NY Mult Dwell L § 218 (2021)
2021 New York Laws MDW - Multiple Dwelling Article 7 - Tenements Title 1 - Light and Air 218 - Alterations.

§  218.  Alterations.  1. Any non-fireproof tenement erected after May   fifteenth, nineteen hundred two, having apartments extending from street   to yard and having one or more outer courts on a side lot line four feet   or more in width or inner courts which alone or together with  adjoining   courts  are  eight  feet  or more in width and twelve feet six inches or   more in depth, may be altered into  apartments  opening  either  on  the   street  or  the  yard,  provided  all  such altered apartments also have   windows opening on such a court. All such altered  apartments  shall  be   provided  with  a  second  means  of  egress  as required by section two   hundred thirty-one. The entrance and stair halls of such tenement  shall   be fire-retarded.2.  No  room  in  the  cellar  or  basement  of  any tenement shall be   constructed or altered to be occupied for living purposes unless all  of   the  conditions  of  section  thirty-four  and  of  subdivision eight of   section twenty-six in regard to multiple dwellings erected  after  April   eighteenth, nineteen hundred twenty-nine, are complied with, except that   the  minimum  depths  of  yards  and  courts prescribed for tenements in   subdivision one of section two hundred twelve shall be  substituted  for   the minimum depths referred to in section thirty-four.3.  Any  additional  room or hall constructed or created in a tenement   shall comply in  all  respects  with  the  provisions  of  this  article   respecting  rooms  or halls in tenements erected after April eighteenth,   nineteen hundred twelve, except that in any tenement erected after April   fourteenth, nineteen hundred three, such rooms or halls may  be  of  the   same height as the other rooms or halls on the same story.4.  The  number  of  apartments or suites of rooms on any story in any   tenement erected after April  twelfth,  nineteen  hundred  one,  may  be   altered  so  as  to  increase  or  decrease  the  number of living rooms   provided such dwelling shall conform with the applicable  provisions  of   sections two hundred thirty-five and two hundred thirty-six.5.  If  the  number  of  apartments  or suites of rooms in any old-law   tenement is increased, the entrance hall and both sides of the walls  of   the  stair halls adjoining the altered apartment shall be fire-retarded,   the stairs shall extend to the roof and there shall be no inside  stairs   from  the  entrance  story  to a cellar, or to a basement or other story   below the entrance story. However, such inside stair  may  be  permitted   provided such stair is constructed of incombustible material, has closed   risers, is enclosed between the entrance story and the next lowest story   with  fireproof  materials having a standard fire-resistive rating of at   least three hours, and has fireproof doors and door  assemblies  at  the   top  and bottom with the doors and door assemblies at the top and bottom   with the doors self-closing. The soffit of any stair  immediately  above   an  inside  cellar  stair  shall be fire-retarded and the jib partitions   enclosing such cellar stair at the first story shall be of incombustible   material or fire-retarded on both sides with materials having a standard   fire-resistive rating of at least one hour.6. If any old-law tenement shall be so  altered  as  to  increase  the   number  of  rooms  therein  by one-third or more, or if such tenement is   increased both  in  number  of  rooms  and  in  height  and  after  such   alteration  is more than four stories or parts of stories above the curb   level, or if such tenement is  over  three  stories  in  height  and  is   combined  with  another  old-law  tenement  and the combined area on any   story exceeds three thousand square  feet,  the  stair  halls,  entrance   halls  and  other  public  halls  of the whole dwelling shall be made to   conform to the requirements of subdivision two of  section  two  hundred   thirty-three  and  sections  two  hundred  thirty-four  to  two  hundred   thirty-eight inclusive, except that such  combined  tenements,  if  over    three  stories  in  height,  shall have in the roof a fireproof bulkhead   with a fireproof self-closing door.7.  In  lieu  of fire retarding required under subdivision five, there   may be installed in public halls an automatic dry pipe valve system  or,   where  halls are heated, an automatic wet pipe system. Where a sprinkler   system is installed it shall be equipped on each  story  with  heads  in   such  number and spaced to protect the complete area of the public halls   and stairs and shall be constructed, located and arranged on every stair   and entrance hall and in every closet opening therefrom in such a manner   as the department may require. Such sprinkler system shall be maintained   continuously in good repair and serviceable condition.