N.Y.C. Admin. Code § 27-341: § 27-341 Fire separations.

Fire separations shall be constructed of materials or assembly of materials having at least the fire-resistance ratings required by table 5-1.

(a) Different tenancies. Different tenant apartments, suites, stores, offices, or other spaces that are not separated from each other by fire divisions, shall be separated from each other by fire separations having at least the fire-resistance rating prescribed in table 5-1, but in no case less than one hour, and shall continue through any concealed spaces of the floor or roof construction above.