Section 27-2087. Occupancy of cellars and basements in one- and two-family dwellings

a. Cellar occupancy:    No room in the cellar of a one- or two-family dwelling shall be rented
  and no member of the family or families occupying the dwelling shall use
  such room for sleeping,  eating  or  cooking  purposes,  except  that  a
  secondary kitchen for accessory cooking may be located in the cellar.
    b. Use of basement by occupants of the dwelling:
    A  room  in  the  basement  of  a  one-  or two-family dwelling may be
  occupied for living purposes by members of the  family  or  families  in
  conjunction  with  their  occupancy  of  the  dwelling  if the following
  conditions are met:
    (1) Such room complies with all of the requirements of this  code  for
  rooms  which  are not located in the cellar or basement; except that the
  minimum ceiling height required in one family dwellings shall  be  seven
  feet.
    (2)  Whenever the department determines that the subsoil conditions on
  the lot so require, the basement or other lowest floor and all  exterior
  walls as high as the ground level shall be dampproofed and waterproofed.
    c. Rental of basement:
    An  apartment,  in  the  basement  of  a  one-family  dwelling  may be
  occupied, unless otherwise prohibited under the zoning resolution of the
  city of New York, if it meets the requirements of subdivision b and  all
  of the following conditions:
    (1)  Such  basement  occupancy is limited to one family which, for the
  purposes of this section, shall not include boarders.
    (2) Every room shall have a window complying with the requirements  of
  section 27-2062 of article one of this subchapter.
    (3)  The  bottom  of any yard or other required open space shall be no
  higher than six inches below the window sill of any required  window  in
  any room.
    d.  Conversion  to multiple dwelling. No private dwelling of more than
  three stories in  height  which  was  erected  after  April  eighteenth,
  nineteen  hundred  twenty-nine shall be converted to a multiple dwelling
  unless it complies with all the provisions of the multiple dwelling  law
  applicable to dwellings erected after April eighteenth, nineteen hundred
  twenty-nine.