1. (1) Employers must meet the following requirements for spiral stairways:

   1. (a) Stairways must conform to the minimum dimensions of Figure F-1;

      Figure F-1

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      Spiral Stairway—Minimum Dimensions
      	A (Half-tread width)	B
      Normal use byemployees . . . .	11 inches(27.9 cm)	6 inches(15.2 cm)
      Limited access . . . .	9 inches(22.9 cm)	5 inches(12.7 cm)

   2. (b) Stairway risers must be uniform and range from six and one-half to 10.5 inches (16.5 to 26.67 cm) in height;
   3. (c) Minimum loading capability be 100 pounds per square foot (445 N), and minimum tread center concentrated loading shall be 300 pounds (1334 N);
   4. (d) Railing must conform to the requirements of WAC 296-56-60123(3). If balusters are used, there must be a minimum of one per tread. Handrails must be a minimum of one and one-fourth inches (3.18 cm) in outside diameter; and
   5. (e) Vertical clearance must be at least six feet, six inches (1.98 m) above the top step.
2. (2) Employers must maintain spiral stairways in safe condition.

[Statutory Authority: RCW 49.17.010, 49.17.040, 49.17.050, 49.17.060, 70.54.480, and chapter 49.17 RCW. WSR 26-07-053, s 296-56-60217, filed 3/17/26, effective 4/20/26. Statutory Authority: RCW 49.17.010, 49.17.040, 49.17.050, 49.17.060. WSR 15-24-102, § 296-56-60217, filed 12/1/15, effective 1/5/16. Statutory Authority: RCW 49.17.010, [49.17].040, and [49.17].050. WSR 00-21-103, § 296-56-60217, filed 10/18/00, effective 2/1/01. Statutory Authority: RCW 49.17.040. WSR 99-02-024, § 296-56-60217, filed 12/30/98, effective 3/30/99. Statutory Authority: RCW 49.17.040 and 49.17.050. WSR 86-03-064 (Order 86-02), § 296-56-60217, filed 1/17/86; WSR 85-10-004 (Order 85-09), § 296-56-60217, filed 4/19/85; WSR 85-01-022 (Order 84-24), § 296-56-60217, filed 12/11/84.]