Group dwellings shall be considered as one (1) building for the purpose of front, side and rear yard requirements, the entire group as a unit requiring one (1) front, one (1) rear and two (2) side yards as specified for dwelling structures. The minimum distance between structures shall be fifteen (15) feet for single-story buildings, twenty (20) feet for two (2) story buildings and twenty-five (25) feet for three (3) or more story buildings. (PZSC § 03-09-001)