Rear yard. There shall be a rear yard of at least 100 feet. The rear yard may be used for off-street parking, provided, however, no parking area shall be nearer than 10 feet to any building excepting residential buildings or 10 feet to any nonresidential property line, or 100 feet from any residence zone boundary line. The aforesaid separation area between the parking area and any adjoining residence zone boundary line shall constitute a buffer zone.