Stair Rise and Run Requirements
Last updated: June 2026
Maximum rise, minimum run, and uniformity rules for residential stairs.
Detailed explanation
OBC Part 9 limits the rise of a step and requires a minimum run (tread depth) for stairs in dwelling units. Rise and run must be uniform within a flight — variation can create trip hazards and fail inspection.
Private stairs (serving a single dwelling unit) have different limits than stairs used in public areas or as required exits. Always identify the stair type before applying dimensions.
Winders and curved stairs have additional rules. Measure rise and run at the walk line, not at the inner edge of the tread.
Ontario Building Code references
Ontario Building Code
Section 9.8.3. — Rise and run
Dimensional limits for steps.
Ontario Building Code
Section 9.8.4. — Stairs
Construction and uniformity requirements.
Examples
- A main-floor-to-second-floor stair in a house must meet Part 9 rise and run limits.
- Basement stairs that are not the principal entrance may qualify as private stairs with different limits.
Common mistakes
- Mixing rise dimensions within a single flight.
- Measuring run at the narrow inside edge of a winder instead of the walk line.
- Applying public-stair limits to a private stair without verifying classification.
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