Section 1011.1/Stairway Width and Construction
IBC 1011 covers stairway design requirements including minimum width, riser and tread dimensions, headroom, handrails, and construction type for means of egress.
Stairways serving as a means of egress must meet minimum dimensional requirements. Width must be at least 44 inches between handrails for stairways serving an occupant load of 50 or more, or 36 inches for stairways serving fewer than 50 occupants. Risers must be 7 inches maximum and 4 inches minimum. Treads must be 11 inches minimum measured horizontally from nosing to nosing. Riser heights and tread depths must be uniform, with the largest riser or tread within any flight not exceeding the smallest by more than 3/8 inch. Headroom must be at least 6 feet 8 inches measured vertically from the stairway nosing to the ceiling or obstruction above. Handrails are required on both sides per Section 1011.11, and guards are required on open sides more than 30 inches above the floor below per Section 1015.
Why this section exists
Stairways are the primary vertical means of egress during emergencies when elevators are not available. Falls on stairways are one of the leading causes of injury in buildings. The dimensional requirements reflect decades of research into human gait and biomechanics: the 7-inch maximum riser and 11-inch minimum tread produce a comfortable and safe stepping ratio. The uniformity requirement (3/8-inch maximum variation) prevents trips caused by unexpected changes in step geometry. The minimum width ensures adequate capacity for occupant egress flow, calculated per Section 1005.1.
What plan reviewers look for
Plan reviewers check stairway sections and plans for riser height, tread depth, width, headroom, and handrail compliance. They verify that the stairway width meets the required egress width based on occupant load calculations. They check that exit stairways are enclosed with the required fire- resistance rating (1 hour for buildings 4 stories or less, 2 hours for buildings more than 4 stories). They verify handrails on both sides, proper guard heights, and that landings are provided at doors and at intervals not exceeding 12 feet of vertical rise.