Section 163. Construction and arrangement

Garden-type maisonette dwelling
  projects may be erected on condition that they comply with the following
  provisions:
    1. The  dwelling  units  in  such  projects,  together,  or  in  their
  aggregate,  do  not exceed in superficial area thirty-five per centum of
  the area of the site or plot upon which such projects are erected.
    2. The units in such projects do not exceed two stories in height.
    3. Each section contains not more than two apartments in any unit.
    4. Every one or two-family unit is separated from all other such units
  by  an  unpierced  partition   constructed   of   materials   having   a
  fire-resistive  rating  of  at least one hour and such partition extends
  from the first floor above the basement or cellar of the dwelling to the
  top of the roof boards in such manner as to prevent the passage of fire,
  smoke or gases between units.
    5. a. A project section shall  not  be  constructed  of  units  which,
  together,  are  of a greater area than three thousand square feet unless
  divided by unpierced fire walls of masonry or other materials  having  a
  fire-resistive  rating  of  at  least  three  hours.  Such wall shall be
  continuous from the floor of the lowest level of the dwelling to the top
  of the roof boards and be fire-stopped at floors and roof in such manner
  as to prevent the passage of fire, smoke or gas between areas.
    b. Fire walls shall extend at least two feet above the  level  of  the
  finished  roof  or,  in  lieu thereof, where there is a peaked or sloped
  roof, the ceiling of the attic of  all  units  comprising  such  section
  shall  be covered with gypsum plaster-boards three-eighths of an inch in
  thickness or with other materials having the same fire-resistive rating.
    6. The facing of the exterior walls shall be of brick veneer not  less
  than four inches in thickness or may be of one or a combination of other
  materials;  and  the interior facing of such walls shall be covered with
  one-half-inch thick plaster boards and three-eighths-inch  thick  sanded
  gypsum  plaster or a combination of other materials which, when combined
  with the exterior materials shall have a  fire-resistive  rating  of  at
  least one hour.
    7.  Cellar  ceilings  throughout  shall be covered with gypsum plaster
  boards three-eighths of an inch in thickness  or  with  other  materials
  having  the same fire resistive rating. A heating plant located within a
  section shall be completely enclosed with incombustible materials having
  a fire resistive rating  of  at  least  three  hours  and  all  openings
  therefrom  to  other  parts  of  the  dwelling  shall  be  equipped with
  fire-proof doors and assemblies with the doors self closing.
    8.  Concealed  vertical  and  horizontal  draft  openings   shall   be
  fire-stopped with incombustible materials.