N.Y.C. Admin. Code § 27-498: § 27-498 Application.

This section shall apply to the construction, alteration, and use of all outdoor signs and display structures, together with their appurtenant and auxiliary devices.

(a) No sign may be hung or attached upon or on the outside of any building unless such work is performed by or under the supervision of a licensed sign hanger.

(b) No sign shall be erected until a permit therefor has been obtained from the commissioner in accordance with the provisions of article two of subchapter eleven of this chapter.