2023 New York Laws › MDW - Multiple Dwelling › Article 3 - Multiple Dwellings--General Provisions › Title 2 - Fire Protection and Safety › 56 - Frame Buildings and Extensions.

§ 56. Frame buildings and extensions. 1. Except as provided in section
  one hundred ninety-three and subdivision seven of this section, no frame
  multiple  dwelling  shall be erected and no frame dwelling not used as a
  multiple dwelling on April  eighteenth,  nineteen  hundred  twenty-nine,
  shall be altered or converted to such use or occupancy.
2.  No  existing  frame multiple dwelling shall be increased in height
  nor shall it be altered to permit a greater occupancy on any story  than
  provided  for  on April eighteenth, nineteen hundred twenty-nine; except
  that, if the walls of such a frame dwelling are faced with brick  veneer
  or  with  another  material  or  combination  of materials having a fire
  resistive rating of at least one hour, and the entrance story thereof is
  occupied by not more than one family, such entrance story may be altered
  so that it may be occupied by not more than two families.
3. No frame building of any kind whatsoever shall be placed  or  built
  upon the same lot with any multiple dwelling.
4.  No  multiple  dwelling  shall be placed or built upon the same lot
  with any frame building.
5. No frame multiple dwelling, no wooden  structure  of  any  kind  or
  class  on  the  same  lot  with  any frame dwelling or with any multiple
  dwelling, and no other building on the same lot with any frame dwelling,
  shall be altered  or  converted  so  as  to  be  enlarged,  extended  or
  increased  in  height  or  bulk or in the number of rooms, apartments or
  dwelling units therein; except that:
a. An extension seventy square feet or less in ground  area  the  side
  walls  of which are of frame and brick filled or of masonry construction
  may be added to any existing frame multiple dwelling if used solely  for
  bathrooms or waterclosets; and
b.  An  extension  constructed  with  fireproof walls may be made to a
  frame building if the first story of such extension is used  solely  for
  business  not  prohibited  by  any  local  law  or ordinance, or if such
  extension contains not more than one living room on any story.  No  yard
  or court shall be diminished by such extension so that its area or least
  dimension is less than required by this chapter for a yard or court of a
  multiple  dwelling  erected  after  April  eighteenth,  nineteen hundred
  twenty-nine.
6. None of the provisions of this section  shall  apply  to  dwellings
  erected under the provisions of article five-a of this chapter.
7.  In any city the department may approve for any such dwelling three
  stories or less in height, the alteration and conversion of that portion
  of said dwelling used as a store or other non-residential use to no more
  than one additional dwelling unit; provided,  however,  that:  (a)  such
  space  has  been  vacant for at least one year, and (b) such space has a
  minimum of three  hundred  square  feet  of  floor  area,  and  (c)  the
  conversion  must be for a class "A" use, and (d) said unit shall contain
  a cooking space and a complete bathroom, and (e) all walls and  ceilings
  of  the  new  dwelling  unit  shall be fire-retarded with one hour rated
  fire-retarding materials, and (f) the height and bulk  of  the  dwelling
  shall  not be increased, and (g) the dwelling will be in full compliance
  with this chapter and other related and local  ordinances,  except  that
  the  owner  of  said  dwelling  shall  be  entitled to consideration for
  variances  permitted  in  subdivision  one  and  subparagraph  five   of
  paragraph  a  of  subdivision  two  of section three hundred ten of this
  chapter for multiple dwellings and buildings existing prior to  November
  first, nineteen hundred forty-nine.