A BUILDING, whether high rise or low rise:
(1) Which on 4/1/1984 is complete or under construction, or
(2) For which an application for approval of plans has been filed with the department prior to 10/1/1984 and construction commenced prior to 4/1/2986, provided that those requirements of this code applicable to existing buildings classified in the same occupancy group as the proposed building shall be complied with in accordance with the time limitations set forth in this code. (See New NYC Construction Codes Definition of EXISTING BUILDING OR STRUCTURE)