Section 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.