What are the egress window requirements for a basement bedroom under Ontario Building Code?

Every basement bedroom in Ontario must have an egress window that provides a minimum unobstructed opening of 3.77 square feet (0.35 square metres), with a minimum width of 15 inches (380 mm) and a maximum sill height of 44 inches (1,100 mm) from the finished floor. These are non-negotiable life-safety requirements under the Ontario Building Code — without a compliant egress window, the room cannot legally be designated as a bedroom, and more critically, occupants cannot escape during a fire or emergency when interior routes may be blocked by smoke and flames.

The 3.77 square foot minimum opening refers to the clear, unobstructed area when the window is fully open — not the overall window frame size or the glass area. This is an important distinction because many window styles have frames, hardware, and opening mechanisms that reduce the usable opening significantly below the overall window dimensions. When shopping for egress windows, always verify the clear opening specification in the manufacturer's data, not just the rough opening or frame dimensions. A window that looks large enough when closed may not provide the required 3.77 square feet when opened.

The maximum sill height of 44 inches from the finished floor ensures that occupants — including children, elderly family members, and people with limited mobility — can reach and climb through the window during an emergency. If your basement has a low ceiling and you're mounting the window high on the wall to maximize its position above grade, measure carefully from the finished floor (including whatever flooring you're installing) to the top of the sill. If the sill exceeds 44 inches, the window must be lowered in the foundation wall, which may require cutting more concrete.

Installing an egress window in an existing GTA basement is a significant construction project because it involves cutting a large opening in the foundation wall — typically a poured concrete or concrete block wall that is 8 to 12 inches thick. This requires specialized concrete cutting equipment, careful attention to any reinforcement steel in the wall, and a structural assessment to ensure the opening doesn't compromise the foundation's load-bearing capacity. A structural lintel (typically a steel angle or reinforced concrete beam) must be installed above the opening to transfer the load around the window. The cost for a single egress window installation in the GTA, including cutting the foundation, installing the window, constructing the window well, and backfilling, ranges from $3,000 to $8,000 depending on the wall thickness, window size, and site access conditions.

Window wells are required for below-grade egress windows to provide the clear space needed for escape and firefighter access. The window well must be large enough to allow the window to open fully and for a person to climb out. If the window well is deeper than 24 inches below grade, a permanently attached ladder or steps must be provided to allow occupants to climb out of the well. Window well covers are permitted but must be operable from inside without tools or special knowledge — a cover that requires removing screws or clips from the outside defeats the purpose of the egress window.

The City of Toronto building inspector will verify egress window compliance during the permit inspection process, measuring the clear opening, sill height, and window well dimensions. This is one inspection item where there is zero tolerance for non-compliance — if the window doesn't meet the minimums, the room cannot be approved as a bedroom until it's corrected.