The nosing on a stair must project no more than how many inches?

The correct projection of the nosing on a stair is critical for safety and usability, ensuring that individuals can safely navigate the steps. In many building codes, including those that apply in Montana, the maximum allowable projection for stair nosing is established as 1 and 1/2 inches. This measurement helps to provide a sufficient edge for users to see and grip as they ascend or descend, which is especially important in varying lighting conditions or for individuals who may have visual impairments.

Having a nosing that exceeds this projection can lead to tripping hazards and complicates the design of the stairs, potentially making them unsafe. The specified limit is a result of comprehensive studies and regulations aimed at maintaining safety standards in construction. Thus, the choice of 1 and 1/2 inches aligns with these safety regulations, making it the correct and most appropriate answer.