Staircase Width and Staircase Reinforcement Detailing
Staircase width refers to the side to side distance of the staircase when you are walking down or up the stairs. This minimum distance must be 0.9 M or 36 inches or more for residential houses or one-way traffic and 1.50 M or 50 feet for two-way traffic. This minimum measurements does not include handrails. Staircase width that is too narrow is a hazard in many ways.
Check the video below for staircase reinforcement details