Stair Building Code Dimensions
Doors & Walls · 8 specs
Direct Answer
Residential stair construction is strictly regulated under the International Residential Code (IRC Section R311.7) and OSHA into mandatory geometric limits: maximum 7-3/4 inch (197 mm) riser height, minimum 10 inch (254 mm) tread run depth, 36 inch minimum width, 6'8" headroom, and 34–38 inch handrail height.
Source: International Residential Code (IRC) Section R311.7 / IBC Section 1011 / OSHA 1910.25 (Stairways) · Last reviewed Aug 28, 2026
Specs
| Governing Standards | IRC Section R311.7 (Residential) / IBC Section 1011 (Commercial) / OSHA 1910.25 |
| Maximum Riser Height | 7-3/4 inches (197 mm) IRC Residential | 7.0 inches (178 mm) IBC Commercial |
| Minimum Riser Height | 4.0 inches (102 mm) | Prevents tripping from unexpectedly shallow steps |
| Minimum Tread Run Depth | 10.0 inches (254 mm) IRC with nosing | 11.0 inches (279 mm) IBC Commercial |
| Maximum Riser / Tread Tolerance | Maximum 3/8 inch (9.5 mm) variance between the tallest and shortest riser in a single flight |
| Minimum Stairway Clear Width | 36 inches (914 mm) clear width above handrail height (IRC R311.7.1) |
| Minimum Vertical Headroom | 6 feet 8 inches (2032 mm / 80 in) measured vertically from the sloped tread nosing line |
| Handrail Height Standard | 34 to 38 inches (864 to 965 mm) measured vertically from the leading edge of stair treads |
Residential (IRC) vs Commercial (IBC) Stair Code Comparison Matrix
| Stair Dimensional Landmark | Residential Code (IRC R311.7) | Commercial Public Code (IBC 1011) | OSHA Industrial Standard (1910.25) |
|---|---|---|---|
| Maximum Riser Height | 7-3/4 inches (197 mm) | 7.0 inches (178 mm) | 9.5 inches (241 mm) |
| Minimum Riser Height | 4.0 inches (102 mm) | 4.0 inches (102 mm) | — |
| Minimum Tread Run Depth | 10.0 inches (254 mm) | 11.0 inches (279 mm) | 9.5 inches (241 mm) |
| Maximum Step-to-Step Variance | 3/8 inch (9.5 mm) | 3/8 inch (9.5 mm) | 1/4 inch (6.4 mm) |
| Minimum Stairway Clear Width | 36 inches (914 mm) | 44 inches (1118 mm) | 22 inches (559 mm) |
| Minimum Vertical Headroom | 6' 8" (80" / 2032 mm) | 6' 8" (80" / 2032 mm) | 6' 8" (2032 mm) |
| Handrail Height | 34 to 38 inches | 34 to 38 inches | 30 to 38 inches |
| Guardrail Minimum Height | 36 inches (Residential) | 42 inches (Commercial) | 42 inches (OSHA) |
| Guardrail Baluster Spacing | < 4.0" (4-inch sphere rule) | < 4.0" (4-inch sphere rule) | < 4.0" (or intermediate rail) |
The Blondel Formula (Ideal Ergonomic Step Geometry)
Originating from French architect François Blondel in 1675 and validated by modern biomechanics, the natural human walking stride on stairs satisfies the formula:
2 × Riser + 1 × Tread = 24 to 25 inches (60 to 64 cm)
Example: A standard 7.5" riser with a 10" tread ($2 × 7.5 + 10 = 25"$) delivers the most comfortable ascent with minimal quad fatigue and trip hazards.