(a) Definition. "Spiral stairway" means one with closed circular form, uniform sector-shaped treads and a supporting column.

(b) Requirements. Spiral stairways shall meet the following requirements:   (1) Stairways shall conform to the minimum dimensions of Figure F-1; Spiral Stairway — Minimum Dimensions A (half-tread width) B Normal use by employees 11 inches (27.94 cm) 6 inches (15.24 cm). Limited access 9 inches (22.86 cm) 5 inches (12.7 cm).   (2) Stairway risers shall be uniform and shall range from 6½ to 10½ inches (16.5 to 26.67 cm) in height;   (3) Minimum loading capability shall be 100 pounds per square foot (4.79kN), and minimum tread center concentrated loading shall be 300 pounds (1334 N);   (4) Railings shall conform to the requirements of §1917.112(c)(1). If balusters are used, there shall be a minimum of one per tread. Handrails shall be a minimum of 1¼ inches (3.18 cm) in outside diameter; and   (5) Vertical clearance shall be at least 6 feet, 6 inches (1.98 m) above the top step.

(c) Maintenance. Spiral stairways shall be maintained in safe condition.

[48 FR 30909, July 5, 1983, as amended at 62 FR 40201, July 25, 1997; 65 FR 40942, June 30, 2000]