What is the minimum egress window opening size for a basement bedroom?
Minimum Egress Window Size for a Basement Bedroom in Canada
Every bedroom in an unsprinklered dwelling unit must have at least one operable window or exterior door providing emergency escape, and for basement bedrooms the rules are especially important because fire can cut off the only interior exit route.
Core Size Requirements
Under the National Building Code, the escape window must provide an unobstructed open portion with a minimum area of 0.35 m2 (3.76 ft2), and no dimension of that opening can be less than 380 mm (15 in.) [Source: NBCC 2020 Illustrated Users Guide - Part 9 Div B, Page 137, Section 9.9.10.1]. A critical planning note: a window opening that is exactly 380 mm by 380 mm (15 in. by 15 in.) produces an area of only 0.144 m2 (1.55 ft2), which does not satisfy the minimum area requirement [Source: National Building Code of Canada - 2020, Page 1355, Section A-9.9.10.1.(2)]. Both the minimum dimension in every direction and the minimum area must be met simultaneously.
The window must be openable from the inside without tools, and it must stay open without manual support [Source: NBCC 2020 Illustrated Users Guide - Part 9 Div B, Page 137, Section 9.9.10.1].
Basement-Specific Rules
For a basement bedroom specifically, the egress window or door must be located within the bedroom itself. Relying on a window elsewhere in the basement is not acceptable [Source: National Building Code of Canada - 2020, Page 1355, Section A-9.9.10.1.(1)].
Where the window opens into a window well, a minimum clearance of 760 mm (30 in.) must be maintained in front of the window to allow a person to manoeuvre outward and upward [Source: National Building Code of Canada - 2020, Page 1355, Section A-9.9.10.1.(3)]. No extra clearance beyond the 760 mm (30 in.) is needed for slider, casement, or inward-opening awning windows, but outward-opening awning windows require additional depth so the 760 mm (30 in.) is measured beyond the outer edge of the open sash [Source: NBCC 2020 Illustrated Users Guide - Part 9 Div B, Page 137, Section 9.9.10.1]. Hopper (bottom-hinged) windows should not be used as egress windows where occupants would have to climb over the glass [Source: National Building Code of Canada 2025, Page 1474, Section A-9.9.10.1.(3)].
Sill Height
The code does not set a maximum sill height, but it is recommended that the sill be no higher than 1.5 m (4 ft. 11 in.) above the floor. Where this is unavoidable, built-in furniture installed below the window is a recommended solution to improve access [Source: National Building Code of Canada - 2020, Page 1355, Section A-9.9.10.1.(2)].
Provincial Difference: Ontario
Ontario's 2024 Building Code specifies a reduced window well clearance of 550 mm (21 5/8 in.) rather than the 760 mm (30 in.) required by the NBC and most other provinces [Source: Ontario Building Code 2024 — Volume 2, Page 202, Section A-9.9.10.1.(3)]. All other sizing requirements (0.35 m2 minimum area, 380 mm minimum dimension) remain consistent with the national model code. Designers working in Ontario should apply the 550 mm (21 5/8 in.) window well clearance.
Exemption
The egress window requirement does not apply where the dwelling unit is sprinklered or where the bedroom has a direct doorway to the exterior [Source: NBCC 2020 Illustrated Users Guide - Part 9 Div B, Page 137, Section 9.9.10.1].
Sources cited
NBC-GUIDE • 2020 • p. 137 • §Section 9.9.10.1
NBC • 2020 • p. 1355 • §Section A-9.9.10.1.(2)
NBC • 2020 • p. 1355 • §Section A-9.9.10.1.(1)
NBC • 2020 • p. 1355 • §Section A-9.9.10.1.(3)
NBC • 2025 • p. 1474 • §Section A-9.9.10.1.(3)
OBC-2024-V2 • 2024 • p. 202 • §Section A-9.9.10.1.(3)
This answer is AI-generated from the cited sources. While CodesWise grounds every response in the official code documents, you remain responsible for verifying the requirements that apply to your specific project. Always confirm against the authoritative code for your jurisdiction.