In buildings four or more stories or more than 40 feet (12 192 mm) in height above grade, one stairway shall extend to the roof surface through a stairway bulkhead complying with Section 1509.2, unless the roof has a slope steeper than 20 degrees (0.35 rad). Access to setback roof areas may be through a door or window opening to the roof. Stairs terminating at the level of a setback shall provide access to the setback roof areas, except where the setback is less than 4 feet (1219 mm) in width and 10 feet (3048 mm) in length, measured from the inside of the parapet wall.
In buildings in Occupancy Groups I-1, R- 1 and R-2 two stories or more in height, with roofs having a slope of 15 degrees (0.26 rad) or less, all interior stairs, except those terminating at the level of a setback roof, shall extend to the roof surface.
- In buildings in Occupancy Groups R- 1 and R-2 two stories in height and in Occupancy Group R-2 three stories in height with not more than one dwelling unit per story, access to the roof shall be permitted to be a noncombustible roof hatch or trap door not less than 21 inches (533 mm) in width and 28 inches (711 mm) in length. Such hatches shall be located within the stair enclosure and be provided with a stationary, noncombustible access ladder or alternating tread device.
- In buildings in Occupancy Group R-2 complying with Item 4 of Section 1021.2, roof access shall be governed by Item 4.6 of such section.