects they could have found but did not.
Sellers in Ontario must disclose known latent defects that affect the safety or habitability of the property. The seller's actual knowledge, not merely whether the defect existed, is the central question in determining liability.
As-is clauses do not protect sellers who have actively concealed known latent defects or made misrepresentations about the property's condition. Courts have consistently held that deliberate non-disclosure cannot be shielded by as-is language.
Builders owe a duty of care to successive purchasers for latent defects that make property dangerous or unfit for habitation, confirmed in Mariani v. Lemstra, 2004 ONCA. This duty survives resale.
The limitation period is two years from discovery under Ontario's Limitations Act, 2002. Preserve evidence, document the defect thoroughly, and seek legal advice immediately after discovering a hidden problem.
Buyers of new homes have access to Tarion statutory warranty protections in addition to common law rights. The appropriate claim mechanism depends on whether the property is new construction and the type of defect involved.

Frequently asked questions

What is a latent defect in Ontario real estate?

A latent defect is a hidden flaw in a property that cannot be discovered through a normal inspection conducted by a reasonably competent buyer. Examples include hidden water damage or mold behind walls, concealed foundation cracks, basement leaks not apparent in dry weather, and faulty wiring not visible during inspection. Latent defects are distinguished from patent defects, which are visible and would be found by a reasonable buyer exercising ordinary care.

What is the difference between a latent defect and a patent defect?

Patent defects are visible and fall under caveat emptor: the buyer generally bears the risk of defects they could have found but did not. Latent defects are concealed and not discoverable through a reasonable inspection. Sellers who know of a latent defect that affects safety or habitability and fail to disclose it may be liable to the buyer regardless of caveat emptor.

Are sellers in Ontario required to disclose latent defects?

Yes, in certain circumstances. Sellers must disclose known latent defects that affect the safety or habitability of the property. Concealing a known defect of this type, or making misleading statements about the property's condition, can expose the seller to claims for misrepresentation or breach of the duty to disclose. The seller's knowledge of the defect is central to whether liability arises.

Can a buyer sue a builder for latent defects in Ontario?

Yes. Ontario courts have confirmed in Mariani v. Lemstra, 2004 ONCA, that builders and developers owe a duty of care to successive purchasers for latent defects that make property dangerous or unfit for habitation. This duty survives resale. Buyers of new homes also have access to Tarion statutory warranty protections under the Ontario New Home Warranties Plan Act.

How long do you have to bring a latent defect claim in Ontario?

The basic limitation period under Ontario's Limitations Act, 2002 is two years from the date the defect was discovered or ought reasonably to have been discovered. The discoverability rule means the clock starts from knowledge, not from closing. If you discover a latent defect after closing, seek legal advice immediately to preserve your rights and evidence.

Does an as-is clause protect a seller from latent defect claims in Ontario?

Not necessarily. An as-is clause shifts the risk of patent defects to the buyer but does not protect a seller who has actively concealed a known latent defect or made misrepresentations about the property's condition. Courts have consistently held that as-is clauses cannot shield a seller from liability for deliberate non-disclosure of known latent defects affecting safety or habitability.

Discovered a hidden defect in an Ontario property after closing? Tell us what's happening.

Whether you are a buyer who has discovered a latent defect, a seller facing a claim, or a builder responding to a warranty demand, Achkar Law advises on real estate disputes across Ontario. We will assess your position honestly and advise on the strongest available approach before the limitation period narrows your options.

Call us at 1-800-771-7882 or fill out the form below and we will be in touch.