(a) Class II systems shall be located in buildings having walls of masonry or noncombustible construction and wall finish shall be plain or plastered without furring or concealed spaces. Floors shall be of fire-resistive construction and without pits, wells or pockets; and where located over a basement, floor shall be vapor- and liquid-tight. Roof and floors above grade floor, if of combustible construction, shall have the ceilings over the dry cleaning areas protected by cement or gypsum plaster on metal lath or equivalent construction. Dry cleaning buildings shall not be closer than 10 feet to the line of adjoining property, except that if exposing walls are equivalent to 12-inch brick construction without openings the building may be located on the property line.
(b) Dry cleaning operations shall be restricted to the first floor above grade and shall not be located on any floor below grade nor in the same building with other occupancies. Operations incidental to the dry cleaning business such as laundering, pressing, and ironing, may be in a communicating building or located on the same floor with the dry cleaning plant, provided the dry cleaning operations are separated therefrom by partitions having a fire-resistance rating of not less than two hours and communicating openings are protected by fire doors approved for such openings.
(c) Door openings on stairs or elevators leading from a dry cleaning area to a basement, or opening into a room having openings or stairs to basements, shall be provided with noncombustible sills or ramps raised at least 6 inches. Approved self-closing fire doors shall be provided at such openings. Enclosures shall be of construction equivalent to the floor construction but having a fire-resistance rating of not less than one hour.