All uses of buildings, structures, and land established hereafter; all buildings, structures and improvements to land constructed or erected hereafter; and all existing buildings and structures raised, moved, reconstructed, extended, enlarged, or altered hereafter shall conform to all regulations of this title and all amendments hereto pertaining to the zoning district in which such buildings, structures, and land are located. However, where a building permit for a building or structure has been issued in accordance with law prior to the effective date hereof, or any amendment hereto, and where construction has begun within six (6) months of such effective date and diligently prosecuted to completion, said building or structure may be completed in accordance with said permit; and further, upon completion, may be occupied for the use originally designated, subject to the provisions on nonconforming uses, chapter 11 of this title. (1990 Code §21.1.070)