N.Y.C. Admin. Code § 27-978: § 27-978 Definitions.

For the purposes of this article:

a. an existing building is one which is within occupancy group J-1, occupancy group J-2 or occupancy group J-3 and for which plans have been approved by the department on or prior to December thirty-first, nineteen hundred eighty-one.

b. an improvement or alteration is a physical change in an existing structure other than painting, repairs and normal replacement of maintenance items.

c. a building shall be deemed to have been substantially improved or altered if:

1. the cost of improvement or alteration exceeds the sum of one hundred fifty thousand dollars, or

2. in either occupancy group J-1 or occupancy group J-2, fifty percent or more of the dwelling units or square feet of the structure are improved or altered and the cost of such improvement or alteration exceeds the sum of fifteen thousand dollars per dwelling unit, or

3. there has been a change in the occupancy or use of the structure.