2006 New York Code - Altered Buildings.

 
    §  27-215  Altered buildings. Except as permitted under the provisions
  of section 27-218 of this article, no building hereafter altered  so  as
  to  change  from  one  occupancy group to another, either in whole or in
  part, or so as to affect any existing means  of  egress,  or  so  as  to
  increase  the number of habitable rooms in the building, and no building
  hereafter  altered  for  which  a  certificate  of  occupancy  has   not
  theretofore  been  issued,  shall be occupied or used unless and until a
  certificate of occupancy shall have  been  issued  certifying  that  the
  alteration  work  for  which  the  permit  was issued has been completed
  substantially in accordance with the approved plans and  the  provisions
  of  this code and other applicable laws and regulations. If the building
  was not required to be vacated, either in whole or in part,  during  the
  course  of  the  alteration  work,  the occupancy or use of the building
  shall not continue more than thirty calendar days  after  completion  of
  the  alteration work, unless a certificate of occupancy has been issued,
  as above provided.