In S Slope Districts, the following regulations shall apply.
On each lot not occupied by a building or structure and on each
lot upon which a building is hereafter erected, enlarged or repaired,
there shall be provided and maintained a lot area, yards and other
open spaces which shall be not less than prescribed as follows.
A. Front yard depth: not less than 20 feet.
B. Side yard widths.
(1) Interior lot: not less than three feet on each side of the main building.
(2) Corner lot: not less than 20 feet on all yards abutting on a street
or alley.
(3) Rear yard depth: not less than 20 feet. (Exclusive of any portion
of depth to be used for permitted accessory uses or buildings.)