Legal Basement Apartments in Ontario (2026): Requirements, Permits and Costs by City

Short answer: a basement apartment in Ontario is legal when four things line up: zoning that permits the unit (every serviced urban lot in Ontario can have at least three units since November 2022), a building permit, construction that meets the 2024 Ontario Building Code, and an Electrical Safety Authority (ESA) inspection of the electrical work. Some cities, including Brampton, Mississauga, Markham and Pickering, also require you to register the unit. In the GTA a legal basement apartment typically costs $80,000 to $175,000 to build.

The rules changed significantly on January 1, 2025, when the 2024 Building Code took effect, and much of what is online, including the Province’s own consumer page from 2023, predates it. This guide covers the current requirements, what changes if you add a third unit, how to legalize an older suite, and the rules city by city. Everything was checked against the Building Code, provincial law and each city’s website in October 2026.

What makes a basement apartment legal

1. Zoning. Since November 28, 2022, Ontario’s Planning Act stops municipalities from banning up to three units on a serviced urban lot: three in the house, or two in the house and one in a backyard building. Cities cannot require more than one parking space for each extra unit and cannot set a minimum unit size. Several GTA cities now allow four.
2. A building permit. Required in every municipality, with drawings that show the suite meets the Building Code.
3. The Building Code. Ceiling height, bedroom windows, fire and smoke separation, alarms, sound, heating and exits all have rules, set out below.
4. Electrical. Electrical work needs its own ESA notification, separate from the building permit. Anyone you hire for it must be a Licensed Electrical Contractor.
5. Local registration or licensing, where it applies. See the city table below.

A second or third unit created inside an existing house is also exempt from municipal development charges under the Development Charges Act.

What the 2024 Building Code changed

The 2024 Code introduced the term secondary suite: a self-contained unit in a house that contains only one other dwelling unit. That definition matters, because several relaxations apply only when the house has exactly two units:

• Lower ceilings are allowed. At least 1.95 m, and 1.85 m under beams and ducts.
• A smoke-tight barrier can replace a rated fire separation. Instead of a 45-minute fire separation between the units, you can use a continuous smoke-tight barrier of 15.9 mm (5/8 inch) Type X drywall on both sides of the walls and the underside of the floor framing between units.
• Wireless alarm interconnection is allowed, which helps when each unit has its own electrical service.
• A shared exit does not need a second separate exit in most two-unit houses.
• No size cap from the Code. Ontario did not adopt the national code’s 80 m² limit on suite size, although some cities cap it in their zoning (Toronto does, below).

The requirements, one by one

Requirement	What the 2024 Code requires in a two-unit house
Ceiling height	1.95 m, or 1.85 m under beams and ducts. The full-height area must connect to the room entrances.
Bedroom windows	Each floor with a bedroom needs an openable window with at least 0.35 m² of clear opening and no dimension under 380 mm, unless a door on that floor opens directly outside. A window well needs at least 550 mm of clear space in front of the window.
Separation between units	A 45-minute fire separation, or the 15.9 mm Type X drywall smoke-tight barrier option. Beams and posts supporting the floor between units need Type X protection.
Smoke alarms	In every unit, on every storey including the basement, in every bedroom and in shared areas. Hard-wired with battery backup, with a visual (strobe) component, and interconnected so all alarms in the house sound together.
Carbon monoxide alarms	Required where there is a fuel-burning appliance, forced-air fuel heating or an attached garage, next to bedrooms and interconnected across the house.
Sound	A sound rating of STC 50 (or ASTC 47) between units.
Heating	Return air from one unit cannot be recirculated into the other, which in a newer house means separate systems.
Entrance	The Code does not require a separate entrance, but each unit needs a compliant way out, and many cities regulate where a separate entrance can go.

