A. Ratproofing consists of the closing and keeping closed of all openings in the exterior walls, ground or first floors, basements, roofs, sidewalk gratings, sidewalk openings, foundations, elevator shafts, fire escapes, and other places that may be reached and entered by rats by climbing, burrowing or otherwise.
B. The material to be used for ratproofing shall include cement, concrete, brick masonry laid in cement, concrete mortar, sheet metal, and hardware cloth of not less than 19-gauge having a mesh not larger than one-half inch (1/2"), and all material for ratproofing shall be of such strength and thickness as to be impervious to rat gnawing. Windows and other openings for light or ventilation, the sills of which are less than thirty inches (30") from the ground or accessible to rats by means of climbing wires or pipes, shall, if open, be covered by hardware cloth conforming to the above gauge and dimensions. All exterior doors shall be protected against the gnawing of rats by the use of materials prescribed above. When closed, all exterior doors shall have a maximum clearance between doors, doorsills and jambs of not exceeding three-eighths inch (3/8"). In all side and rear doors which are left open at night and those which are left open during the day, but infrequently used, shall be installed hardware cloth doors conforming to the above dimensions and equipped with a self-closing device. All concrete floors and curtain walls shall be at least four inches (4") in thickness. (Prior code § 18-22-2)