The designating official shall assign numbers to all public or private ways now existing or hereafter established, which have not been named or numbered heretofore; provided, that no name or number shall be assigned to a private road or way unless the same shall be servient to one or more properties other than the tract of which it is a portion and unless an easement appurtenant has been granted by recorded deed. (1961 code § 10.08.020.)