Converting a basement into a new suite
Whether the basement is unfinished or already finished, the first checks are the same. Each one can stop the project or change its scope, so settle them before paying for full drawings:
- Building type and zoning. A secondary suite is permitted in a detached house, semi-detached house or townhouse, one per dwelling unit (Zoning By-law 569-2013, 150.10.20.1 (opens in a new tab)). The City’s interactive zoning map (opens in a new tab) shows the zone for your address.
- Suite size. The suite’s interior floor area can be no more than 45% of the interior floor area of the house it is in. In a one-storey detached house, a basement suite may take the whole basement (150.10.40.40 (opens in a new tab)). A second unit that is not subordinate in size is planned as a two-unit conversion under the City’s multiplex conversion guide (opens in a new tab) instead.
- Ceiling height. Measure to the ceiling and to the underside of every beam, duct and pipe run. The minimums are in the table below.
- Exits and windows. Note every door to the outside and the size and sill height of each basement window.
- Age of the house. If the house has existed for at least five years, Part 11 of the Building Code applies and allows listed compliance alternatives for existing houses (2024 Building Code, Div. A 1.3.3.3B (opens in a new tab)). A newer house generally has to meet the new-construction rules.
The approval sequence is then: design and drawings, a building permit application with any plumbing and HVAC permits, an electrical permit from the Electrical Safety Authority, construction with City inspections, and a final inspection to close the permit. Each step is set out under permits, inspections and closing the permit.
Your basement already has a kitchen and bathroom
Fixtures show how a space is used, not whether it was approved. A real estate listing that says “legal”, a history of tenants or a single inspection visit is not an approval record either. The records that do show approval are held by the City:
- Building permit records. Toronto Building discloses drawing records of earlier permit applications. Apply with the City’s form to bldrecords@toronto.ca; the 2026 fee is $76.98 per disclosure and the City aims to process requests within 30 business days (City (opens in a new tab)). Look for a permit that describes creating a second unit, and for its final inspection.
- Property Information Report. It lists issued building permits on file, the status of inspections and outstanding orders under the Building Code, zoning and property standards by-laws. It costs $214.79 in 2026 and takes about five business days. The City notes that it does not outline permitted use (City (opens in a new tab)), so it is a check for open permits and orders, not a statement that a suite is legal.
- Online permit status. The City’s status search only covers active permits up to 10 years old and permits closed or cancelled within the past month (City (opens in a new tab)). An older suite will not appear there even if it was approved.
Missing records do not by themselves make an older suite illegal, and a suite predating current rules may fall under a different regime. Toronto Fire Services states that Section 9.8 of the Ontario Fire Code applies to two-unit houses that existed on or before July 14, 1994 where one unit is above the other, or the two share an interior means of escape (Toronto Fire Services (opens in a new tab)). That section sets retrofit standards: for example, each unit separated by a 30-minute fire separation, or 15 minutes with interconnected smoke alarms, and a means of escape meeting one of several listed arrangements (Fire Code 9.8.2 and 9.8.3 (opens in a new tab)). Toronto Fire Services inspects on request, for a fee, through its request-for-service form (City (opens in a new tab)).
If there is no permit and the suite is not covered by that retrofit section, the usual route is to treat it as a new suite: a permit application with drawings of the existing space, followed by inspections. Work already built may have to be opened up, since elements covered before inspection must be uncovered for it (City (opens in a new tab)). The City also charges a “work without permit” fee of 50% of the permit fees when work that needed a permit started without one (City (opens in a new tab)).
Which requirements can change the project?
The rules below are from the 2024 Ontario Building Code, in force since January 1, 2025 (Building Code Compendium (opens in a new tab)). Where a house at least five years old can use a different Part 11 compliance alternative, the table says so.
Where to measure in your basement
- Floor to finished ceiling, in each room.
- Floor to the underside of beams and ducts, at the lowest points, including pipes and bulkheads.
- Clearance above the stairs, from the line of the stair nosings up to the lowest point overhead.
- Window opening and window well: the height and width of the part that opens, the sill height, and the depth of the well in front of the window.
