Michigan Compiled Laws, Chapter 252. Highways § 252.315

(a) In counties of less than 425,000 population, signs shall not exceed 1,200 square feet in area, including border or trim but excluding ornamental base or apron, supports and other structural members.

(b) In counties having a population of 425,000 or more, signs of a size exceeding 1,200 square feet in area but not in excess of 6,500 square feet in area, including border or trim but excluding ornamental base or apron, supports and other structural members, shall be permitted if the department determines that the signs are in accord with customary usage in the area where the sign is located.

(c) For signs erected after March 23, 1999, signs on a sign structure shall not be stacked 1 on top of another. For signs erected prior to March 23, 1999, the sign or sign structure shall not be modified to provide a sign or sign structure that is stacked 1 on top of another.

(a) The sign being divided is not a nonconforming sign.

(b) The resulting smaller sign faces are equal in size.

(c) Each of the resulting smaller sign faces does not exceed 350 square feet in area.

(d) Each of the resulting smaller sign faces is legally permitted under this act.

(e) Both before and after the larger sign face is divided into smaller sign faces, there are no more than 2 permits for signs at that location facing the same direction of travel.