29 CFR § 1917.121 - Spiral stairways.

---
identifier: "/us/cfr/t29/s1917.121"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "29 CFR § 1917.121 - Spiral stairways."
title_number: 29
title_name: "Labor"
section_number: "1917.121"
section_name: "Spiral stairways."
chapter_name: "OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR"
part_number: "1917"
part_name: "MARINE TERMINALS"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "33 U.S.C. 941; 29 U.S.C. 653, 655, 657; Secretary of Labor's Order No. 12-71 (36 FR 8754), 8-76 (41 FR 25059), 9-83 (48 FR 35736), 1-90 (55 FR 9033), 6-96 (62 FR 111), 3-2000 (65 FR 50017), 5-2002 (67 FR 65008), 5-2007 (72 FR 31160), 4-2010 (75 FR 55355), 1-2012 (77 FR 3912), or 8-2020 (85 FR 58393), as applicable; and 29 CFR part 1911."
regulatory_source: "48 FR 30909, July 5, 1983, unless otherwise noted."
cfr_part: "1917"
---


# 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

|  | 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.

(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]