Major Structural Defect
MSD
The most serious structural problem in a new Ontario home, covered by Tarion's seven-year warranty from the date of possession.
A major structural defect (MSD) is the most serious category of problem covered by Ontario's new-home warranty. The builder's seven-year warranty, administered by Tarion, protects against MSDs. For a home, coverage runs from the date of possession to the seventh anniversary of that date. For condominium common elements, it runs from the date the condominium corporation is registered.
Tarion describes three tests. The first is a defect in work or materials that causes a structural load-bearing element of the building to fail. The second is a defect that materially and adversely affects a load-bearing element's ability to carry the loads it was meant to carry. The third is a defect that materially and adversely affects the use of a significant portion of the building as a home. Tarion treats this use test as objective.
Tarion's examples include significant damage from soil movement and major cracks in basement walls. Collapse or serious distortion of joints or roof structure, and chemical failure of materials, also count. Some items are excluded even if they seem serious. These include damage to drains or services, damage to finishes, and dampness that does not come from failure of a load-bearing part. Floods not caused by the builder, heating and cooling appliances, and elevating devices apart from the surrounding structure are also excluded.
An MSD found in the first two years is covered and is claimed through the regular forms for those years. After the second year, you use Tarion's Major Structural Defect Form. It must be submitted no later than seven years from the date of possession, and you may submit more than one.
MSDs are rare, but they can be costly to fix. If you see signs of structural movement, report it in writing promptly and consider an opinion from a qualified professional.
Sources
- Tarion: Warranty coverage after you close
- Tarion: Seven-year warranty framework, major structural defects (RB03)
- Tarion: Claim forms and timelines
- Tarion: Common elements warranty coverage
Last reviewed October 16, 2026.
Related terms in New Build & Warranty
- Pre-Delivery Inspection The builder-led walkthrough before possession of a new Ontario home that records its condition on Tarion's PDI Form.
- Tarion The not-for-profit that administers Ontario's new-home warranty, covering defects for up to seven years and protecting deposits.
- Certificate of Completion and Possession The Tarion warranty certificate your builder provides at possession, recording the date that starts your warranty clock.
- Home Construction Regulatory Authority Ontario's regulator that licenses new-home builders and vendors and runs the public Ontario Builder Directory.
General information only, not legal, tax, or financial advice. Rules change and vary by province; confirm the current details with the relevant authority before you rely on them.