Section 260. One and two-story frame dwellings; area limitation

A frame
  dwelling not exceeding two stories in height erected pursuant  to  plans
  filed  after April first, nineteen hundred fifty-nine, and containing an
  area greater than three thousand square feet must, in  addition  to  any
  other  applicable  provisions of this article, comply with the following
  provisions:
    1. Fire-stopped partitions shall be constructed between apartments  in
  such  dwelling so as to prevent the passage of fire, smoke or gases from
  one apartment to another.
    2. No section of such dwelling shall contain more than three  thousand
  square  feet.  Each  such  section  shall  be  separated  from all other
  sections of the dwelling by fire walls of  masonry  or  other  materials
  having  a  fire  resistive  rating  of at least two hours. Such wall (1)
  shall be unpierced except for  openings  for  heat,  utility  and  other
  service  lines  and  ducts  with such openings sealed with incombustible
  materials (2) shall extend continuously from the  floor  of  the  lowest
  level  of  the  dwelling,  to  at  least two feet above the level of the
  finished roof and (3) be fire-stopped at floors and roof in such  manner
  as  to  prevent  the  passage  of fire, smoke or gases between sections.
  Where there is a peaked or sloped roof, such wall may terminate  at  the
  top of the roof boards.