In any district in connection with every building or part thereof hereafter erected, having a gross floor area of 10,000 square feet or more, which is to be occupied by manufacturing, storage, warehouse, goods display, retail store, wholesale store, market, hotel, hospital, mortuary, laundry, dry cleaning or other uses similarly requiring the receipt or distribution by vehicles of material or merchandise, there shall be provided and maintained on the same lot with such building at least one off-street loading space plus one additional such loading space for each 20,000 square feet or major fraction thereof of gross floor area so used in excess of 10,000 square feet. Each loading space shall be not less than twelve (12) feet in width and forty (40) feet in length. Such space may occupy all or any part of any required yard or open space, except where adjoining an “R” district, it shall be set back at least twenty (20) feet and effectively screen planted.