Mich. Admin. Code R. 408.30519 - [Effective 8/29/2025] Treads and risers

Rule 519. Sections R311.7.5.1 and R 311.7.5.2 of the code are amended to read as follows:

R311.7.5.1. Riser height. The maximum riser height shall be 8-1/4 inches, 210 millimeters. The riser shall be measured vertically between leading edges of the adjacent treads. The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 inch, 9.5 millimeters.

R311.7.5.2. Tread depth. The minimum tread depth shall be 9 inches, 229 millimeters. The tread depth shall be measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread's leading edge. The greatest tread depth within any flight of stairs shall not exceed the smallest by more than 3/8 inch, 9.5 millimeters. Winder treads shall have a minimum tread depth of 10 inches, 254 millimeters, measured as above at a point 12 inches, 305 millimeters, from the side where the treads are narrower. Winder treads shall have a minimum tread depth of 6 inches, 152 millimeters, at any point. Within any flight of stairs, the greatest winder tread depth at the 12-inch, 305 millimeters, walk line shall not exceed the smallest by more than 3/8 inch, 9.5 millimeters.

Notes

Mich. Admin. Code R. 408.30519

2001 AACS; 2004 AACS; 2010 AACS; 2025 MR 10, Eff. 8/29/2025