If your house is more than five years old

Most GTA basement conversions happen in existing houses, and the Code’s Part 11 offers “compliance alternatives” for buildings that have existed for at least five years. Among them: a 30-minute fire separation (or 15 minutes with interconnected smoke alarms in every unit), a set of construction details in place of the STC 50 sound rating, and keeping a single shared furnace in houses of up to four units if each unit has smoke alarms and a duct smoke detector shuts the furnace down. These alternatives are why it pays to have the design done by someone who knows Part 11: they can remove thousands of dollars of work without reducing safety.

Adding a third unit changes the rules

Because a secondary suite is defined as a unit in a house with only one other unit, a third unit takes away the two-unit relaxations: the smoke-tight barrier option, the 1.95 m and 1.85 m ceiling heights, the shared-exit exemption and the related sound and separation alternatives. The City of Oshawa’s guide notes that a three-unit building is considered an apartment building under the Building Code, and the drawings must come from an architect, engineer or BCIN-qualified designer. If you are planning more than one extra unit, our guide to Toronto multiplex rules covers the jump from two units to three.

Legalizing an older basement apartment

Many GTA basement units were built years ago without permits. Two routes exist:

• Build it to current standards with a permit. The usual route: the unit is brought up to the Building Code under a building permit, using the Part 11 alternatives for an older house where they apply.
• Fire Code Part 9.8 for very old two-unit houses. Two-unit houses that existed on July 14, 1994 can be retrofitted to the Ontario Fire Code instead, inspected by the local fire service. It sets its own rules for separation (30 minutes, or 15 minutes with interconnected alarms), exits and smoke alarms. Vaughan, for example, sends pre-1994 suites to a fire inspection instead of a permit, and Oshawa registers them for $500.

The rules city by city

City	Units per lot	Registration or licensing	Worth knowing
Toronto	Up to 4 citywide (6 in some areas)	No registry	No parking required. A secondary suite can be no more than 45% of the house’s interior floor area, except a whole basement in a one-storey detached house.
Mississauga	House plus 2 extra units; fourplexes permitted	Free registration after the permit is closed	No additional parking. The City refunds the permit fee for second and third units under its affordable rental program.
Brampton	3	Mandatory two-unit registration ($200), and citywide rental licensing since January 1, 2026	A side or rear entrance needs a 1.2 m clear path on your own lot. Not registering can bring a $1,000 to $1,500 penalty.
Vaughan	3	None found	One parking space per extra unit outside transit station areas. The entrance goes on a side or rear wall, not the main-entrance wall. A $2,575 refundable deposit applies.
Markham	3	Fire registration ($246 plus a $429.50 inspection)	Requires proof of two-unit insurance and an electrical report.
Richmond Hill	4	None shown	A 1.0 m clear path with 2.1 m headroom to the entrance.
Oakville	3	None, but a zoning certificate of occupancy is required	One parking space per extra unit.
Ajax	4	None found	No parking for the first extra unit, one each after. A 1.2 m path is required.
Pickering	3	Mandatory registration ($500) after fire and building inspections	One parking space per unit outside City Centre.
Oshawa	3	Rental licence in the rental area near Durham College and Ontario Tech	One parking space per extra unit.
Hamilton	4	Rental licensing in Wards 1, 8 and part of 14	A flat $515 building permit fee for a unit inside the house.

Rules change often, so confirm with your city before you design. One trap worth knowing: some city web pages still list minimum unit sizes, but the Planning Act has prohibited municipal minimum sizes for these units since 2022.

What a legal basement apartment costs

In the GTA, a legal basement apartment typically costs $80,000 to $175,000. Ours start at $80 per square foot. Recent reporting lines up: a contractor quoted in the Globe and Mail in April 2026 put suites at around $90,000 to start for 600 to 900 square feet, with a new separate entrance at about $30,000, and a 2025 Globe Financial Facelift case budgeted $175,000 in total for a rental-ready basement. Where your project lands depends on:

• Ceiling height. If the basement is below 1.95 m, lowering the floor through underpinning or a bench footing is the single biggest cost.
• The entrance. A new below-grade entrance with stairs is a major line item.
• Windows. Enlarging or cutting bedroom windows that meet the size rules.
• Plumbing. Whether drains sit below the sewer line and need an ejector pump.
• Heating. Separate systems in a newer house, or the shared-furnace alternative in an older one.

