Legal basement apartment requirements in Toronto

A basement apartment built in Toronto today is legal when three things line up: the zoning by-law allows a secondary suite in your house, the suite meets the Ontario Building Code, and a building permit for it has been issued, inspected and closed. The Fire Code applies on top of that from the day someone lives there.

Minimum ceiling in a suite, about 6'5"

1.95 m

Clear height under beams and ducts, about 6'1"

1.85 m

Of the home's interior floor area, the most a suite may take

45%

Type X drywall, one option between units in a newer house

15.9 mm

A house that was already used as two units on November 16, 1995 is a special case: the Planning Act keeps its second-unit rules of that time in force for that house (s. 76).

Zoning: can your house have a secondary suite?

Toronto's zoning permits a secondary suite in a detached house, a semi-detached house or a townhouse, one per dwelling unit (By-law 569-2013, s. 150.10.20.1). The by-law's name for a basement apartment is a secondary suite: a self-contained home with its own kitchen and bathroom, inside and subordinate to a dwelling unit. In some apartment, commercial and institutional zones, the house must already exist lawfully.

• Size: no more than 45% of the interior floor area of the dwelling unit it sits in. In a one-storey detached house, a basement suite may take the whole basement (s. 150.10.40.40).
• Parking: none required for a secondary suite (Table 200.5.10.1). A new space you add for the suite needs a marked, energized outlet capable of Level 2 EV charging (s. 200.5.1.10(14) and 200.5.200.5).
• Entrance: since By-law 474-2023, zoning no longer limits front entrances for secondary suites. A new stair down to a side or rear door still goes through the zoning review, with its setbacks to the lot lines on the site plan.

Minimum ceiling height: the first number to check

The Building Code sets the ceiling in a secondary suite at no less than 1.95 m (about 6'5"), and the clear height under beams and ducts at no less than 1.85 m, about 6'1" (Div. B, 9.5.3.1). The part of each room that meets those heights has to connect to the room's entrance. An older house gets no allowance here: the Code's renovation relief for lower rooms leaves secondary suites out (Table 11.5.1.1.-C, C105).

How to measure

Measure from the floor to the underside of the joists, then under every beam and duct, and subtract the new floor finish and drywall ceiling. Ducts are often the lowest point, and many can be rerouted. Joists that are low everywhere, or a beam below 1.85 m that can't move, mean the floor comes down.

When the ceiling is too low: underpinning or benching

There are two ways to bring the floor down:

Toronto Building sets these engineering rules for underpinning:

• A Professional Engineer designs and reviews on site any underpinning that goes below a neighbouring building's footing within the soil's angle of repose, the steepest slope at which the soil stays stable.
• Engineer design and site review also apply where more than 1.2 m (about 4 ft) of wall is left without lateral support, or where the soil is clay or silt.
• On every underpinning job, an engineer must test and report on at least the first and last stages, or the inspections won't pass.

It is also the moment to add a walkout, since the new stair lands at the new floor level. Our basement underpinning page covers the drawings and the engineer's part.

What the Ontario Building Code requires for the suite

Turning one home into two counts as a change of major occupancy, so the suite must meet the Code's rules for room sizes, heights, windows, plumbing fixtures, ventilation and electrical (Div. B, 11.4.2.3 and 11.4.3.4). In a house at least five years old, Part 11 applies, and its compliance alternatives can replace many Part 9 rules without special approval (Div. A, 1.3.3.3B; Div. B, 11.5.1.1). A newer house follows Part 9 as written.

Fire separation in a newer house

In a newer house the rating between units is 45 minutes, or 1 hour where a unit has two or more storeys, basement included. The 15.9 mm Type X option is 5/8" fire-resistant drywall, installed as a continuous smoke-tight layer; beams, posts and walls holding up the floor between the units get it too (9.10.8.3, 9.10.9.16).

Room sizes

Room sizes have no older-house alternative. Built-in cabinets lower each bedroom minimum by 1 m², and a suite that sleeps one or two people needs less (9.5.3A to 9.5.3E):

• An 11 m² living area where it shares a room with the kitchen and dining space
• A 3.7 m² kitchen
• For a bachelor, 13.5 m² in all

The way out

Under Part 9, the suite's way out may not pass through the other unit or a service room such as the furnace room, though the two units may share an exit stair or hall that is separated from both (Div. B, 9.9.7.5, 9.9.9.3 and 9.10.9.16). In a house at least five years old, any one of these is accepted instead (Table 11.5.1.1.-C, C136 and C139):

• Its own door straight outside, sliding doors included, with reasonable access to ground level and smoke alarms in both units.
• A shared exit, such as a stair to a side door, enclosed by a 30-minute fire separation and reached without passing through either unit or the furnace room, with interconnected smoke alarms in both units and the common areas.
• A route through the other unit, if the suite also has an escape window that opens without tools: 0.38 m² clear with no side under 460 mm, a sill within 900 mm of the floor and 1 m of the ground outside, 1 m clear in a window well, and interconnected alarms.
• A route through the other unit in a sprinklered house, with smoke alarms in both units.

Bedrooms add one more rule: each floor level with a bedroom needs an escape window sized as in the table, with 550 mm clear in front if it sits in a window well, unless a door on that level leads straight outside (9.9.10.1). A new door to the outside often settles both rules; a below-grade one is drawn to the City's basement entrance guide.

