What a Legal Basement Apartment Actually Requires in Ontario
What a Legal Basement Apartment Actually Requires in Ontario
Ontario’s More Homes Built Faster Act, 2022 requires municipalities to permit at least three residential units as of right on most lots that already contain a home. A legal second suite must meet the 2024 Ontario Building Code, in force January 1, 2025: a minimum 1.95 metre ceiling height across the required area, fire separation between dwelling units, an egress window of at least 0.35 square metres in each bedroom, interconnected smoke alarms in both units, carbon monoxide alarms where required, and a building permit with ESA electrical approval.
Last updated: August 2026
1.95 metres
Minimum ceiling height, and the usual disqualifier
0.35 sq m
Minimum egress window opening in each bedroom
3 units
Permitted as of right on most lots under Bill 23
A legal second suite is the single best return on investment available to a GTA homeowner right
now, and the rules changed in your favour twice in the last few years.
An illegal one is a liability that follows you to the closing table. The difference between them
is a permit and a handful of measurements.
You are probably allowed, and that is new
Ontario’s More Homes Built Faster Act, better known as Bill 23, set a province-wide floor in 2022.
Municipalities must permit at least three residential units as of right on most lots
that already contain a home. That can be three units inside the main building, or two units plus an
ancillary unit such as a garden suite.
In much of Toronto a basement second suite is now permitted as of right in residential zones,
without a minor variance, without a parking space for the second unit, and without development
charges or parkland fees.
That is a genuine change. People who looked at this five years ago and were told no should look
again.
The numbers that decide whether your basement qualifies
1
Ceiling height: 1.95 metres
About 6 feet 4 and three quarter inches, across the required floor area including the path to the exit. This is the one that disqualifies older basements most often, and it is the hardest to fix because the answer is underpinning.
2
Fire separation between the units
The Building Code requires a fire resistance rating between dwelling units. Lighter separations are permitted in two unit houses where interconnected smoke alarms are installed throughout, which is usually the practical route in an existing home.
3
An egress window in every bedroom
Minimum openable area of 0.35 square metres with no dimension under 380 millimetres, and a sill no more than 1.5 metres above the floor. A window well often makes this achievable where the opening alone would not.
4
Interconnected smoke alarms, both units
Alarms in both dwelling units and common areas, interconnected so they sound together. This is not optional and it is what makes the lighter fire separation permissible.
5
Carbon monoxide alarms
Required adjacent to sleeping areas where the home has a fuel burning appliance or an attached garage.
6
A building permit, and ESA sign off
You always need a permit. Drawings, inspections at stages, and Electrical Safety Authority approval for the electrical work.
The 2024 Building Code took effect January 1, 2025, so quotes and advice from before that are on the wrong version
Ontario moved to the 2024 Building Code with effect from January 1, 2025. If you got a contractor quote, a design, or a blog article about basement apartments before that, it may be built on the previous code. This matters most on the details that decide feasibility, particularly heights, separations and alarm requirements. Ask your designer which code edition their drawings are to. It is a fair question and the answer should be immediate.
Why the legal version is worth the money
I get asked this constantly, usually by someone who already has a tenant down there.
It is worth more at sale, and it appraises. A registered, permitted second
suite is income a lender and an appraiser can actually count. An unpermitted one is a room with a
stove in it, and a cautious buyer’s lawyer will treat it as a risk to be discounted.
Insurance. An undisclosed second unit is a coverage problem exactly when you
need coverage.
It transfers cleanly. An illegal suite is something you have to disclose or
actively conceal, and neither of those is a good position at the negotiating table.
Fire safety, which is the actual point. The egress window and the
interconnected alarms exist because people have died in basement apartments without them.
Before you spend anything
Measure the ceiling height first. Floor to underside of joists, in several places, including the
route to the exit. If you are meaningfully under 1.95 metres, the conversation changes to
underpinning, which is a different project with a different budget, and it is better to know that
on day one than after you have paid for drawings.
This is general information, not a code review
Building Code requirements are technical, they are applied by your municipality, and zoning
still varies locally even under the provincial floor. Talk to your municipal building department
and use a designer who does second suites regularly. Nothing here replaces a permit application.
Sources: Ontario’s More Homes Built Faster Act, 2022 (Bill 23), for the as of right permission for additional residential units, and the 2024 Ontario Building Code, in force January 1, 2025, including the requirements for ceiling height, fire separation between dwelling units, egress window sizing, interconnected smoke alarms and carbon monoxide alarms.
Where This Comes From
Written from the More Homes Built Faster Act, 2022 and the 2024 Ontario Building Code, in force January 1, 2025. Zoning still varies locally, so confirm with your municipal building department before relying on any of it.
In most cases yes. The More Homes Built Faster Act, 2022 requires municipalities to permit at least three residential units as of right on most lots that already contain a home, and in much of Toronto a basement second suite is permitted as of right without a minor variance, without parking for the second unit and without development charges.
What is the minimum ceiling height for a basement apartment in Ontario?
1.95 metres, roughly 6 feet 4 and three quarter inches, across the required floor area including the path to the exit. This is the requirement that most often disqualifies older basements, and the remedy is underpinning, which is a substantially larger project.
What size window does a basement bedroom need?
An egress window with a minimum openable area of 0.35 square metres, no dimension less than 380 millimetres, and a sill no more than 1.5 metres above the floor. A window well is often what makes this achievable in an existing basement.
Do I need a permit for a basement apartment?
Yes, always. The process involves drawings, inspections at stages, and Electrical Safety Authority approval for electrical work. An unpermitted suite creates insurance, financing and disclosure problems that surface at the worst time, which is when you sell.
Is a legal basement apartment worth the cost?
In my experience yes, for a specific reason: a permitted suite produces income an appraiser and a lender can actually count, whereas an unpermitted one is treated as a risk to be discounted. The safety requirements exist because people have died in basement apartments without egress and interconnected alarms.
If you are weighing a second suite, measure the ceiling height before you spend anything else, then talk to me about what it would actually add to the value here rather than in general. Those two numbers decide the whole project.
