N.Y.C. Admin. Code § 28-101.4.5.1: § 28-101.4.5.1 Changes in scope of work.

In cases where changes in the scope of work during the course of construction would result in increasing the floor surface area at the completion of construction by more than 110 percent, over the amount of existing floor surface area as determined pursuant to section 28-101.4.5, such entire building shall be made to comply with the provisions of this code as if hereafter erected and such work shall be refiled as a new building application in accordance with the provisions of section 28-105.2.

Exception: Work to the extent necessary to relieve an emergency condition may be performed prior to amending plans or obtaining a new permit pursuant to sections 28-105.4.1 and 28-105.12.2.