Section R. 400.11209 - Interior finishesRule 209.
(1) In new construction, additions, conversions, renovations, or remodeling, interior finish classification shall be of the basic material used without regard to subsequently applied paint or other covering in an attempt to meet the classification. The basic material shall be a minimum of class B in a means of egress and a minimum of class C in other areas. All of the following provisions also apply to new construction, additions, conversions, renovations, and remodeling:(a) In a portion of a building not used by campers, the interior finish may be less than required by these rules if a 1-hour fire separation exists between the camper-occupied area and the non-camper-occupied area. Any door openings in the 1-hour separation shall be protected with B labeled fire door and frame assemblies.(b) Interior finish material that is more hazardous than class C material is not permitted.(c) Interior finish materials in basements occupied by campers shall be a minimum of class B throughout.(d) Prefinished plywood or paneling of minimum 1/4 inch thickness with proven class A, B, or C interior finish classification may be applied to studs. Prefinished plywood or paneling less than 1/4 inch thick with a proven A, B or C interior finish classification shall be installed on a noncombustible backer. Standard lath and plaster or drywall is acceptable as an interior finish anywhere.(2) Existing licensed organizations with buildings having existing interior finishes that do not comply with those specified in subrule (1) of this rule may have those finishes coated in accordance with the following conditions:(a) The unapproved finish is applied directly to a noncombustible backing.(b) The unapproved finish is not furred out more than 1-inch from the noncombustible backing.(c) An approved fire-retardant coating is used, which has been tested for use on the applicable finish, meets the required interior finish rating, and is applied in accordance with its listing.Mich. Admin. Code R. 400.11209