No lot shall be so reduced in area by conveyance of a portion thereof as to make any open space of such lot less than the minimum requirements prescribed herein, provided that:
(a) Such requirements shall not be construed to prevent the sale of an individual unit of a multiple dwelling.
(b) A lot having more than one existing principal building may be divided into separate parcels each having at least one principal building.
(Ord. 30-1985. Passed 6-25-85.)