Section 9. Buildings converted or altered

1.  On or after July first,
  nineteen hundred fifty-two, no multiple dwelling shall  be  enlarged  or
  its  lot  diminished so that the yard or other unoccupied areas shall be
  diminished in size or  area  below  the  minimum  requirements  of  this
  chapter.
    2.  A  building  not  a dwelling, if converted on or after July first,
  nineteen hundred fifty-two, to  a  multiple  dwelling,  shall  thereupon
  become  subject  to all the provisions of this chapter applicable to new
  multiple dwellings of like class and kind. "Class" shall mean the use of
  a multiple dwelling for either permanent or transient occupancy or both.
  "Kind" shall mean  the  type  of  construction  of  a  building,  either
  fireproof or non-fireproof.
    3.  No dwelling shall be altered or converted so as to be in violation
  of any provision of this chapter relating to dwellings of like class and
  kind, and, except as provided in subdivision four, a  dwelling,  altered
  or converted to be occupied primarily for permanent-residence use, shall
  comply  with  article  three;  and a dwelling converted or altered to be
  occupied primarily for transient use shall comply with article four.
    4. If any multiple dwelling three or more stories in height is altered
  after July first, nineteen hundred fifty-three so  as  to  increase  its
  height  or  bulk  for living purposes or so as to increase the number of
  living rooms by more than twenty per centum, such dwelling shall be made
  to conform to the requirements of  this  chapter  with  respect  to  new
  dwellings of like class and kind erected after such date.
    5.  It  shall  be  unlawful  to convert a frame dwelling to a multiple
  residence, except that a frame dwelling not more than  two  stories  and
  attic  in  height  and  erected  before  July  first,  nineteen  hundred
  fifty-two, as a one-family or two-family residence may be converted to a
  multiple dwelling for permanent  occupancy  by  complying  with  article
  three; and if such residence is converted to be occupied, as a rule, for
  transient use, it shall comply with article four.