All structures shall be located on a lot; and, except as otherwise provided in this ordinance, in the A-1, A-2, A-4, R-1, R-2, R-3, R-4, R-5, R-6, R-7, R-8 and C-2 districts, only one principal structure shall be located, erected or moved onto a lot. The number, size and type of accessory structures shall be governed as specified in each district and section 12.17 of this ordinance. All lots shall abut upon a public street, easement of record or other officially approved means of access and no zoning permit shall be issued for a lot which abuts a public street dedicated to only a portion of its proposed width and located on that side thereof from which the required dedication has not been secured. [Code § 12.10-1.]