§ 1917.121 — Spiral Stairways

(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

(2) Stairway risers shall be uniform and shall range from 6

1/2 to 10

1/2 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 1

1/4 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.