What is the maximum riser height for stairs leading to an open sun-deck located above a carport for a single family residence in the City of Los Angeles?
According to the Los Angeles Code SEC. 57.1009. STAIRWAYS — Section 1009 of the CFC is adopted in its entirety, stated below.
2013 CALIFORNIA FIRE CODE
1009.7.2 Riser height and tread depth. Stair riser heights shall be 7 inches (178 mm) maximum and 4 inches (102 mm) minimum. The riser height shall be measured vertically between the nosings of adjacent treads. Rectangular tread depths shall be 11 inches (279 mm) minimum measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread’s nosing. Winder treads shall have a minimum tread depth of 11 inches (279 mm) between the vertical planes of the foremost projection of adjacent treads at the intersections with the walkline and a minimum tread depth of 10 inches (254 mm) within the clear width of the stair.
Exceptions:
1. Alternating tread devices in accordance with Section 1009.13.
2. Ship ladders in accordance with Section 1009.14.
3. Spiral stairways in accordance with Section 1009.12.
4. Aisle stairs in assembly seating areas where the stair pitch or slope is set, for sightline reasons, by the slope of the adjacent seating area in accordance with Section 1028.11.2.
5. In Group R-3 occupancies; within dwelling units in Group R-2 occupancies; and in Group U occupancies that are accessory to a Group R-3 occupancy or accessory to individual dwelling units in Group R-2 occupancies; the maximum riser height shall be 7 3 /4 inches (197 mm); the minimum tread depth shall be 10 inches (254 mm); the minimum winder tread depth at the walkline shall be 10 inches (254 mm); and the minimum winder tread depth shall be 6 inches (152 mm). A nosing projection not less than 3 /4 inch (19.1 mm) but not more than 11 /4 inches (32 mm) shall be provided on stairways with solid risers where the tread depth is less than 11 inches (279 mm).
6. See Section 3404.1 of the California Building Code for the replacement of existing stairways.
7. In Group I-3 facilities, stairways providing access to guard towers, observation stations and control rooms, not more than 250 square feet (23 m2 ) in area, shall be permitted to have a maximum riser height of 8 inches (203 mm) and a minimum tread depth of 9 inches (229 mm).
8. [SFM] Stairways providing access to lifeguard towers not open to the public, not more than 250 square feet (23 m2 ) in area, shall be permitted to have a maximum riser height of 8 inches (203 mm) and a minimum tread depth of 9 inches (229 mm).
While the CFC states a 7" max riser, the City of LA Department of Buildings Single Family Dwelling / Duplex Plan Checklist references an exception for a 8” riser & 9” run (code section 91.1003.3.3.3). These values coincide with the County of Los Angeles Building Code, Chapter 10, Section 1003.3.3.3, which states the following:
The rise of steps and stairs shall not be less than 4 inches nor more than 7 inches. The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8&.the run shall not be less than 11 inches as measured horizontally between the vertical planes of the furthermost projection of adjacent treads or nosings. Stair treads shall be of uniform size and shape, except the largest tread run within any flight of stairs shall not exceed the smallest by more than 3/8 inch. Exceptions for private steps and stairways serving an occupant load of less than 10 and stairways to unoccupied roofs may have a maximum rise of 8 inches and a minimum run of 9 inches. Finally, risers adjacent to a public way, walkways or a driveway serving as a landing can have risers less than 4 inches in height with restrictions on the variation in height from the top and bottom risers.
