The seven-year Major Structural Defect (MSD) warranty is the longest protection a new Ontario home has — and the hardest to claim. Homeowners usually reach for it after something serious has gone wrong: recurring leaks, cracking that keeps growing, a part of the house they can no longer use. Then the builder replies that none of it is a “structural defect,” and the claim stalls.
Most of those denials are not about whether the damage is real. They are about whether the claim has been framed against the actual legal definition, and whether there is engineering evidence to support it. This article covers both.
For homes enrolled after June 30, 2012, Tarion defines a major structural defect as any defect in work or materials — including a crack, distortion or displacement of a structural load-bearing element — that does at least one of the following:
Builders and their consultants often summarise this as three tests — failure, function and use — and a denial letter will usually argue that the claim meets none of them. The important point is the word “or”. A claim only has to satisfy one limb. A defect that has not yet caused a structural element to fail can still qualify if it compromises that element’s long-term capacity, or if it takes a significant part of the home out of normal use.
“Water stains on the garage ceiling” describes a symptom. The definition asks about a defect in work or materials and its effect on a load-bearing element or on the use of the home. Unless the claim connects the visible damage to an underlying cause and to one of the three limbs, it is easy for a builder to characterise it as cosmetic, as maintenance, or as something else entirely.
The MSD warranty expressly does not extend to damage resulting from dampness that does not arise from failure of a structural load-bearing element, from a flood not caused by the builder, or from the acts or omissions of the owner or occupants. Mechanical equipment such as furnaces, air conditioners and heat recovery ventilators is also excluded, as are elevating devices (though not the structure around them).
That is why moisture claims are so often contested. A builder will typically attribute water to weather, ice damming, condensation or occupant behaviour — all of which, if accepted, place the damage outside the warranty. The question that matters is why the water is there and what it is doing to the structure, and that is an engineering question, not a matter of opinion between homeowner and builder.
A plumber can tell you a pipe failed. A contractor can price a repair. Neither can give an opinion on whether a defect affects a structural load-bearing element or the use of a significant portion of the building — and a builder’s response will often say precisely that. When the dispute turns on structural performance, the evidence needs to come from a licensed professional engineer who has inspected the building and can tie each finding to the definition.
When the same kind of failure keeps recurring — several leaks from one system, cracks that reappear after patching, framing that keeps moving — each event on its own can look minor. Presented together, with a common cause identified, they can tell a very different story about whether the use of the home has been materially affected. Building that pattern is part of the investigation.
The goal is not a longer report. It is a report a Tarion representative can follow from observation to conclusion without having to take anyone’s word for it.
The MSD warranty begins on the date of possession and ends on the seventh anniversary of that date. Claims must be made before it expires, and some defects take years to show themselves, so do not wait to see whether a problem “settles”.
Once a claim is filed, the timelines are stricter than for first-year items. For Second-Year and Major Structural Defect forms, Tarion requires that conciliation be requested within 30 days after the end of the initial builder repair period. Missing that window can mean losing the right to have Tarion assess the items at all. If your builder has denied the claim, the time to commission an engineering assessment is before that window opens, not after it closes.
We are independent engineers. We do not act as mediators or as anyone’s legal counsel; we provide the evidence those processes depend on. For MSD claims that means a site investigation, root-cause analysis, a written report framed against Tarion’s definition and the builder’s stated grounds for denial, and attendance at the conciliation inspection where it helps your case. Read more about our Tarion warranty claim support and forensic engineering investigations, or our guide to what happens at a Tarion conciliation.
For homes enrolled after June 30, 2012, a major structural defect is any defect in work or materials, including a crack, distortion or displacement of a structural load-bearing element, that results in failure of a load-bearing element, materially and adversely affects a load-bearing element's ability to carry its loads over its usual service life, or materially and adversely affects the use of a significant portion of the building for ordinary residential purposes. A claim only needs to meet one of these three.
Seven years. It begins on the date of possession and ends on the seventh anniversary of that date.
Not automatically. The MSD warranty excludes damage from dampness that does not arise from failure of a structural load-bearing element, and from floods not caused by the builder. Water-related claims succeed when the evidence connects the water to a structural defect, or shows that it materially affects the use of a significant portion of the home.
For Second-Year and Major Structural Defect forms, conciliation must be requested within 30 days after the end of the initial builder repair period.
When the dispute is whether a defect affects a structural load-bearing element or the use of a significant portion of the home, the evidence carries far more weight coming from a licensed professional engineer who has inspected the building and ties each finding to Tarion's definition.
Send us the denial letter, your warranty forms and a few photos. We will tell you honestly whether the evidence supports the claim, and what an engineering assessment would involve, before the conciliation deadline runs out.
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