(a) The area for every parcel for a manufacturing operation shall be not less than necessary to provide the required yards and off-street parking, and not more than 50% of the lot area shall be covered with buildings.
(b) Provided, however, for a manufacturing operation of which at least 75% of the buildings were constructed prior to October 15, 1956, the Commission may by a conditional use permit allow the lot area covered by buildings to be increased to 65% if it determines that:
(1) No additional land can be readily acquired to maintain a 50% yard area after the construction of additional buildings, and the construction of additional buildings will not create additional fire, explosion, or other hazards, and every reasonable effort has been made by the applicant to create sufficient off-street parking, and loading and unloading facilities, or
(2) The nature of the manufacturing operation is such that coverage of the area by buildings is great in comparison to the needed employee or customer parking facilities, or loading and unloading facilities, or
(3) The nature of the manufacturing operation is such that much of the storage of goods or vehicles is in buildings.
(1980 Code 151.77)