We will publish a full basement renovation cost guide covering finishing versus a legal suite. In the meantime, our basement renovation page has our current ranges.

What the unit can earn

There is no reliable published data on basement apartment rents specifically. The closest benchmark is CMHC’s October 2025 rental survey of purpose-built apartments, which put the average one-bedroom at $1,761 a month and the average two-bedroom at $2,046 across the Toronto area, with Mississauga at $1,746 and $2,005, Brampton at $1,778 and $2,032, and Oakville at $1,915 and $2,337. Rents across Toronto have been falling for two years, so plan on today’s figures.

Paying for it

• CMHC’s secondary suite refinance. Since January 15, 2025, an owner-occupier adding a suite can refinance with mortgage insurance up to 90% of the home’s value after the work, as long as that value is under $2 million and the property has no more than four units. Rentals under 90 days are not allowed.
• The Multigenerational Home Renovation Tax Credit, if the unit is for a senior or a family member eligible for the disability tax credit. It is calculated on up to $50,000 of costs at the lowest federal tax rate: 14.5% for the 2025 tax year (up to $7,250) and 14% from 2026 (up to $7,000).
• The federal $80,000 Canada Secondary Suite Loan does not exist. It was cancelled in the November 2025 federal budget before it launched.

Our guide to financing a basement suite walks through a worked example of the refinance.

The process, step by step

1. Feasibility check. Ceiling height, window locations, entrance options, drainage and your city’s zoning.
2. Design and drawings by a BCIN-qualified designer, architect or engineer, using the Part 11 alternatives where the house qualifies.
3. Building permit. For a complete house application, the Building Code sets a 10 business day review.
4. Construction and inspections, including the ESA inspection.
5. Close the permit and register or license the unit if your city requires it.

Thinking about a legal basement apartment?

We design and build legal basement apartments across Toronto and the GTA, from the feasibility check and drawings through permits, construction, inspections and registration. Book a free consultation and we will tell you what your basement can become and what it will cost. See our basement renovation services and our guide to renovation permits.

Legal basement apartment FAQs

What is the minimum ceiling height for a legal basement apartment in Ontario?

In a house with one secondary suite, the 2024 Building Code requires at least 1.95 m, and 1.85 m under beams and ducts. Those lower heights do not apply once the house has three units.

Do I need a separate entrance for a basement apartment?

The Building Code does not require one, but each unit needs a compliant way out, and most people want a private entrance. Many cities, including Brampton and Vaughan, regulate where an entrance can go and the path to it.

Do I need a fire separation between the units?

Yes, or the newer alternative: in a two-unit house, a continuous smoke-tight barrier of 15.9 mm Type X drywall can replace the 45-minute fire separation. Houses at least five years old have further compliance alternatives.

Do I have to register my basement apartment?

It depends on the city. Brampton, Mississauga, Markham and Pickering require registration, Brampton also licenses rentals, and Oshawa and Hamilton license rentals in certain areas. Toronto has no registry.

Can I legalize a basement apartment that was built without a permit?

Usually, yes. Most are brought up to the Building Code under a new permit. Two-unit houses that existed on July 14, 1994 can instead be retrofitted to Part 9.8 of the Ontario Fire Code and inspected by the fire service.

How much does a legal basement apartment cost in the GTA?

Typically $80,000 to $175,000, and ours start at $80 per square foot. Lowering the floor, adding a separate entrance and enlarging windows are the items that push a project toward the top of the range.

Do I need parking for a basement apartment?

Ontario caps it at one space per extra unit, and many cities require less. Toronto and Mississauga require no additional parking.