Key Takeaways
- Bedroom windows below grade must be large enough to escape through in a fire — code sets a minimum opening of 0.35 m².
- Many basement “bedrooms” I inspect fail this and can’t legally be advertised as bedrooms.
- If you’re finishing a basement, confirm egress sizing before framing — adding it after the fact is expensive.
- This applies to any room used for sleeping, regardless of how it’s listed.
A bedroom window is not just for light and fresh air. In a fire, when the hallway is impassable, it may be the only way out — or the only way for a firefighter to get in. That’s why the National Building Code sets minimum size requirements for bedroom windows: they need to be functional emergency exits, not just appropriate holes in the wall.
What the code requires
The National Building Code of Canada requires that every bedroom — except in sprinklered suites — have at least one outside window or exterior door that is openable from the inside without the use of keys, tools, or special knowledge, and without removing screens or hardware. The unobstructed opening must meet all of the following minimums:
- Minimum opening area: 0.35 m² (542 square inches — about 3.76 square feet)
- Minimum opening height: 380 mm (15 inches)
- Minimum opening width: 380 mm (15 inches)
- Maximum sill height above floor: 1,500 mm (about 5 feet) — so you can actually reach and climb through it
These are opening dimensions — the clear unobstructed space when the window is fully open, not the rough frame or glass size. A window that looks large but has a small operable sash may not comply. The opening must also stay open on its own during an emergency without needing to be held.
When a sill is higher than 1.5m above the floor (common in basement bedrooms), access to the window needs to be improved by some means — built-in furniture, a permanent step, or a window well ladder.
Not all window types are equal for egress
Casement windows are generally the best option for egress, especially in basements. Because the hinged sash swings fully clear of the opening, even a relatively small casement can meet the 0.35m² requirement. Some manufacturers offer special operator arms that push the window wider than the standard mechanism allows — useful where space is tight. These are a popular choice for basement egress retrofits.
Double-hung windows are more challenging. When fully open, the sliding sashes overlap, meaning more than half the overall window area is blocked. To achieve a compliant egress opening, a double-hung window needs to be significantly larger than a casement of the same rough opening size. Many older double-hung windows in bedroom locations don’t comply for this reason.
Gliding (sliding) windows face the same problem as double-hungs — the sash always occupies half the opening area, so the window needs to be quite large to meet the 0.35m² requirement.
Awning windows generally make poor egress windows. The outward-swinging sash impedes both entry and exit, and standard operating hardware often gets in the way. Only awning windows fitted with special detachable operator hardware can meet egress requirements.
Height vs. width when retrofitting: If you’re enlarging a window opening to meet egress, increasing the height is almost always less work than increasing the width. Widening an opening requires a larger structural header above — a significant project. Lowering the sill is comparatively straightforward.
Where egress windows most often fall short
Basement bedrooms are the most common problem area. Older homes were built with small, narrow basement windows appropriate for a storage room — not a sleeping space. When basements get finished and bedrooms added, those original windows are frequently left in place. Sleeping in a room with a window you can’t escape through is a life-safety issue, full stop.
Replacement windows are another common culprit. Homeowners sometimes choose replacement units with a smaller operable sash than the original — to reduce drafts, or simply because it was cheaper. The new window fits the rough opening, but the clear egress area no longer complies. I see this regularly, especially in bedrooms where windows were replaced without a permit.
Window wells for basement egress
A compliant egress window in a basement is only half the picture — the window well outside needs to allow someone to actually climb out. The well should be large enough to open the window fully and provide clear space to manoeuvre. A ladder is required if the well is more than 44 inches deep. Well covers are acceptable for keeping out debris and pests, but must be easily openable from the inside without tools or keys.
What I look for on an inspection
In every bedroom, I measure the operable window opening and check the sill height. In basement bedrooms, I also assess the window well. When a window doesn’t meet egress requirements, it goes in the report as a life-safety finding — not optional, not "monitor and maintain." If you’re sleeping in that room, the window is a problem that needs to be addressed.
If you’re finishing a basement: Egress windows are not optional. Budget for them before you frame the bedrooms, not after. Retrofitting around finished walls is significantly more expensive and disruptive. And if you’re buying a home with a finished basement, make sure any bedrooms down there have compliant egress — it’s one of the first things I check.
For a detailed reference on egress window requirements, including a size chart for compliant height/width combinations, see the Egress Windows Information sheet (PDF) I keep on hand for clients.