- Exit location: each door the basement could use to reach the outside, and whether the route passes through another part of the house.
| Item to check | Why it matters | Establish before requesting a quote |
|---|---|---|
| Zoning and building configuration | One secondary suite per dwelling unit in a detached house, semi or townhouse, at most 45% of the interior floor area (whole basement allowed in a one-storey detached house) (150.10 (opens in a new tab)). | The zone, the building type, and the suite and house floor areas. |
| Ceiling height and obstructions | Ceilings in a secondary suite at least 1.95 m; clear height under beams and ducting at least 1.85 m; the compliant area must connect to each room’s entry (9.5.3.1.(2) to (4)). Stairs need 1.95 m clear, 1.85 m under beams and ducts (9.8.2.2). The Part 11 low-ceiling alternative excludes secondary suites (C105), so this also applies in older houses. | Measured heights to the ceiling and to the lowest beam, duct and pipe in each room, the route to the exit and over the stair. |
| Exits and escape routes | A separate entrance is not required in every case. In a house at least five years old, exits are acceptable with any one of: a door directly outside serving only that unit; a shared exit enclosed by a 30-minute fire separation that does not pass through the other unit, with interconnected smoke alarms; an exit through the other unit plus a qualifying escape window and interconnected alarms; or sprinklers (Part 11, C139). | Which doors each unit will use to leave the house, and whether any route passes through the other unit. |
| Bedroom and escape windows | New-construction rule: each floor level with a bedroom needs an outside window that opens without tools to at least 0.35 m², with no dimension under 380 mm, and 550 mm clearance in a window well, unless a door on that level leads directly outside (9.9.10.1). An escape window that replaces a second exit (C139) must meet larger dimensions: 0.38 m² with no dimension under 460 mm, a sill no more than 900 mm above the floor and 1 m of clearance in a window well. | Sizes of the openable part of each window, sill heights and window wells, and which rooms will be bedrooms. |
| Natural light | New construction: glass equal to 10% of floor area for living and dining rooms and 5% for bedrooms; kitchens need no window where there is electric lighting (Table 9.7.2.3). Houses at least five years old may halve these where the window is not an exit (C110). | Room sizes and existing window glass areas. |
| Fire separation | New construction: walls and floor-ceiling framing between units covered with a continuous smoke-tight barrier of 15.9 mm Type X gypsum board, on both sides of walls and the underside of floor framing; the rating can be waived if the house is sprinklered (9.10.9.16.(4) and (5)). Houses at least five years old: 30-minute separation, or 15 minutes for floors where smoke alarms in every unit and common area are interconnected (C150, C156). | What the basement ceiling and walls are now (open joists, drywall or plaster), and what sits in the joist space, such as ducts and pipes. |
| Smoke and carbon monoxide alarms | Smoke alarms in each unit on every storey, in each bedroom, and in shared exits and common areas, with a visual signal, all interconnected (wired or wireless) so any alarm sounds throughout the house (9.10.19). CO alarms are needed where there is a fuel-burning appliance or an attached garage (Ontario (opens in a new tab)). | Where alarms are now, whether they are hard-wired, and whether the house has gas appliances or an attached garage. |
| Heating and ventilation | In a house at least five years old, one heating system may serve both units if each unit has smoke alarms and a smoke detector in the supply or return duct shuts off the furnace’s fuel and power when it activates (C201). Kitchens and bathrooms need ventilation. An HVAC permit may be needed (City (opens in a new tab)). | Whether you want to share the furnace or add a separate system, and where ducts run. |
| Plumbing | A shut-off valve where the water supply enters each unit, so either can be shut off without cutting the other (7.6.1.3.(5)). Plumbing and drain work is permitted with a Plumbing Data Sheet (City (opens in a new tab)). | Location of the drain stack and existing rough-ins, and whether the kitchen and bathroom will need a pump. |
| Electrical | Electrical work for a second unit needs a separate permit from, and inspection by, the Electrical Safety Authority (Ontario (opens in a new tab)). | The size and spare capacity of the electrical panel, and whether a separate panel or meter is planned. |
| Sound separation | In a house at least five years old, the separation between units needs sound-absorbing insulation, resilient channel and 12.7 mm gypsum board, or a tested STC 43 or ASTC 40 assembly (C181). | Whether the ceiling will be opened, since this work is done at the same time as the fire separation. |
Code references are to Division B of the 2024 Ontario Building Code; “C” numbers are Part 11 compliance alternatives in Table 11.5.1.1.-C, which apply to houses in existence for at least five years. The permit examiner decides how they apply to a specific design.
If the ceiling falls short and cannot be gained by moving ducts or pipes, the floor has to be lowered. The underpinning vs benching guide compares the two methods. Many basements need neither, so measure before assuming it.
Permits, inspections and closing the permit
- Confirm zoning and records. Check the zone, suite size and, for an existing suite, the permit history above. Zoning permits secondary suites as of right in the listed house types, so most projects need no separate zoning approval. A design that does not meet the zoning standards needs to be changed, or needs a zoning approval such as a minor variance before a permit can issue.
