In-law suites in Canada: what makes one legal, what it costs, and the tax credit

Your mother is moving in, or your grown kid needs a place to land, and the basement is sitting there. Whether that basement becomes a legal in-law suite or a nice spare room comes down to one question: does it have its own kitchen?

What is an in-law suite?

"In-law suite" isn't a legal term. The codes call it a secondary suite, and Ontario's Planning Act calls it an additional residential unit. Ontario defines a second unit as "a self-contained dwelling unit with a private kitchen, bathroom facilities and sleeping areas" (Ontario). Add a private entrance and you have a separate dwelling unit, which needs a permit and must meet the code for suites. A finished basement with a bedroom and bathroom but no kitchen is still part of your house, and only needs a regular renovation permit.

Are in-law suites legal in Ontario?

Yes, on most urban lots. Since 2022, Ontario municipalities can't ban up to three units on a serviced residential lot: up to three in the house, or two in the house and one in a backyard building (Planning Act). They can't require more than one parking space per extra unit, and they can't set a minimum unit size. The unit can be rented to anyone, and you don't have to live on site. Rural lots on a well and septic aren't covered by that rule, so check your township's zoning; our Ontario zoning pages cover 327 municipalities. A second unit inside an existing house doesn't pay development charges (Ontario).

The 2024 Ontario Building Code sets the construction rules. Oshawa's 2026 summary lists the main ones (Oshawa):

• Fire separation: 15.9 mm Type X drywall on both sides of walls and under the floor between the units, or a 30-minute fire separation, unless the house is sprinklered.
• Alarms: smoke alarms on every storey and in every bedroom, all interconnected so one sounds them all, plus CO alarms near bedrooms when there's a fuel-burning furnace or water heater.
• Ceiling height: at least 1.95 m in a basement suite, and 1.85 m under beams and ducts.
• Bedroom windows: an opening of at least 0.35 m², no side under 380 mm, unless the level has a door straight outside.
• Heating and sound: in a house under 5 years old, a separate heating system and STC 43 sound separation. In an older house, the furnace can be shared if a duct smoke detector shuts it off.

Most Ontario municipalities want permit drawings from an architect, engineer or a BCIN-qualified designer, and you'll need a separate ESA electrical permit. A suite that existed on July 14, 1994 falls under the Fire Code's retrofit rules instead (Fire Code 9.8). Some cities add registration: Mississauga requires it, with a fire inspection, and refunds the building permit fee once the unit passes inspection (Mississauga).

Our take: measure your basement ceiling before you call anyone. If it's under 1.95 m, you're looking at underpinning or lowering the floor, and that single item can double the budget.

What are the in-law suite rules in BC and Alberta?

BC: the 2024 BC Building Code needs a 45-minute fire separation between units, reducible to 30 or 15 minutes with more interconnected photoelectric smoke alarms, plus 2.1 m headroom (Kamloops). The code sets no size limit; municipalities do (BC). Vancouver has its own building by-law.

Calgary: a suite needs egress-size bedroom windows, its own bathroom and cooking facilities, and a private entrance from outside (a shared stairwell is fine). Legal suites go on the city's public Secondary Suite Registry, and the amnesty that waives development permit and registration fees runs until December 31, 2026 (Calgary).

Edmonton: every suite needs a development permit ($415 in 2026) plus building and trade permits, and only one suite is allowed per house (Edmonton). The province has ordered Edmonton to change its zoning bylaw by January 2027, so check the current rules before you apply.

How much does an in-law suite cost?

Contractor and cost-guide figures for 2026, not independent surveys:

RenoCalc's line items show where the money goes: a separate entrance is $8,000 to $15,000, each egress window $4,000 to $7,500, the fire separation $4,000 to $8,000, a kitchen $8,000 to $16,000 and a bathroom $6,500 to $15,500. An unfinished basement with a low ceiling and no side door sits at the top of the range. For a separate building in the yard, see our ADU guide.

Is there a tax credit for an in-law suite?

Yes, the federal Multigenerational Home Renovation Tax Credit. It's refundable and covers up to $50,000 of costs to build a self-contained unit so a relative can live with you (CRA). The rate follows the lowest federal tax rate: 14.5% for 2025, or up to $7,250. The person moving in must be 65 or older, or 18 or older and eligible for the disability tax credit, and you claim it once per person. Permits count; appliances, financing costs and your own labour don't. A suite for a healthy adult child under 65 doesn't qualify.

The federal Canada Secondary Suite Loan Program was cancelled before it took applications, but CMHC-insured refinancing can fund a suite; our suite funding guide has the details.

Do I pay tax if a family member pays rent?

Not if the rent only covers your costs. The CRA says rent below fair market value from a family member isn't reported as income, and you can't claim rental expenses (CRA). At market rent, you report the income and deduct expenses. Selling is the bigger question: the CRA says a structural change to create rental space can be a partial change in use of your home, which can make part of the gain taxable (CRA folio S1-F3-C2). Ask an accountant before you build if you plan to charge rent.

Tell your insurer before construction starts. The Insurance Bureau of Canada says your policy covers family members living in the suite, but a non-family tenant needs their own tenant insurance, and the suite can raise your premium (IBC). Expect a higher property assessment once the suite is finished.