Section 142. Sub-curb uses

1. When such a dwelling is more than eighty feet
  in  height  measured from the lowest point of the yard or of any curb on
  which any part of the dwelling faces, whichever is lower, and  any  room
  in  such  dwelling below the level of the highest curb which any part of
  such dwelling faces is occupied for  living  purposes  as  permitted  in
  paragraph  f  of subdivision one of section thirty-four, the yard at the
  level of such highest curb shall be set back so as to be at least  eight
  feet  greater  in  depth  than the yard below such level unless the yard
  opens directly upon a street.
    2. If such a dwelling is erected upon an interior lot running  through
  from street to street, the wall of the dwelling facing the lowest street
  shall,  at  the  level  of  the  highest  curb on which any part of such
  dwelling faces, be set back at least eight feet.
    3. The setback of the yard  or  wall  required  by  each  of  the  two
  preceding subdivisions shall be a fire-terrace. Nothing herein contained
  shall  be  construed  to  permit  a yard of smaller dimensions below the
  level of such fire-terrace than required by paragraph f  of  subdivision
  one of section thirty-four.
    4.  From  each apartment below the level of such highest curb at least
  one means of egress shall lead directly to such fire-terrace in a manner
  approved by the department. Such fire-terrace shall be  protected  by  a
  guard  railing  approved  by  the  department, and shall afford safe and
  unobstructed access  either  directly  to  a  street  or  to  a  covered
  fireproof  passage at least three feet in width and seven feet in height
  leading directly and without obstruction to a street.
    5. In all portions of such dwellings below the level  of  the  highest
  curb  all structural members, partitions, furrings and ceilings shall be
  constructed of incombustible materials.
    6. Apartments may also be occupied for living purposes in cellars  and
  basements  in  accordance  with  the  provisions  of  subdivision six of
  section thirty-four.