Alarms and heating

Smoke alarms go on every storey, in and outside every bedroom and in any shared hall, stair or other common space; one sounding sets off all of them in both units, and wireless links are accepted (9.10.19).

CO alarms go beside each bedroom, and on each storey without one, where the suite meets any one of these:

• It has a fuel-burning appliance or flue.
• It shares a wall, floor or ceiling with one, or with a garage.
• It is heated by a fuel-fired furnace.

A bedroom that adjoins a garage or a fuel-burning appliance outside the suite, such as the furnace, gets one inside, and so does a furnace room outside both units (9.32.3.9A, 9.32.3.9B).

Fire Code rules for an existing two-unit house

The Ontario Fire Code governs buildings in use. Its Section 9.8 sets the minimum fire safety for a detached, semi-detached or row house with two units, up to 3 storeys and 600 m² in building area, where one unit sits above the other or two units side by side share an inside escape route. It does not apply where the house satisfies the Building Code's fire safety requirements, as a suite built and inspected under a building permit should (Fire Code, Div. B, 9.1.2.2 and 9.8.1.1).

• Separation and alarms: a 30-minute fire separation around each unit, or 15 minutes with interconnected smoke alarms wired with no disconnect switch, and at least one smoke alarm on every storey of each unit; ducts need no fire dampers (9.8.2.2, 9.8.2.5, 9.8.4).
• A way out: the unit's own door straight outside with direct access to ground level; or a shared route in a 30-minute enclosure that leads straight outside without entering the other unit; or a route through the other unit plus an escape window sized as in the older-house list above, with interconnected alarms (9.8.3).
• Existing work: lath and plaster or gypsum board walls and ceilings count as 30 minutes, plasterboard with a plaster skim coat as 15, and 45 mm solid-core wood, hollow metal or kalamein doors with self-closers in hollow metal or solid wood frames are accepted, but only if they were in place on July 14, 1994; newer work has to show its rating under the 1994 Building Code's rules. A house sprinklered to NFPA 13D keeps its separations and escape routes from that date as they are (9.8.1.2, 9.8.2, 9.8.3.5).
• Electrical: the fire department may order an Electrical Safety Authority inspection at the owner's cost, with hazards repaired by a licensed electrical contractor (9.8.6).

CO alarms come from the Fire Code's Section 2.16, unless they were installed to the Building Code as it read on or after January 1, 2025. Since January 1, 2026, a suite heated by a fuel-burning furnace outside it needs them too, and every suite that needs them has one next to each sleeping area and on every storey. In a rental, the landlord is responsible.

Legalizing an existing basement apartment vs. building a new one

The permit is the same either way, and the Building Code Act forbids the work without one (s. 8(1)). For an existing unit, the drawings show the basement as it is and what changes, and the rules above apply in full, compliance alternatives included. The difference is what the inspector can see; inspections happen at set stages:

1. 01Structural framing, with the plumbing and HVAC rough-ins
2. 02Fire separations, before any finishes
3. 03Insulation and vapour barrier
4. 04The finals

Toronto Building requires any element covered before its inspection to be uncovered, so in a finished unit expect to open ceilings and walls where the separation, ducts and pipes run.

If the unit is rented, the application's Rental Renovation Licence Screening Form shows whether the City's rental renovation licence (Municipal Code Chapter 662) also applies.

The building permit and inspections

1. 01
   Drawings and forms

   Once the suite is designed: a site plan on your survey with a zoning summary, floor plans with every alarm and plumbing fixture, sections with ceiling heights and stairs, and construction details. The City's forms and a Plumbing Data Sheet go in with them, all as PDFs, and HVAC work adds what the City's Residential Mechanical (HVAC) Guide asks for.

2. 02
   City fees

   Toronto Building's 2026 rates are $11.53 per m² of altered floor area plus $56.33 for the new unit, with a $214.79 minimum: a 60 m² suite is $748.13. Underpinning adds $12.37 per linear metre. Plumbing and HVAC permits filed with the building permit add no fee for work inside the house. No permit issues until the fees are paid.

3. 03
   City review

   A one-to-two-unit conversion qualifies for Toronto Building's Express Services, whose goal is a review within 3 business days of intake, as long as no permit for a new house or an addition is active.

4. 04
   Inspections

   Book each mandatory inspection as the work reaches it, with a full-size colour print of the permit drawings on site. The permit fee covers them.

5. 05
   Close the permit

   Book the final inspection to close the permit; Toronto Building warns that an open permit can complicate a future sale. Electrical work is reported to the Electrical Safety Authority separately from the building permit, and ESA issues a Certificate of Acceptance once it passes.

How to start a basement apartment

Start with the basement as it stands:

• Measure the clear heights, as above.
• Photograph the stair, the furnace room and every window.
• Photograph the outside wall where a door could go.
• Find your survey.

Those few facts decide the design: whether the floor comes down, which rooms sit against windows that can be enlarged, where the kitchen and bathroom meet the drain, how the suite gets outside and whether the furnace stays shared. Design the suite first, then draw the permit set from that design, so the examiner reviews a home that already works.