2006 New York Code - Stairs In Non-fireproof Tenements.

 
    §  235.  Stairs  in  non-fireproof  tenements.  1. Every non-fireproof
  tenement erected after May fifteenth, nineteen hundred  two,  containing
  more  than  twenty-six  apartments or suites of rooms above the entrance
  story shall have an additional stair  for  every  additional  twenty-six
  apartments  or  suites or fraction thereof; except that if such tenement
  contains not more than thirty-six apartments above the  entrance  story,
  in  lieu  of  an  additional  stair the stairs, stair halls and entrance
  halls throughout the entire tenement may each be at least one-half wider
  than is specified in  sections  two  hundred  thirty-four,  two  hundred
  thirty-seven and two hundred thirty-eight.
    2. The number of apartments on any story in any non-fireproof tenement
  may  be  altered,  if  the  number  of living rooms on such story is not
  increased by more than twenty per centum. If the number of living  rooms
  on any story or section thereof above the entrance story exceeds twenty,
  there  shall  be  an  additional stair for each twenty rooms or fraction
  thereof on any such story or section thereof, except that if the  number
  of  living rooms on any such story or section does not exceed thirty, in
  lieu of an additional stair one stair and every  public  hall  connected
  therewith  may  be at least one-half wider than is specified in sections
  two hundred  thirty-four,  two  hundred  thirty-seven  and  two  hundred
  thirty-eight.
    3.  Whenever  the  total  number  of  rooms,  exclusive  of bathrooms,
  water-closet compartments, and cooking spaces less  than  eighty  square
  feet  in  area,  in  any  non-fireproof  tenement  or section thereof is
  decreased through the process of an alteration, the number of apartments
  may be altered and the  provisions  of  this  section  which  relate  to
  additional stairs shall not be applicable.