Q: I’m building a house with a loft accessed by a code-approved stair. The client also wants a ship’s ladder to the loft for the kids. Does code allow unorthodox stairs if a legal one is in place to access the same area?

A: Glenn Mathewson, a building official in Westminster, Colo., replies: Unorthodox stair designs, such as ship’s ladder stairs, aren’t specifically addressed by the IRC. So acceptance would be up to the individual authority—and some authorities may trump any kind of justification with a simple “not in my town” response. But let’s see how I might approach approving this secondary means of ascent.

The IRC regulates “stairs” and defines them as a change in elevation from one level to the next, and it generally follows a philosophy of “if you build it, they will come”—meaning no matter how many stairs you provide, people will use them all and they must all provide the safety we have come to expect. This means that if you build a stairway and it looks and feels like a stairway, folks will use that stairway. If a home has two stairways to the second floor, both must comply, as both have equal opportunity to be used. Both are considered “means of egress.”

However, the IRC does provide for some variety in stairways, such as for winder treads or spiral stairs. The geometry on spiral stairs is more forgiving than standard stairs, but the stair user is also well aware that they are not on normal stairs; thus, their attention is heightened to the stair’s more claustrophobic design. That would be my philosophical approach to a ship’s ladder stair—you know when you’re on a ladder, and you won’t expect it to work like a stairway.

To the potential user of a ship’s ladder stair to a loft, it’s clear that extra consideration needs to be taken that is quite different from the innocent choice to use one stairway rather than another only to find it’s not what you expected. There is always some occupant responsibility to be assumed.

While the IRC doesn’t regulate ship’s ladder stairs, the IBC does for commercial applications (IBC 2012 1009.14). Minimum tread depth is 5 inches, with each tread extending out at least 3 1/2 inches from the step above. The maximum riser height is 9 1/2 inches, with handrails required on each side. As a reality check, this ladder is safer and less steep than the maximum ladder slope permitted by OSHA (1 foot in 4 feet), and certainly not as steep as the bunk bed ladder your little superhero climbs up every night.

No matter what kind of ladder is installed, there’s still a very real fall hazard at the top of the ladder. But perhaps an in-swinging gate in the railing at the top of the ladder would take care of that issue.