§ 264. Fireproof building. "Fireproof building" means a building conforming to the following requirements: 1. All exterior walls shall be constructed of brick, or stone, or concrete, or cinder block, or concrete block, or tile, or terra cotta or such other material as shall be specified in the rules of the board. The board shall determine and specify in its rules such requirements as it deems necessary for the construction of exterior walls. 2. All floors and roofs shall be built of brick, or cinder block, or concrete block, or tile, or terra cotta, or reinforced concrete supported by steel or reinforced concrete beams and girders. The board shall determine and specify in its rules such other materials, the manner of construction of floors and roofs and such other requirements as may be deemed necessary to carry into effect the intent of this chapter. 3. All structural metal shall be encased in fireproof material, of such thickness as shall be specified in the rules of the board. 4. All vertical openings leading from one floor to another, except one created by a mezzanine floor, shall be enclosed by fireproof or fire-resisting materials in a manner conforming to rules adopted by the board. 5. All stairways, landings, hallways, floor surfaces, furring, ceilings, partitions, sash, trim, window frames, doors and other interior finish, shall be constructed of incombustible material; but nothing in this section shall prevent the use of such combustible materials as the board shall determine and specify in its rules. Such rules shall also specify the circumstances or conditions under which combustible flooring, trim, acoustical material, insulating material or other interior finish may be used or applied to floors, walls, partitions or ceilings of fireproof buildings. 6. All windows shall be fire windows except: a. In buildings less than seventy feet in height erected after October first, nineteen hundred and thirteen, where the windows are located more than thirty feet from another building or open on a court or space more than thirty feet wide; b. In buildings less than one hundred and fifty feet in height erected before October first, nineteen hundred and thirteen, where the windows are located more than thirty feet from another building. c. Fire windows may be provided with plate glass not less than one-fourth of an inch in thickness, no light of which shall exceed seven hundred and twenty square inches in area.

(1) If the windows are located more than thirty feet horizontally or fifty feet vertically from the nearest opening in the wall of another building.

(2) If the windows are located more than fifty feet in a vertical direction above the roof of a building within a horizontal distance of thirty feet of the wall in which the said windows are located. 7. Partitions. All partitions in the interior of fireproof buildings shall be of incombustible material. Nothing in this section shall prevent the use, in a building equipped with automatic sprinklers, of subdividing partitions of wood, or of wood and glass, in spaces used solely for office or show-room purposes, provided, however, that where such spaces are contiguous to any room or rooms in which manufacturing is carried on, such spaces shall be separated from such room or rooms by a dividing partition which, including doors, is constructed of incombustible material.