Ships ladders, ship stairs, ship ladder stairs, alternating tread stairs, fixed ladders are all terms that can get confused and sometimes used interchangeably. How do these devices differ from each other? Let's look at how OSHA defines stairways, alternating tread stairs, ship stairs, ship ladders, and fixed ladders to understand the difference.
Stairway (stairs) means risers and treads that connect one level with another, and includes any landings and platforms in between those levels. Stairways include standard, spiral, alternating tread-type, and ship stairs.
Ship stair (ship ladder) means a stairway that is equipped with treads, stair rails, and open risers, and has a slope that is between 50 and 70 degrees from the horizontal.
Fixed ladder means a ladder with rails or individual rungs that is permanently attached to a structure, building, or equipment. Fixed ladders include individual-rung ladders, but not ship stairs, step bolts, or manhole steps.
OSHA Stair and Ladder Design Standards
OSHA defines ship stair and ship ladder interchangeably so it is understandable that many people use these terms to mean the same thing. Looking at the design standards also helps to differentiate the different types of devices, starting with the angles of the devices.
30° - 50°
50° - 70°
Alternating Tread-Type Stairs
60° - 90°
OSHA Stair angle can be up to 50 degrees, ship stair and alternating tread stair angle up to 70 degrees and ladder angle up to 90 degrees. Between 60 degrees and 70 degrees the angles of ship stairs or ship ladders and ladders overlap, so using the angle of the device is not necessarily a great way to differentiate.
Another important design requirement for ship stairs is found in OSHA 1910.28:
1910.28(b)(11)(iii) Each ship stairs and alternating tread type stairs is equipped with handrails on both sides.
The handrail on either side of the ship stair or alternating tread stair acts as the fall protection similarly to a stair rail system. Fixed Ladders do not have an integrated railing for fall protection.
OSHA Ladder Use
A more general difference between a stair and a ladder is the way in which they are used. OSHA 1910.23 states the following requirements on employees using ladders.
1910.23(b)(11) Each employee faces the ladder when climbing up or down it;
1910.23(b)(12) Each employee uses at least one hand to grasp the ladder when climbing up and down it; and
1910.23(b)(13) No employee carries any object or load that could cause the employee to lose balance and fall while climbing up or down the ladder.
Stairways, ship stairs, and alternating tread stairs are not subject to these requirements. Stairways and alternating tread stairs can both be descended face forward in the direction of travel. Some ship stairs can be descended face forward depending on how steep the angle. We saw earlier that between 50-60 degrees, the angles of ship stairs and ladders overlap. Generally, ship stairs shallower than 60 degrees may be designed as face-forward descent devices. Anything steeper than that should be backed down facing the device like a ladder. In that case, employees should follow the same rules for descending ship ladders as for descending fixed ladders. So one way to think of the difference between a ship stair and a ship ladder is that a ship stair can be face-forward descent while a ship ladder is backed-down descent. Often we hear the term "ship ladder stair" to refer to the face-forward type of ship stair.