In all cases where a fence or wall shall hereafter be erected contrary to the provisions of this section, the director of public works shall forthwith notify the owner or agent or lessee of the land on which same is located, or the contractor engaged in erecting same, and shall specify briefly in such notice in what manner such fence or wall violates the provisions of this article, and the director of public works shall require the person so notified to forthwith make such fence or wall conform to and comply with the provisions of this article, specifying in such notice the time within which such work shall be done.