Treads, landings and floors of stairways shall have a radius of curvature at the nosing not greater than 9/16 inch (14 mm) PHOTO 21 or a bevel not greater than ½ inch (12.7 mm) PHOTO 22. A nosing projection not less than ¾ inch (19 mm) and not more than 1¼ inches (32 mm) shall be provided on stairways PHOTO 23. The greatest nosing projection shall not exceed the smallest nosing projection by more than ⅜ inch (9.5 mm) within a flight of stairs and the landings at the top of the flight. PHOTO 24.
Exceptions: 1. A nosing projection is not required where the tread depth is not less than 11 inches (279 mm).
- Where risers are open, the maximum nosing projection shall be permitted to exceed 1¼ inches (32 mm).
