Where Does Your Condo Unit End? Understanding Unit Boundaries and Renovation Rules in Ontario

You've bought a resale condo and you want to renovate. Maybe you're removing a wall, replacing the flooring, installing pot lights, or updating the bathroom. Before you call a contractor, there is a legal question you need to answer: where does your unit end and the common elements begin?

In a freehold house, this is obvious. In a condominium, the answer is set out in the declaration — the founding document registered on title when the condo was created. And the answer has significant implications for what you can do, what approvals you need, and who is responsible when something goes wrong.

The Declaration Defines Your Unit

Ontario's Condominium Act requires that every condominium declaration define the boundaries of each unit. These definitions are technical and often counterintuitive. Common boundary formulations include:

• Upper surface of the floor slab to the lower surface of the ceiling slab — meaning the concrete structural elements are common elements, but everything attached to them (drywall, flooring, ceiling finishes) may be part of your unit.
• Including or excluding the drywall on interior and demising walls, depending on the declaration.
• Balconies — often defined as either part of the unit (exclusive-use common element area) or as common elements the owner has exclusive use of. The distinction affects maintenance responsibility and what you can install.
• Windows and exterior doors — these are frequently common elements even though they appear to be part of your unit.

The declaration is included in the status certificate package. Ask your lawyer to explain the unit boundaries before you purchase, especially if you anticipate renovating.

Common Elements You Do Not Own

Even if something is inside or attached to your unit, it may be a common element for which the corporation — not you — is responsible for maintenance and repair. Common examples:

• Structural walls — load-bearing or demising walls between units are often common elements. Removing or altering them typically requires board approval and may require engineering sign-off.
• Pipes, electrical conduit, and ductwork running through walls and ceilings — even where they supply your unit, portions may be common elements the corporation maintains.
• Windows and sliding doors — in many buildings these are common elements. If your window leaks or fails, the responsibility for repair may be the corporation's, not yours — but this cuts both ways: you may not be permitted to replace them yourself.
• Balcony structure — the balcony slab and railing may be common elements even if you have exclusive use of the balcony space.

What Renovations Typically Require Board Approval

Even for work that is entirely within your unit boundaries, certain types of renovation require written approval from the condo corporation before you begin. This is typically governed by the by-laws and sometimes a specific renovation policy.

Renovations commonly requiring approval:

• Removing walls — especially if there is any possibility of load-bearing or demising wall involvement.
• Installing hardwood, tile, or other hard flooring — most buildings require minimum sound insulation ratings (IIC and STC ratings) for hard surface floors to prevent noise transmission to units below.
• Plumbing changes — rerouting supply or drain lines, adding a bathroom, changing a sink location.
• Electrical work — adding circuits, upgrading the panel, installing dedicated lines for appliances.
• HVAC modifications — adding or relocating vents, installing a mini-split system on an exterior wall or balcony.
• Structural modifications — any work touching walls, ceilings, or floors that affect the building structure.

The approval process typically requires submitting renovation plans, sometimes accompanied by engineer drawings, and receiving written approval before work commences. Working without approval can result in orders to restore the unit at your own expense — and your renovation may not have been covered under the standard unit definition for insurance purposes.

The Standard Unit By-law and Renovations

The standard unit by-law (if the corporation has passed one) defines the baseline finishes for insurance purposes, but it also tells you something about what the corporation considers "standard" within the unit versus what qualifies as an improvement. Understanding the standard unit definition before you renovate helps you:

1. Know what your personal condo insurance needs to cover (improvements above the standard unit are your responsibility to insure).
2. Know whether the corporation's master policy would cover damage to your renovation in a loss scenario.

Common Pitfalls for Resale Buyers Who Want to Renovate

Buying Based on Planned Renovation That Requires Approval You Don't Have

If your purchase is contingent on being able to open up a kitchen, remove a wall, or install hardwood over concrete, confirm with your lawyer that those plans are feasible under the building's rules and approval process before you waive conditions.

Assuming the Previous Owner's Unauthorized Work Is Your Problem

Unauthorized renovations by previous owners can leave you responsible for bringing the unit into compliance. Your lawyer should ask about any known unauthorized renovations as part of the purchase review.

Removing or Damaging a Common Element by Mistake

Cutting into a wall that turns out to contain a common-element pipe can create significant liability. Always have the governing documents in hand and consider consulting the property manager before opening any walls.

Frequently asked questions