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Code & Safety
Building Code Reference
Key residential stair code requirements (IRC 2021). Always verify with your local building department.
7-3/4" max
All risers must be within 3/8" of each other. Measured vertically from tread to tread.
10" minimum
Measured horizontally from nosing to nosing. Nosing not included in this measurement.
3/4" – 1-1/4"
Nosing must project beyond the riser face. Variation between nosings: 3/8" max.
34" – 38"
Measured vertically from the stair nosing to the top of the handrail.
36" minimum
Required at open sides where drop exceeds 30". Commercial: 42" minimum.
4" sphere rule
No opening can allow a 4" diameter sphere to pass through.
36" minimum
Clear width at and below handrail height. Handrails can project up to 4.5" each side.
6'8" minimum
Measured vertically from the sloped plane of nosings to the ceiling above.
Important Notes
- •These are general IRC guidelines. Local jurisdictions may have stricter requirements.
- •Commercial buildings follow IBC codes, which differ from residential IRC codes.
- •Always verify requirements with your local building department before starting work.
- •Permits may be required for new construction or major modifications.
- •ADA accessibility requirements apply to public and commercial spaces.
