Passenger loading zones shall have an adjacent access aisle complying with Section 503.3.
A vertical clearance of 114 inches (2895 mm) minimum shall be provided at the following locations:
All steps on a flight of stairs shall have uniform riser height and uniform tread depth. Risers shall be 4 inches (100 mm) minimum and 7 inches (180 mm) maximum in height. Treads shall be 11 inches (280 mm) minimum in depth.
The radius of curvature at the leading edge of the tread shall be 1/2 inch (13 mm) maximum. Nosings that project beyond risers shall have the underside of the leading edge curved or beveled. Risers shall be permitted to slope under the tread at an angle of 30 degrees maximum from vertical. The permitted projection of the nosing shall be 11/2 inches (38 mm) maximum over the tread or floor below.
Handrails shall be continuous within the full length of each stair flight or ramp run. Inside handrails on switchback or dogleg stairs or ramps shall be continuous between flights or runs. Other handrails shall comply with Sections 505.10 and 307.
EXCEPTION: Handrails shall not be required to be continuous in aisles serving seating where handrails are discontinuous to provide access to seating and to permit crossovers within the aisles.
Clearance between handrail gripping surface and adjacent surfaces shall be 11/2 inches (38 mm) minimum.
Gripping surfaces shall be continuous, without interruption by newel posts, other construction elements, or obstructions.
- Not more than 20 percent of the handrail length is obstructed,
- Horizontal projections beyond the sides of the handrail occur 11/2 inches (38 mm) minimum below the bottom of the handrail, and provided that for each 1/2 inch (13 mm) of additional handrail perimeter dimension above 4 inches (100 mm), the vertical clearance dimension of 11/2 inch (38 mm) can be reduced by 1/8 inch (3.2 mm), and
- Edges shall be rounded.
Handrails shall extend beyond and in the same direction of stair flights and ramp runs in accordance with Section 505.10.
At the top of a stair flight, handrails shall extend horizontally above the landing for 12 inches (305 mm) minimum beginning directly above the landing nosing. Extensions shall return to a wall, guard, or the landing surface, or shall be continuous to the handrail of an adjacent stair flight.
At the bottom of a stair flight, handrails shall extend at the slope of the stair flight for a horizontal distance equal to one tread depth beyond the bottom tread nosing. Extensions shall return to a wall, guard, or the landing surface, or shall be continuous to the handrail of an adjacent stair flight.