Guard Definition and Requirements
Guards are in place to prevent accidental falls. They are generally not required unless there is a 30″ drop – which may vary by local Authority Having Jurisdiction (AHJ).
In residential applications, the guard height minimum is 36″. On a stair, since handrail must be between 34″ and 38″, the handrail and the top of the guard can be one and the same.
In commercial applications, the IBC requires a minimum height of 42″. On stairs, once there is a 30″ drop, both a handrail and a guard will be required with the guard at a minimum height of 42″ and the handrail placed between 34″ and 38″ above the nosing.
4″ sphere rule – no opening large enough to pass a 4″ sphere is permitted.