Standard Stair Width and Other Important Measurements
By Stefan Gheorghe
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The standard stair width for residential stairs in the U.S. is 36 inches minimum, according to building codes. Many homeowners choose widths between 36 and 42 inches for comfort. Wider stairs, up to 48 inches, are also common in modern homes to allow easier passage and moving of large items.
| Measurement | Standard / Code Requirement |
|---|---|
| Stair width | 36 inches minimum; 36–42 inches typical |
| Tread depth (run) | Minimum 10 inches |
| Riser height | Maximum 7 3/4 inches |
| Tread thickness | 1 to 1 1/4 inches |
| Headroom | Minimum 6 feet 8 inches |
| Landing width | Equal to stair width; minimum 36 inches |
| Open riser spacing | Less than 4 inches |
| Nosing projection | 3/4 inch to 1 1/4 inches |
Spiral Staircases
For spiral staircases, the IRC recommends a minimum diameter of 5 feet. Each tread should provide a walking width of at least 36 inches.
Railing Guidelines
- Railing height: 34–38 inches
- Spindle spacing: No more than 4 inches apart
- 27-inch rule: If handrails are on both sides, there must be at least 27 inches of clear width between them.