What does a legal basement apartment need in Ontario?

A legal basement apartment in Ontario needs a building permit and has to be built to the 2024 Ontario Building Code: ceilings of at least 1.95 m, a fire separation between the two units, smoke alarms linked through the whole house, and an escape window or door on every floor with a bedroom. Your town sets the zoning, and as of October 2026 every lower-tier town in Durham Region, Ontario allows at least one unit in the house, and several, Whitby and Pickering among them, make you register it.

Key takeaways

• Ceilings in a secondary suite must be at least 1.95 m, and 1.85 m under beams and ducts, under Div. B 9.5.3.1. of the 2024 Building Code Compendium.
• The units are separated by a 45-minute fire separation, or in a house with one secondary suite by 15.9 mm Type X drywall on both sides of walls and under the floor framing (9.10.9.16., Building Code).
• Every bedroom level needs a window with an opening of at least 0.35 m² and no side under 380 mm, unless a door on that level leads outside (9.9.10.1., Building Code).
• On urban residential land, the Planning Act stops a town from prohibiting three units on a lot or requiring more than one parking space per added unit.
• Whitby charges $268 to register an additional dwelling unit under By-law 8156-25, per the Town's ADU page.

What makes a basement apartment legal in Ontario?

A basement apartment is legal when three things line up: zoning allows the unit, a building permit was issued and closed with final inspections, and the unit is registered where the town requires it. A finished basement with a kitchen and a side door isn't legal on its own, however good the finish looks.

The permit matters even if you build nothing new. Section 10 of the Building Code Act requires a permit to change the use of a building where the change increases the hazard, and turning one dwelling into two does that. Electrical work in the new unit has to be done by a Licensed Electrical Contractor, who files a notification with the Electrical Safety Authority before starting. A new gas line or appliance needs a TSSA-registered gas contractor under O. Reg. 212/01.

One definition shapes everything else. The Code defines a secondary suite as a self-contained unit in a building that holds only one other dwelling unit plus common spaces (Div. A 1.4.1.2.). Most of the easier rules below apply to a "house with a secondary suite". If you plan a third unit in the same house, it's no longer that kind of building and stricter rules start to apply, so talk to your building department early. Our Bill 23 guide covers how many units your town allows.

What does the Ontario Building Code require for a basement apartment?

As of October 2026, these are the Code rules homeowners ask about most, all from the 2024 Building Code Compendium (O. Reg. 163/24):

Note: this is a summary of the most-asked articles, not the whole Code; your permit drawings have to cover every article that applies, and the building department reviews them.

Ceiling height

The 1.95 m rule is the one that decides many basements. For comparison, an ordinary finished basement in a single-family house only needs 2,100 mm over 75% of the basement area, dropping to 1,950 mm under beams and ducts (Table 9.5.3.1.). The suite figure is lower, and the parts of each room that meet it have to connect to the room's entry (9.5.3.1.(4)); ask your building department how they'll measure your rooms. If your joists sit too low, the options are lowering the floor by underpinning or bench footings, or moving ducts. Our cost guide has our price ranges.

Fire separation

Many two-unit conversions use the drywall route in Sentence (4): a continuous, smoke-tight layer of 15.9 mm Type X on both sides of the walls between units and on the underside of the floor framing above the basement. The word that matters is "continuous". Pot lights, duct runs and the furnace room all break the layer unless they're detailed properly. In a sprinklered house the rating can be waived (9.10.9.16.(5)).

Escape windows and smoke alarms

Each floor with a bedroom needs one escape window, sized as in the table, unless a door on that level opens straight outside. The 1,000 mm maximum sill height doesn't apply in basements, but a window opening into a well needs 550 mm of clear space in front of it (9.9.10.1.(2) and (3)). Smoke alarms in both units have to be linked so an alarm in the basement sounds upstairs, and the reverse (9.10.19.5.(2)).

The way out

The suite's route to the exit can't pass through the other unit or a service room such as a shared furnace room (9.9.7.5.(1)). That's why a separate entrance, or a shared vestibule that belongs to neither unit, is the usual answer. The federal tax credit for a family suite separately requires a private entrance, which we cover in the cost guide.

What do Durham towns allow and require?

The Planning Act sets a floor, and each town's zoning by-law fills in the details: parking, path to the entrance and registration. As of October 2026, here's what the five lakeshore towns publish:

Note: these are zoning summaries for typical urban lots as of October 2026; hazard lands, Moraine and Greenbelt lots and site-specific zoning can change the answer for your property.

