No building shall hereafter be erected and no existing building shall be moved, structurally altered, rebuilt, added to or enlarged, nor shall any land be used for any purpose other than those included among the uses listed as "Permitted Uses" in each zone by this Chapter and meeting the requirements set forth in the attached Schedule (Subsection 18-5.1). Furthermore, no open space contiguous to any building shall be encroached upon or reduced in any manner, except in conformity to the area and bulk requirements, off-street parking and loading requirements, and all other requirements and regulations designated either in this Chapter or Schedule for the zone in which such building or space is located. In the event of any unlawful encroachment or reduction such building or use shall be deemed to be in violation of this Chapter and the Certificate of Occupancy shall become void.