Mich. Comp. Laws § 125.467: Water closet accommodations.

Sec. 67.

Water-closet accommodations. In every dwelling existing prior to the passage of this act there shall be provided at least 1 water-closet for every 2 apartments, groups or suites of rooms, or fraction thereof, except that in multiple-dwellings of class B there shall be provided at least 1 water-closet for every 15 occupants or fraction thereof.