N.Y.C. Admin. Code § 27-268: § 27-268 Classification.

When a building or space is used for an occupancy not specifically provided for in this code, or when its classification is otherwise uncertain, such building or space shall be included in the occupancy group that it most nearly resembles with respect to the existing or proposed life and fire hazard, and it shall be so classified by the architect or engineer subject to the approval of the commissioner.