Retaining Wall Disputes Between Neighbours in Ontario: Ownership and Liability

A retaining wall near a shared property line rarely causes problems — until it starts to lean, crack, or fail, and suddenly two neighbours are arguing about who built it, who owns it, and who has to pay to fix it. Retaining wall disputes tend to be genuinely confusing because ownership isn't always obvious from looking at the wall, and the answer often depends on facts that took shape years before either current owner bought the property.

This article explains how Ontario generally sorts out ownership and liability for a retaining wall, and what to do if one is failing or has caused damage.

Step 1: Figure Out Whose Land the Wall Sits On

The starting point in most disputes is simple, even if the answer isn't: a structure generally belongs to the owner of the land it sits on. If a retaining wall is entirely within one property's boundary, that owner is typically responsible for it — even if it happens to hold back soil that benefits the neighbouring property by preventing erosion or slope failure onto it.

Where it gets harder:

• The wall straddles the property line. A wall built directly on or across a boundary can be treated as a shared structure, with both owners having an interest in it — similar in concept to a shared fence, though the legal treatment of a retaining wall isn't identical to fence-specific rules.
• Ownership isn't clear from a visual inspection. A property survey may be needed to determine exactly where the boundary falls relative to the wall.
• The wall was built by a previous owner, or by the municipality, or as part of an original subdivision development. Older walls sometimes come with no clear paper trail at all.

A current property survey — and, where available, historical building permits — is usually the first practical step in figuring out where things actually stand.

Step 2: Understand Who's Responsible for Maintenance and Failure

Even once ownership is sorted out, liability for damage caused by a failing wall is a separate question. Generally:

• The owner of the wall (or the land it sits on) has an obligation to maintain it in reasonably safe condition.
• If a wall fails because of poor original construction, neglect, or a failure to address known deterioration, the responsible owner may be liable for resulting damage to a neighbour's property.
• If a wall fails because of something the neighbouring property owner did — for example, altering drainage, adding load near the wall, or excavating nearby — liability may shift, in whole or in part, toward that neighbour instead.

This is why retaining wall disputes often turn into genuine fact investigations: was the wall properly built and maintained, and did anything either owner did contribute to the failure?

Common Scenarios and How They're Generally Approached

What to Do If a Retaining Wall Is Failing or Has Failed

• [ ] Take photos and video of the current condition, and continue documenting any progression
• [ ] Get a property survey if ownership of the wall isn't already clear
• [ ] Consider a structural or geotechnical assessment if failure seems imminent or has already caused damage
• [ ] Raise the issue with your neighbour in writing, referencing what the assessment shows
• [ ] If there's immediate risk to safety or property, contact your municipality — some jurisdictions have bylaw authority over unsafe structures
• [ ] Keep records of any costs you incur addressing immediate safety risks, in case they're later recoverable

When It Becomes a Legal Dispute

If a neighbour won't address a failing wall that's their responsibility, or disputes liability for damage that's already occurred, the matter generally becomes a civil claim for damages (the cost of repair or the harm caused) and, in some cases, an order requiring repair. As with most property disputes, the appropriate court usually depends on the dollar value involved — many retaining wall disputes fit within Small Claims Court's jurisdiction, while larger or more complex cases, or those seeking a mandatory repair order rather than money, may need the Superior Court of Justice.

Court-ordered injunctive relief (an order requiring someone to act, not just pay) is generally harder to obtain than a damages award, so most of these disputes are framed primarily around cost recovery unless there's a genuine, ongoing safety risk.

Frequently asked questions