If you are finishing a basement and adding a bedroom, the window is not a detail you can leave to the end. It is a code requirement, it usually needs a permit, and it is the item most likely to fail an inspection after the drywall is up.
The numbers
The National Building Code sets the baseline for a bedroom window used as an emergency exit. Provinces adopt it with their own amendments, so treat these as the floor and confirm locally:
- At least 0.35 m² (roughly 3.8 sq ft) of unobstructed openable area
- No dimension less than 380 mm (about 15 in)
- Openable from the inside without tools, keys or special knowledge
- A sill height reachable from the floor — many jurisdictions set roughly 1,500 mm as the maximum
Two traps catch people. First, the requirement is the clear opening, not the rough opening — frame thickness and the sash itself eat into it, and a thicker triple-glazed frame can push a unit that used to pass below the minimum. Second, if the window opens into a window well, the well needs clear space in front of it, commonly 550 mm.
When you need a permit
Replacing a basement window with the same size unit generally does not require a permit. Enlarging the opening to meet egress almost always does, because cutting a wider opening in a foundation wall is structural work. Expect the application to want drawings, and expect an inspection.
This is the single most common way a homeowner trips a permit requirement without realising it — the job feels like a window swap and is legally a structural alteration. Municipal rules and fees vary widely: some cities charge by construction value, others have a flat fee, and a few require a permit for any window work at all. Each of our city pages carries the local rule — Regina, Calgary and Winnipeg are good places to start if you are on the prairies.
What it costs
- Same-size basement window replacement — $600 to $1,400
- Enlarging an opening in a poured foundation — $2,500 to $6,000, including cutting, lintel, window and finishing
- New window well with drainage — $1,500 to $4,000
- Permit — typically $100 to $400, depending on how your municipality prices it
Concrete cutting is the variable. A poured wall costs more than block, and depth, access and whether the excavator can reach the wall all move the number.
Worth doing properly
An egress window is a life-safety item, so this is not the place to save money on the install. Insist on a proper lintel, drainage at the base of the well tied into weeping tile, and a cover rated to be opened from inside if you fit one. Get the permit — an unpermitted bedroom can surface as a problem at sale, at insurance-claim time, or both.
If you are also replacing windows elsewhere in the house, our cost guide and vinyl versus fibreglass comparison will help you spend the budget where it matters.