You need one egress window for every bedroom in a basement, not one for the whole basement. If a basement has two bedrooms, it needs two compliant egress windows or exterior doors, one serving each room, unless a walkout door already provides a direct exit from that bedroom.
- Ontario code ties egress windows to bedrooms, so the count depends on how many basement bedrooms you have.
- A basement with one bedroom needs one egress window; two bedrooms need two.
- Shared basement spaces like a rec room or hallway do not need their own egress window.
- A walkout door straight to grade can replace the need for a window in that specific bedroom.
- Each window must give a clear opening of at least 0.35 m², with no side under 380 mm.
Why Does the Count Depend on Bedrooms, Not Square Footage?
Ontario’s egress rule is written around sleeping rooms, not total basement area. That means the number of required egress windows equals the number of legal bedrooms in the basement, since each one needs its own independent way out in an emergency.
This surprises a lot of homeowners who assume a big open basement needs several egress windows regardless of layout. A large unfinished basement with no bedrooms technically needs none, while a small basement apartment with two bedrooms needs two, one per room.
The Rule Behind the Number
Under Ontario Building Code section 9.9.10.1, every floor level containing a bedroom in a suite needs at least one outside window or door that opens from the inside without tools and gives a clear opening of at least 0.35 square metres, with no dimension under 380 millimetres. This applies floor level by floor level, and a basement counts as its own floor level.
If your basement has one bedroom, that room needs one compliant window. Add a second bedroom on the same level, and that room needs its own separate window too, since one window cannot serve two bedrooms at once.
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How Does This Apply to Basement Apartments and Legal Second Suites?
Basement apartments in the GTA are under close scrutiny after recent fires linked to blocked or missing exits, so this rule gets enforced strictly for legal second suites. Each bedroom in a basement rental unit needs its own egress window or exterior door, and the path from the bedroom to that window cannot pass through a furnace room, storage area, or other hazard zone.
“We see a lot of basement conversions where someone squeezed in a second bedroom but only ever budgeted for one egress window,” says a lead installation manager at TotalSeal. “That is one of the fastest ways to fail a building inspection on a basement apartment.”
| Basement Layout | Egress Windows Needed |
| Unfinished basement, no bedrooms | None required |
| One basement bedroom | One |
| Two basement bedrooms, same level | Two, one per bedroom |
| One bedroom with a walkout door to grade | None, if the door meets exit rules |
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What Window Well Requirements Come With the Count?
Each egress window that opens into a window well needs 550 millimetres of clearance in front of it, so a person has room to climb out fully, under the same code section covered above. If the well is deeper than about 600 millimetres, it also needs a permanent ladder, and any cover over the well must open from inside without keys or tools.
These well requirements apply per window, so two egress windows in a basement mean two wells to plan for, each with its own clearance and drainage.
Pros and Cons of Adding a Second Basement Bedroom
Pros
- Adds rental income potential or extra family living space.
- Increases resale value when done to legal standard.
- Brings more natural light and air into the basement overall.
Cons
- Doubles the egress window and window well cost.
- Needs a building permit and inspection to be legal.
- Requires enough ceiling height and floor area to meet code for a bedroom.
“Every basement egress window we install has to hit that 0.35 square metre clear opening exactly, and cutting corners on size is the number one reason basement conversions fail inspection,” says a senior product engineer at TotalSeal. “Multi-chamber vinyl frames built for basement hopper windows are sized to meet this rule while still holding up against below-grade moisture and cold.”
What Mistakes Do Homeowners Make?
A frequent mistake is assuming one large egress window can serve two separate bedrooms if they share a wall, which it cannot under the floor-level rule. Another is forgetting the window well clearance and ladder requirement once the window itself is sized correctly. Homeowners also sometimes skip the permit for a basement egress window, not realising that a permit is required whether you are enlarging an existing opening or cutting a brand new one.
Planning a Basement Bedroom the Right Way
If you are planning a basement bedroom, whether for family use or a legal rental unit, count your bedrooms first and plan one egress window per room from the start. Retrofitting an egress window after drywall and flooring are finished costs significantly more than building it into the plan from day one.
Frequently Asked Questions
Does a basement rec room need an egress window?
No. Egress windows are required for bedrooms specifically, not for recreation rooms, laundry rooms, or other non-sleeping basement spaces.
Can two basement bedrooms share one egress window?
No. Each bedroom needs its own independent egress window or exterior door; one window cannot serve two separate sleeping rooms.
What size does a basement egress window need to be?
At least 0.35 square metres of clear opening, with no dimension smaller than 380 millimetres, measured on the actual operable portion.
Do I need a permit to add a basement egress window?
Yes. A building permit is required whether you are enlarging an existing window opening or cutting a new one into the foundation.
Can a walkout basement door replace an egress window?
Yes, if the door opens directly to grade and the path to it does not pass through a furnace room or other hazard area.
If you are planning a basement bedroom or apartment, our contact us page is the quickest way to get a code-compliant egress window quote for your specific layout.
