What is the minimum effective platform width where doors open directly onto a stairway?

The minimum effective platform width where doors open directly onto a stairway is 20 inches. This requirement is established to ensure safe access and egress. The rationale behind this specification is to provide adequate space for individuals to enter or exit through the door without risking a fall or obstruction when the door swings open.

If the platform were narrower than this minimum width, it could lead to hazardous situations where a person might not have enough room to maneuver safely as they enter or exit, especially if they are carrying items or if there's a risk of the door inadvertently striking someone. Maintaining a minimum effective platform width helps to protect individuals from accidents in these critical transition areas, emphasizing safety in design.