Basement Stairs — Code Considerations
Last updated: June 2026
Headroom, width, egress, and fire separation for basement stairways.
Detailed explanation
Basement stairs must maintain minimum headroom along the entire path. Reduced headroom at the bottom of a run is a common inspection failure.
If the basement contains a secondary suite or sleeping area, the stair may become part of a required egress path and trigger stricter width, fire separation, or exit requirements.
Open stairs versus enclosed stair shafts affect fire separation and smoke movement. Enclosing a basement stair with rated construction may be required depending on layout.
Ontario Building Code references
Ontario Building Code
Section 9.5.2. — Headroom
Minimum headroom in exits and stairways.
Ontario Building Code
Section 9.8.2. — Stairways
Stairway requirements in Part 9.
Examples
- Renovating a basement for a legal apartment may require upgrading the existing stair width or enclosure.
- Low ductwork under a basement stair run can reduce headroom below the minimum.
Common mistakes
- Assuming an existing basement stair meets egress for a new secondary suite.
- Ignoring headroom at the underside of the lowest tread or landing.
- Blocking required egress with storage at the bottom of basement stairs.
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