What is the maximum projection of the leading edge (nosing) of treads beyond the tread below?

The maximum projection of the leading edge of treads beyond the tread below is established to ensure both safety and usability of staircases. A projection of 1-1/4 inches is appropriate because it allows for effective use of the stairs while minimizing the risk of tripping. This dimension strikes a balance between providing enough surface area for foot placement and limiting the risk of overhang that could interfere with the stair user’s ability to navigate the stairs safely.

In building codes and standards, such as the International Building Code (IBC), specific measurements are often designated to enhance accessibility and safety. The maximum projection is set as 1-1/4 inches to accommodate a range of foot sizes and to maintain a clear pathway. Larger projections could pose hazards by pushing users too far into the next step or leading to missteps.

This choice reflects standard industry practices and aligns with the principles of both safety and accessibility outlined in building regulations.