Section 101. Requirements for fireproof construction

1. Every such dwelling
  exceeding six stories or seventy-five feet in height shall be fireproof.
  No  multiple  dwelling  shall  be altered so as to exceed either of such
  heights without being made fireproof.
    2. In a fireproof multiple dwelling the walls,  floors,  roof,  stairs
  and   public  halls  shall  all  be  fireproof  except  as  provided  in
  subdivision three. No beams, lintels or other structural  members  shall
  be  of wood.  No wood or other inflammable material shall be used in any
  of the partitions, furrings or ceilings. For the portion of  a  multiple
  dwelling  more than one hundred fifty feet above the curb level, no wood
  shall be used except as provided in subdivision  three  and  except  for
  interior trim of windows.
    3. The foregoing requirements shall not be construed as prohibiting:
    a.  Elsewhere  than  within,  or in the openings to, the public halls,
  stairs and shafts, the  use  of  wood  for  sleepers,  grounds,  nailing
  blocks,  underflooring,  finish  flooring,  interior  doors  with  their
  assemblies and saddles, floor base not more than  one  foot  in  height,
  picture  and  wall  moulding,  shelving,  closet  and  kitchen fixtures,
  cupboards, cabinets and wardrobes.
    b. The use of wood for windows and for interior trim and finish backed
  solidly against, or filled with, incombustible material when located not
  more than one hundred fifty feet above the curb level and elsewhere than
  within, or in the openings to, the public halls, stairs and shafts.
    c. The use within apartments of wood for  decorative  wall  panelling,
  wainscoting,  mantels  or  other  interior  finish,  and  the  use in an
  entrance hall of wall panelling or wainscoting made of fireproof wood or
  other material capable of successfully withstanding standard fire  tests
  prescribed  in  the  local building code and in a manner approved by the
  department.
    d. Where fireproof doors are required, the use for  such  doors,  with
  their  assemblies  and  saddles, of material and construction capable of
  successfully withstanding a one-hour standard fire  test  prescribed  in
  the  local  building  code  and  in a manner approved by the department.
  Should any door required to be fireproof be found to  have  deteriorated
  so that it shall after installation fail to conform to the standard fire
  tests  prescribed,  such door shall be removed by the owner and replaced
  by him with a door capable of successfully withstanding such tests.
    4.  All  materials  combustible  in  their  natural  state  which  are
  constructed,  processed  or  protected  so  that  they  will not support
  combustion shall, before being installed in a multiple dwelling for  any
  of  the  uses  herein  specified,  be permanently identified by label or
  marking with the name of the manufacturer and the year of manufacture in
  a manner approved by the department.
    5. When required to be fireproof,  any  outer  wall  or  any  wall  or
  partition  which  carries  any load in addition to its own weight shall,
  unless otherwise in this chapter expressly required, be  constructed  of
  materials capable of successfully withstanding a four-hour standard fire
  test  prescribed  in the local building code and in a manner approved by
  the department. When required to be fireproof,  any  wall  or  partition
  which  carries  only  its own weight, other than an outer wall, shall be
  constructed of materials capable of successfully withstanding a one-hour
  standard fire test prescribed in the local building code and in a manner
  approved by the department.