A third stairway stringer is recommended when the stair width exceeds how many inches?

A third stairway stringer is recommended when the stair width exceeds how many inches?

• A. 30 inches
• B. 28 inches
• C. 32 inches
• D. 34 inches

Answer: (A)

In stair construction, the number of stringers depends on how wide the stairway is. As width increases, the load on the two outer stringers and the middle portion of the treads increases, which can lead to more deflection, bounce, and less stable handrail anchorage. Introducing a third stringer adds a central support, distributing the weight more evenly and keeping the treads flatter and the railing aligned. Choosing 30 inches as the threshold means that once the stair width exceeds 30 inches, the added support of a third stringer helps maintain strength and safety across the wider span. Narrower stairs can usually be adequately supported by two stringers, while wider stairs benefit from the extra center support. So, when the stair width goes beyond 30 inches, a third stringer is recommended to improve stability, reduce deflection, and ensure safer, more comfortable use.

In stair construction, the number of stringers depends on how wide the stairway is. As width increases, the load on the two outer stringers and the middle portion of the treads increases, which can lead to more deflection, bounce, and less stable handrail anchorage. Introducing a third stringer adds a central support, distributing the weight more evenly and keeping the treads flatter and the railing aligned.

Choosing 30 inches as the threshold means that once the stair width exceeds 30 inches, the added support of a third stringer helps maintain strength and safety across the wider span. Narrower stairs can usually be adequately supported by two stringers, while wider stairs benefit from the extra center support.

So, when the stair width goes beyond 30 inches, a third stringer is recommended to improve stability, reduce deflection, and ensure safer, more comfortable use.