Legal basement apartment (secondary suite)합법 지하 유닛, 세컨더리 스위트

What is it?

A secondary suite is a second home inside one house. Ontario’s guide calls it "a self-contained dwelling unit with a private kitchen, bathroom facilities and sleeping areas." The City of Toronto defines it as a unit inside, and smaller than, the main unit of a detached house, semi-detached house or townhouse, and says the most common example is a basement apartment.

"Legal" means four things are all in place: 1) the zoning for the lot allows it, 2) the city issued a building permit and the work passed inspection, 3) the unit meets the Ontario Building Code minimums (ceiling height, windows, fire separation, alarms, exits), and 4) the electrical work had an Electrical Safety Authority (ESA) permit and inspection. An existing unit may also have to meet the Fire Code, so check with the city fire department.

Listing phrases such as "finished basement with kitchen", "in-law suite" or "retrofit status not warranted" do not mean the unit is legal. You need to check the permit records yourself.

Ontario and Toronto rules

• Ontario’s Planning Act stops a municipality from passing a by-law that prohibits two residential units in a detached house, semi-detached house or rowhouse (three with one in a separate building) (s. 35.1 (1)). A by-law cannot require more than one parking space for the extra unit (s. 35.1 (1.1)) or set a minimum floor area for it (s. 35.1 (1.2)).
• Ontario Regulation 462/24 sets standards (separation distances, lot coverage and so on) for lots with up to three units. The City of Toronto says secondary suites are covered by this regulation, and that four or more units fall under city by-laws instead.
• Toronto: secondary suites are permitted in all Residential zones. Since May 2023 multiplexes of up to four units are allowed city-wide, and since June 2025 up to six in some areas (Toronto and East York District and Ward 23).
• Other GTA cities (Markham, Vaughan, Richmond Hill, Mississauga and so on) each have their own by-laws and registration systems. Check with the building department of the city where the house is.

What a legal unit needs: Building Code minimums (house over five years old)

These are the minimums described in Ontario’s guide "Add a second unit in your house". A house less than five years old is treated as new construction, with stricter rules.

• Ceiling height: a basement unit needs at least 1.95 m (6 ft 4¾ in) over the whole required floor area, including the route to the exit.
• Room sizes: for example, a bachelor layout that combines sleeping, living, dining and kitchen space must be at least 13.5 m² (145 sq ft). Each room type has its own minimum.
• Windows: at least 5% of the floor area in living and dining rooms and 2.5% in bedrooms. Kitchens, bathrooms and laundry rooms do not need windows.
• Fire separation: a 30-minute fire separation between the units and between units and common areas. It can drop to 15 minutes if the whole house has interconnected smoke alarms.
• Smoke alarms: on every level, outside sleeping areas, in each bedroom of the second unit, and in shared areas such as entrances and laundry rooms. They must meet CAN/ULC S531 and flash a light when activated.
• Carbon monoxide alarms: required if the house has a gas or propane furnace or an attached garage, near bedrooms and in the furnace room.
• Exits: a separate exit is best. A shared exit needs a 30-minute fire separation and interconnected alarms, and if one unit’s exit passes through the other unit there must be an escape window. A basement escape window needs an unobstructed opening of at least 0.38 m² (4.1 sq ft), at least 460 mm (18 in) in the openable dimension, and no more than 900 mm (2 ft 11 in) above the floor.
• Plumbing: separate water shut-off valves for each unit, access to laundry, and possibly a backwater valve in areas prone to flooding.
• Heating: one furnace and shared ducts are allowed, but a special duct smoke detector (UL 268A) that shuts the furnace down is required. Kitchens and bathrooms need an exhaust fan or a window that opens.
• Electrical: a light and switch in every room and switches at the top and bottom of stairs. Electrical work needs a separate ESA permit and inspection.

These numbers were checked on the ontario.ca guide on October 30, 2026. The guide notes that parts of it have not yet been updated for the 2022 planning changes, so confirm current standards with the city building department.

Getting a permit in Toronto, step by step

1. Check the zoning: look up the lot on the Zoning By-law 569-2013 interactive map, or call Toronto Building Customer Service (416-397-5330). If the plan does not meet the by-law, you need a minor variance from the Committee of Adjustment first.
2. Design: a qualified designer (with a registration number), architect or engineer prepares floor plans, sections, a site plan and construction details in PDF. The drawings must show smoke and carbon monoxide alarm locations and plumbing fixtures.
3. Forms: the "Application to Construct or Demolish", Schedule 1 (Designer Information), the Assumption of Responsibility form if an engineer sealed the drawings, and the "Rental Renovation Licence Screening Form" if the work affects a rented unit (Toronto Municipal Code Chapter 662).
4. Apply: submit online through Toronto Building Online Services, or by email to bldapplications@toronto.ca. Ontario’s guide says you hear back within 10 business days on a complete application.
5. Fees (effective January 1, 2026): $11.53 per m² for interior alterations plus $56.33 for each new residential unit. Mechanical (HVAC) and plumbing permits are separate.
6. Build and inspect: city inspectors check framing, insulation, plumbing, finishes and other stages. Electrical work gets its own ESA permit and inspection. The job is done only after the final inspection passes.

Risks of buying a home with an illegal unit

• City orders: building without a permit or against the Building Code breaks the Building Code Act (ss. 8 and 36). The city can issue orders, and an individual faces a fine of up to $50,000 for a first offence. You may have to bring the unit up to code or remove it.
• Retrofit cost: a ceiling under 1.95 m can mean underpinning (digging out the floor), a major job. Redoing fire separations, escape windows and wiring is costly too. Get quotes from contractors.
• Insurance: an insurer may refuse to cover a tenant or incidents in an illegal unit, or raise the premium. Ask the insurer directly.
• Financing: a lender may not count rent from an illegal unit as income. Lenders differ, so ask a mortgage professional.
• Tenants: a tenant does not lose their rights because the unit is illegal. If you buy a tenanted home and must remove the unit, Residential Tenancies Act procedures apply, so ask a lawyer.
• Resale: the next buyer and the appraiser will ask the same questions. To advertise a "legal unit" you need the permit records.

How to check

• Ask the seller for the building permit number, the final inspection record and the ESA electrical inspection certificate. The word "legal" is not evidence.
• Ask the city building department for the address’s permit history and any open orders. In Toronto, contact Toronto Building Customer Service. This is separate from your lawyer’s title search.
• Put a condition in the offer, for example "conditional on the buyer confirming the legality of the unit through city records". Check within the condition period and keep the right to walk away.
• At the home inspection, measure the ceiling height, escape window size, fire separation, alarms and separate exit yourself, using the Building Code list above.
• If the unit is illegal, negotiate the price, budget for the retrofit, or walk away.

If you plan to rent it out

Rent from a legal unit can help carry the mortgage. Ontario’s guide states that development charges are not collected for a second unit built in an existing house.

The moment you rent it out, you take on landlord duties under the Residential Tenancies Act (standard lease, repairs, rent increase rules). A shared furnace can cause temperature, odour and noise issues, so the guide suggests separate heating where possible.

A basement unit created after November 15, 2018 may be exempt from the rent increase guideline if conditions are met, such as the owner living in another unit of the same house when it was first rented (Residential Tenancies Act, s. 6.1 (3)). See "Rent control exemption".

Example