It shall be unlawful for an owner to use or permit the use of any building or part thereof hereafter erected, altered, converted, or enlarged, wholly or in part, until a certificate of occupancy, applied for at the time of application for a building permit, shall have been issued by the construction official. Such certificate shall show that such building or part of the building and the proposed uses thereof conform to the requirements of this chapter. It shall be the duty of the construction official to issue a certificate of occupancy only when he is satisfied that the building, or part of the building, and the proposed use thereof so conforms.