Whitby also requires an unobstructed path to the unit's entrance at least 1.2 m wide and 2.1 m high, per By-law 1784. Pickering's by-law asks for a 1.2 m path from each unit's entrance to the street. A side-yard entrance on a narrow lot can fail this test before the Building Code even comes into it, so measure the side yard first.

Provincial law limits what a town can demand. On urban residential land, meaning a settlement area on municipal water and sewer, the Planning Act bars zoning that requires more than one parking space per added unit or sets a minimum unit size. O. Reg. 299/19 lets anyone live in the unit, related or not, and allows it whatever the age of the house.

Do you have to register a basement apartment in Durham Region?

You do in Whitby, Pickering, Scugog and Uxbridge. Whitby's registration by-law, 8156-25, charges $268, or $534 if the Town finds the unit through a complaint, per its ADU page. Pickering makes registration with its Building and Fire Services mandatory under By-law 8040/23, per Pickering's ADU page; we didn't find the fee published there. Scugog requires registration before anyone moves in, per its ADU page, and Uxbridge asks owners to register two-unit houses through its secondary suites page.

Oshawa issues a two-unit house registration as part of the building permit, per its accessory apartments page. We found no current registration program in Ajax and none published by Clarington, as of October 2026. If you're in Whitby and building now, the Town's incentive needs the unit registered by 31 March 2027; see our Whitby ADU incentive guide. The permit itself, fees and timelines are in basement permits in Durham Region.

How we approach a basement apartment

We're Jarvis Contracting, a family design-build firm based in Ajax. James Jarvis runs construction and his wife, Ceara Jarvis, runs design through her studio Juliette Interiors. We draw permit drawings in-house and build basements and additional units. We plan, draw and build to the Ontario Building Code; the town's building department reviews the drawings and inspects the work.

The first visit is a tape measure, not a mood board: joist height, duct runs, the foundation wall where an entrance could go and the side-yard width for the path. Those four measurements show if you're looking at a straightforward suite or an underpinning job. Read more on our basement renovations page.

Questions

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

The minimum ceiling height for a basement apartment in Ontario is 1.95 m, with 1.85 m allowed under beams and ducts, under Div. B 9.5.3.1. of the 2024 Building Code. The areas that meet it have to connect to the room's entry. If your basement is lower, the usual fixes are lowering the floor or moving ductwork.

Does a basement apartment need its own entrance in Ontario?

The Building Code says a basement apartment's route to the exit can't pass through the other unit or a service room (9.9.7.5.). In practice that means a separate entrance or a shared vestibule that belongs to neither unit. The federal Multigenerational Home Renovation Tax Credit separately requires a private entrance.

Do basement bedrooms need an egress window in Ontario?

Basement bedrooms do need an escape route in Ontario. Every floor level with a bedroom needs at least one window that opens from inside without tools, with an opening of at least 0.35 m² and no dimension under 380 mm, unless a door on that level leads directly outside. A window that opens into a well needs 550 mm of clear space in front of it.

What fire separation does a basement apartment need?

The default is a 45-minute fire separation between units. In a house with one secondary suite, the Code allows a continuous, smoke-tight layer of 15.9 mm Type X drywall on both sides of the walls between the units and under the floor framing instead (9.10.9.16.(4)). In a sprinklered house the rating can be waived.

Do I have to register a basement apartment in Whitby?

As of October 2026, Whitby requires every additional dwelling unit to be registered under By-law 8156-25, for a $268 fee, or $534 if the Town finds the unit through a complaint. Registration is also a condition of Whitby's ADU incentive, which needs the unit registered by 31 March 2027.

Can my basement apartment be rented to someone who isn't family?

A basement apartment can be rented to anyone. Ontario Regulation 299/19 lets anyone live in an additional residential unit, related to the owner or not. The federal tax credit for a family suite is the exception: it only applies when the unit houses a senior or a disabled adult relative.

Sources

1. 2024 Ontario Building Code publications.gov.on.ca
2. Planning Act ontario.ca
3. Town's ADU page whitby.ca
4. Building Code Act ontario.ca
5. Electrical Safety Authority esasafe.com
6. O. Reg. 212/01 ontario.ca
7. Whitby Zoning By-law 1784, s.4 media-003-ca.cdn.govstack.com
8. Oshawa accessory apartments page oshawa.ca
9. Ajax Zoning By-law 95-2003, s.4.4 ajax.ca
10. Pickering Zoning By-law 8149/24 corporate.pickering.ca
11. Clarington ADU page clarington.net
12. O. Reg. 299/19 ontario.ca
13. Pickering's ADU page pickering.ca
14. ADU page scugog.ca
15. secondary suites page uxbridge.ca