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 1.95 m in the main areas.Meets it
- Egress window0.27 m² is under 0.35 m². A larger window and well.Needs work
- Bedroom floor areaRoomy enough for a bedroom.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.
Directional figures, gathered from public building-industry sources rather than quoted from the code itself. Treat them as a strong starting point, not a final answer. 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″) in main areas; 1.85 m (6′1″) often allowed under beams and ducts.
- 02
Egress window
A window in every bedroom big enough to climb out of in a fire, and for a firefighter to climb in.
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 minimumCommonly a 30-minute rating for existing-house conversions.
- 04
Bedroom floor area
Minimum livable space per bedroom, excluding closets.
Typical minimumRoughly 7 m² (75 sq ft).
- 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.
Ceiling height, first.
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.
Exit and fire safety.
The two requirements people underestimate.
Can someone get out quickly?
Every basement bedroom needs its own way out that isn’t the stairs. 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 without a compliant egress window 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.
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.