Associates working within pick modules or on rack supported platforms to retrieve items stored above the facility floor access those higher levels via stairways. Protecting those workers from falls is, therefore, of critical importance. For that reason, the safe design of stairs is included in RMI’s ANSI MH16.1-2012: Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks, as sub-section 8.4.4 within the “Pick Modules and Rack Supported Platforms” guidelines.
Additionally, RMI partnered with the Storage Manufacturers Association (SMA) to develop ANSI MH32.1-2018: Stairs, Ladders, and Open-Edge Guards for Use with Material Handling Structures, a standard whose provisions specifically apply to fixed stairways attached to structures, such as industrial racking pick modules; decked-over platforms; industrial shelving pick modules and decked-over platforms; and free-standing work platforms.
The sections pertaining to stairs in both documents apply solely to stairs used by trained personnel—as opposed to those used by the public. However, it is important to note that many municipalities have (and enforce) specific requirements for stairs that may be more stringent than those called for in the RMI and RMI/SMA standards.
The RMI and RMI/SMA standards detail a variety of requirements intended to keep operators safe while traversing the stairs, such as:
- Pitch: Stairway slope angles can range from 30° to 50°.
- Headroom: Vertical clearance from the tip of the tread nose or the pitch line should be 80 inches at a minimum.
- Height: Single stairways without landings can be no taller than 20 feet in height.
- Tread Rise: Each step can be no taller than 9 inches as measured from the top of one tread to the next adjacent tread, and all steps must have the same rise.
- Tread Projection: Each tread must be at least 7.5 inches deep, and all treads must project the same distance.
- Surface: Each step’s surface can be solid or perforated with openings no larger than 1.125 inches.
- Loading: Each stair must be able to withstand a concentrated point load of 300 pounds.
- Guarding: The open side of any stairway rising higher than 30 inches must be guarded at a minimum height of 42 inches and designed to prevent a 21-inch-diameter sphere from passing through any opening.
- Handrails: Stair handrails are required on stairways with a total rise greater than 44 inches and must measure between 30 inches and 34 inches in height from the top of each tread. Handrails can also serve as the top of guarding, as long as their position is between 34 inches and 38 inches from the tread surface and that they are built to prevent a 21-inch-diameter sphere from passing through any opening.
Looking for more details about safe stair design for elevated work platforms? Download a free copy of the RMI/SMA ANSI MH32.1-2018: Stairs, Ladders, and Open-Edge Guards for Use with Material Handling Structures specification, here.