No lot shall be reduced in size so as to make the width or total area of the lot, or any yard, or any other open space, less than the minimum required by this chapter. No part of a yard or other open space provided about any building or structure for the purpose of complying with the provisions of this chapter shall be included as a part of a yard or other open space required under this chapter for another building or structure. Off-street parking and loading areas may occupy part of any required yard or open space except as specified in Section 165.42 of this chapter.