Section 1011 — STAIRWAYS

1011.5.5 Modify the first sentence of the first paragraph as follows:

For all occupancies except R-3 one and two family dwellings and townhouses nosings shall have a curvature or bevel of not less than 1/16 [1 ] (1.6 mm) but not more than 9/16 [1 ] (14.3 mm) from the foremost projection of the tread. Risers shall be solid and vertical or sloped under the tread above from the underside of the nosing above at an angle not more than 30 degrees (0.52 rad) from the vertical.

1011.5.5 Add a second paragraph as follows:

For R-3 one- and two-family dwellings and townhouses, the radius of curvature at the nosing shall be no greater than 9/16 inch (14 mm). A nosing not less than 3/4 inch (19 mm) but not more than 1-1/4 inches (32 mm) shall be provided on stairways with solid risers. The greatest nosing projection shall not exceed the smallest nosing projection by more than 3/8 inch (9.5 mm) between two stories, including the nosing at the level of floors and landings. Beveling of nosings shall not exceed 1/2 inch (12.7 mm).

Exception: A nosing projection is not required where the tread depth is not less than 11 inches (279 mm). [ CRC R311.7.5.3 ]

1011.5.5.1 Modify the first sentence of the first paragraph as follows:

For all occupancies except R-3 one- and two-family dwellings and townhouses the leading edge (nosings) of treads shall project not more than 1¼ inches (32 mm) beyond the tread below.