Stair code requirements
| What | The rule | IRC 2024 / 2021 |
|---|---|---|
| Riser height | 7 3/4 in (196 mm) at most, measured between the leading edges of the treads. | R318.7.5.1 / R311.7.5.1 |
| Tread depth | 10 in (254 mm) at least, nosing to nosing. | R318.7.5.2 / R311.7.5.2 |
| Same size all the way | The largest riser may exceed the smallest by 3/8 in (9.5 mm) at most in one flight; the same for treads. | R318.7.5.1–.2 / R311.7.5.1–.2 |
| Nosing | 3/4 to 1 1/4 in (19–32 mm) on solid risers; not required where treads are 11 in (279 mm) or deeper. | R318.7.5.3 / R311.7.5.3 |
| Open risers | Where the opening is more than 30 in (762 mm) above the floor or grade below, a 4 in (102 mm) ball must not pass through. | R318.7.5.1 / R311.7.5.1 |
| Headroom | 6 ft 8 in (2032 mm) at least, measured straight up from the line of the nosings. | R318.7.2 / R311.7.2 |
| Rise of one flight | 12 ft 7 in (3835 mm) at most between floors or landings; a taller stair needs a landing. | R318.7.3 / R311.7.3 |
| Width | 36 in (914 mm) clear above the handrail; 31 1/2 in (787 mm) at and below it with one handrail, 27 in (698 mm) with two. | R318.7.1 / R311.7.1 |
| Landings | A floor or landing at the top and bottom of each flight, at least as wide as the stair and 36 in (914 mm) deep on a straight run. | R318.7.6 / R311.7.6 |
| Handrail | On at least one side of every flight with four or more risers, 34 to 38 in (864–965 mm) above the nosings. | R318.7.8, R320.2 / R311.7.8 |
| Guard | On open sides more than 30 in (762 mm) above the floor or grade; at least 34 in high along a stair, measured from the nosings. | R321.1 / R312.1 |