1917.121—Spiral stairways.
(a) Definition.
“Spiral stairway” means one with closed circular form, uniform sector-shaped treads and a supporting column.
Code of Federal Regulations
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