Section R. 400.18645 - Inside stairwaysRule 645.
(1) An inside stairway that forms an approved means of egress shall have suitable handrails on each side.(2) An inside stairway that forms an approved means of egress shall be not less than 36 inches wide in the clear. Handrails attached to walls may project not more than 3 1/2 inches at each side into the required width of a stairway.(3) A stairway that forms an approved means of egress shall have treads that are not less than 8 inches wide, exclusive of the nosing, and risers that are not more than 8 1/2 inches in height. Treads and risers shall be of uniform width and height in each individual stairway.(4) An inside stairway which forms a means of egress which consists of 2 or more steps, and which, in changing direction, does so by benefit of the variance in the width along each tread shall not be approved. This rule does not prohibit a stairway with treads of uniform width throughout that changes directions by benefit of intermediate landings or platforms.Mich. Admin. Code R. 400.18645