minimum stair tread width
Stairways shall be maintained clear and in good repair. (Title 24, Part 2, Section 2-3305(s).). (e) Circular Stairways. Circular stairs may be used as an exit providing the minimum width of run is not less than 10 inches and the smaller radius is not less than twice the width of the stairway. All treads in any one flight between landings shall have identical dimensions within a three-eighths inch tolerance.