Fire-retardant ceilings shall be constructed in accordance with one of the following specifications:
(a) No less than three-quarter inch plaster on expanded metal lath securely attached to steel supports by wire or special metal fasteners, not over six inches on center, or, in buildings whose types of construction permit wood framing, attached to wood supports by not smaller than one and one-half inches eleven gauge, seven-sixteenths inch head-barbed roofing nails not over six inches on center, or by equivalent staples. Plaster shall consist of one part gypsum to not over two parts sand for the scratch coat and one part gypsum to not over three parts sand for the brown coat, or shall consist of Portland cement and sand in the same proportions, except that three pounds of asbestos fiber shall be added with each bag of cement.
(b) In buildings whose types of construction permit wood framing, not less than one-half inch plaster, consisting of one part gypsum to not over two parts sand, on three-eighths inch perforated gypsum lath with one perforation of not less than three-fourths inch diameter for not more than sixteen square inches of lath surface, attached to wood supports by nails not smaller than one and one-eighth inches long with three-eighths inch diameter heads, spaced not more than four inches on center. Three-inch wide strips of expanded metal lath shall be nailed over all joints in the gypsum lath with nails not smaller than one and three-fourths inches long with one-half inch heads.
(c) Any combination floor and ceiling construction having a fire-resistance rating of one hour or more.
(Ord. 42-1981. Passed 2-23-81.)