What your basement needs to become a legal unit.
Not every basement can become a second suite as-is, but most can get there with the right changes. Five things decide it: ceiling height, a proper egress window, fire separation from the rest of the house, a livable floor plan, and a way in that doesn’t require walking through someone else’s home.
Grab a tape measure. See where you stand.
- Ceiling heightClears the 1.95 m ceiling height.Meets it
- Egress window0.27 m² is under 0.35 m². A larger window and well.Needs work
- Bedroom floor areaMeets the 7 m² bedroom minimum.Meets it
- Second entranceA way in that skips the other unit’s living space.Meets it
- Fire separationRated drywall, a rated door and sealed penetrations, plus linked alarms.Added in the build
Typical minimums, not a ruling. Municipal review confirms the number for your basement.
Most projects fail on one of three things.
- 01
Too low
Ceiling height is the first filter.
- 02
No good exit
Bedrooms may need a proper egress path.
- 03
Poor layout
The space still has to work as a home.
What each one actually means.
Source: Ontario Building Code (O. Reg. 163/24), 2024 compendium, Division B: ceiling heights in 9.5.3.1, bedroom areas in 9.5.3D, egress windows in 9.9.10.1, suite fire separations in 9.10.9.16 and the Part 11 compliance alternative C156 for existing houses, as of October 2026. Municipal review confirms the number that applies to your basement.
- 01
Ceiling height
Clear height in the finished living space.
Typical minimum1.95 m (6′5″) ceiling height; 1.85 m (6′1″) clear under beams and ducts.
- 02
Egress window
On every floor level with a bedroom, at least one window big enough to climb out of in a fire, unless a door on that level leads straight outside.
Typical minimumAn unobstructed opening of at least 0.35 m² (3.77 sq ft), no side smaller than 380 mm, with 550 mm of clear space in front.
- 03
Fire separation
A fire-rated wall and ceiling assembly between the basement unit and the rest of the house.
Typical minimum45 minutes, or a continuous 15.9 mm Type X drywall barrier. In an existing house, 30 minutes, or 15 minutes for the floor with interconnected smoke alarms.
- 04
Bedroom floor area
Minimum floor area per bedroom.
Typical minimum7 m² (6 m² with built-in closets), and at least one bedroom of 9.8 m² (8.8 m² with built-ins).
- 05
Second entrance
A way in and out that doesn’t pass through the other unit’s living space: an existing side or rear door, or a new one.
Typical minimumA separate exterior door, or a shared interior hallway that doesn’t cut through anyone’s living space.
How high does a basement ceiling need to be?
At least 1.95 m (6′5″), with 1.85 m (6′1″) of clear height allowed under beams and ducts. Ceiling height is the single biggest reason a basement doesn’t qualify without work. A basement poured to modern standards usually clears the 1.95 m bar without trouble. Older houses, especially ones built before the 1980s, often don’t, and the fix (underpinning, to lower the basement floor) is expensive enough that it changes the entire budget conversation.
What exit and fire safety does a basement suite need?
An egress window on every floor level with a bedroom, and a fire separation between the units with interconnected smoke and CO alarms. They’re the two requirements people underestimate.
Can someone get out quickly?
A basement with bedrooms needs a way out that isn’t the stairs: at least one egress window on that level, unless a door there leads straight outside. Most older basement windows are too small, too high, or both, so the wall usually needs to be cut open for a proper window well and a larger window. It’s non-negotiable: a bedroom level without a compliant egress window or exterior door won’t pass inspection.
Bigger than “there is a window.”Can fire stay contained?
Once a basement becomes its own legal unit, a fire in one unit can’t spread into the other undetected. That’s what fire separation buys: fire-rated drywall, a fire-rated door where the units meet, and every penetration (plumbing, electrical, ducting) sealed. Combined with interconnected smoke and CO alarms on every level of both units.
Details around ducts and wiring matter too.New to the terms? See egress window and fire separation in the glossary.
A good basement is only step one.
This page is about the physical basement itself. It doesn’t cover whether your lot is zoned for a second unit, parking, or servicing. Those depend on your specific property and municipality, not the basement’s condition.
Common questions.
What is the minimum ceiling height for a legal basement apartment in Ontario?
The Ontario Building Code (9.5.3.1) requires a ceiling height of at least 1.95 m (6′5″) in a secondary suite, with at least 1.85 m (6′1″) of clear height under beams and ducts.
Does every basement bedroom need its own egress window?
No. The Ontario Building Code (9.9.10.1) requires at least one egress window on every floor level that has a bedroom, unless a door on that level leads directly outside. The window must open from the inside without tools, give an unobstructed opening of at least 0.35 m² with no side under 380 mm, and have 550 mm clear in front if it opens into a window well.
Pick the question closest to yours.
Does my property qualify?
Zoning, parking and servicing, not just the basement.
Basement Apartment vs. Garden Suite
Cost, timeline, zoning path and servicing, compared side by side.
Cost & Financing
What drives the build cost, plus HELOC, loans and municipal grants.
We’ll walk it and tell you exactly.
Ceiling height, egress, fire separation and layout, checked on site before you spend anything on drawings.