CFR

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;

Code of Federal Regulations

[Please see PDF for image: EC21OC91.020 ]

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 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.

Code of Federal Regulations

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

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