What should be the maximum diameter of a sphere to pass through the triangular area formed by a tread, riser, and guard?

The maximum diameter of a sphere that can pass through the triangular area formed by a tread, riser, and guard is relevant for ensuring safety and compliance with building codes, particularly in relation to stair design and child safety.

In stair design, the triangular area created between the tread, riser, and guard provides a crucial space that must not allow objects larger than a specific diameter to pass through, as this could pose a risk of entrapment for young children. The maximum diameter of 6 inches for the sphere is considered a standard safety measure derived from various building codes and safety guidelines. This size is intended to ensure that a child's head cannot pass through the openings, thereby reducing the risk of a child getting stuck or injured.

Knowing the standard maximum diameter helps inspectors assess stair safety features effectively. The choice of 6 inches reflects established practices in construction and safety design, ensuring that the dimensions accommodate both functionality and safety within residential structures.