New buildings and vacant land. Construction of any building to be erected hereafter shall not be commenced, nor shall vacant land be occupied or used in whole or in part, until a zoning certificate of use is issued by the Code Enforcement Officer or his deputy; this certificate of use shall certify that such use, or such building and the location and use, conform to the provisions of this chapter. However, this section shall not apply to construction on a farm or to the usual buildings appurtenant or necessary to a farm operation; this section shall apply to buildings on a farm used for dwelling purposes.