R311.7.8.3

Section R311.7.8.3 is titled 'Handrail clearance' and covers the requirements for providing a minimum amount of space between handrails and adjacent elements, such as walls, barriers, or other protrusions, such as treads on switchback stairs. (Even though the section only specifically says 'walls', other elements are intended as well.) The purpose of this section is to provide adequate space for fingers to grasp a handrail, in order to reduce trip and fall hazards.

The model shows a partial stairway with a handrail and the required clearance dimension highlighted. Notice the handrail must adjust for the protruding tread from the adjacent switchback flight, in order to be fully compliant with this section.