Final answer:
Typically, main stairways in residential settings will have at least two stringers, one on each side, with wider stairways requiring an additional middle stringer. In commercial buildings, the number of stringers is dictated by local building codes for safety and stability.
Step-by-step explanation:
The number of stringers used on main stairways can vary, but typically, a main residential stairway will have at least two stringers; one on each side. However, for wider stairways, an additional stringer may be added in the middle to provide extra support.
This is particularly true for stairways that are wider than 36 inches, as additional support is necessary to ensure the stability of the steps and the overall integrity of the stair structure.
In commercial or public buildings, the building codes will dictate the number of stringers required for safety and stability. Local building codes must always be consulted when constructing stairways to ensure compliance with all safety regulations and requirements.
Moreover, for exceptionally wide stairs, more than three stringers may be used. The decision on how many stringers to use will take into account factors such as the width of the stairs, expected load, the material of the steps, and safety considerations.