What is the minimum clear tread depth for a spiral stairway at a point 12 inches from the narrow edge?

The minimum clear tread depth for a spiral stairway at a point 12 inches from the narrow edge is established by building codes to ensure safety and usability. For spiral staircases, the tread depth differs from standard straight staircases due to their unique design.

A tread that is at least 7-1/2 inches deep at this distance helps to provide adequate space for foot placement, reducing the risk of slips and falls. This measurement is critical in creating a comfortable and safe walking surface, especially in commercial settings where the stairs might experience heavier foot traffic.

Choosing a tread depth that is less than 7-1/2 inches might not provide enough space for users to comfortably place their feet, which could lead to accidents. Conversely, a tread depth greater than this measurement is not specified as the minimum requirement for the particular situation described in the code, focusing on maintaining both structural integrity and safety within the design parameters set forth for spiral stairways.