Except as provided above, any and all expansion of a nonconforming use or addition to a nonconforming structure, including additional stories, shall conform to all height, area, width, yard and coverage requirements for the district in which said use or structure is located. A structure which is nonconforming in terms of height shall not be extended to increase the height. A structure which is nonconforming in terms of side yard can be expanded to the depth of one nonconforming side yard so long as the other side yard related to the expansion complies with the requirements for the district in which the structure is located.