No building or buildings, exclusive of accessory buildings, porches, entries, garages and terraces, shall contain less than 800 square feet gross floor area. No building or buildings, exclusive of accessory buildings, porches, entries, garages and terraces, shall contain more than 10,000 square feet gross floor area, if used as a permitted use, nor more than 30,000 square feet gross floor area, if used as a special exception use.