- Drawings. The City requires a site plan with a zoning summary, floor plans of every level showing existing and proposed uses, smoke and CO alarms and plumbing fixtures, sections showing floor-to-ceiling heights and stair details, and construction details. Drawings by a qualified designer must show the designer’s registration and qualification numbers (City permit guide (opens in a new tab)).
- Application. Apply online or by email with the permit application, Schedule 1 designer information and the Rental Renovation Licence Screening Form, which the City uses to decide whether a separate rental renovation licence is also needed (City (opens in a new tab)). Plumbing and HVAC permits can be added after the building permit application.
- Review. Express Services covers 1-to-2 unit conversions in a house with no more than two units and no active permit for a new house or addition. Heritage properties and projects needing variances are outside it (City (opens in a new tab)). The City aims to review eligible Express applications within 3 business days of intake (City (opens in a new tab)). The House Stream reviews complete applications within 10 business days, and a complete application there includes an issued Zoning Applicable Law Certificate (City (opens in a new tab)). These are review targets. Revisions requested by the examiner add time, and design work comes before them.
- Electrical permit. Obtained separately from the Electrical Safety Authority, usually by the licensed electrical contractor (Ontario (opens in a new tab)).
- Inspections. The City lists structural framing (with plumbing and HVAC rough-in), fire separations before interior finishes, insulation and vapour barrier, plumbing rough-in and final, HVAC rough-in and final, and a final interior inspection among the stages a house project may need. Inspections take place within two business days of a request (City (opens in a new tab)).
- Close the permit. Owners must book a final inspection. The City warns that open permits may impede future sales and permit applications (City (opens in a new tab)). Keep the permit, approved drawings and inspection results: they are the suite’s approval record.
A 60 m² (about 646 sq ft) area of work is an assumption for the arithmetic, not a typical suite.
Interior alterations: 60 m² × $11.53 = $691.80
New residential unit: $56.33
Building permit fee: $748.13
2026 rates from the City’s fee schedule (opens in a new tab), with a $214.79 minimum for all work. For renovations the area is the total area affected. Plumbing (per fixture) and HVAC permits are charged separately, and the ESA sets its own fees. Drawings and construction are not included.
What affects conversion cost?
The requirements above are also the main cost drivers. Price varies most with:
- The starting point. An unfinished basement needs everything; a finished one may need finishes removed to reach the ceiling for fire separation or to allow inspections.
- The kitchen and bathroom. Distance from the drain stack, and whether fixtures sit below the sewer and need a pump.
- Fire separation and alarms. Type X drywall across the whole ceiling, sealed openings and interconnected alarms throughout the house, including the upper unit.
- Exits and windows. A new exterior door, a below-grade entrance, or enlarged windows with window wells can each involve cutting the foundation.
- Systems. A second furnace or a duct smoke detector, extra ventilation, and panel or service upgrades.
- Structural work. Lowering the floor, removing a bearing wall or moving a beam adds engineering and a larger permit scope.
Explore Toronto basement apartment conversion permit values, including the full distribution and methodology.
Preparing to request a quote
Before contacting contractors, gather:
- A sketch or photos of the current layout, with room dimensions.
- Ceiling heights, including the lowest beams, ducts and pipes.
- Window sizes and sill heights, and the doors to the outside.
- Any permit records, drawings or a survey you already have.
- What you want to change: bedrooms, kitchen, bathroom, entrance, and whether the furnace and electrical service will be shared.
- For an existing suite, what was built when, as far as you know.
The measurement diagram shows where to take each measurement.
Ask each contractor to state who prepares the drawings and applies for the permits, which inspections their price covers, and what is excluded. The quote comparison guide covers allowances, taxes, payment milestones and changes.
Request a quote from one vetted contractor serving your Toronto area. Share your measurements, the current layout and what you want to build. If no contractor covers your postal code yet, Kildrin keeps your request and emails you when one does.
Request a basement apartment quote
Kildrin does not issue permits or confirm whether a suite is legal; the City does that through permits and inspections. Requesting a quote is free for homeowners. Participating contractors pay Kildrin for eligible introductions.
Other questions
Does a basement suite in a newer house follow the same rules?
Not entirely. The Part 11 compliance alternatives in the table apply only to houses in existence for at least five years (2024 Building Code, Div. A 1.3.3.3B (opens in a new tab)). A newer house generally follows the new-construction requirements, such as the Type X gypsum fire separation and the Part 9 exit rules. The ceiling-height minimums are the same in both.
Can I prepare the drawings myself?
The City’s Schedule 1 form covers designers and lets a property owner who is exempt from the qualification requirements state the reason for the exemption (City permit guide (opens in a new tab)). The drawings still have to show everything the City lists, and any structural change may need an engineer.