No modifications or additions to a nonconforming use shall be permitted unless they are made in conformity with the provisions of this section. For the purpose of this section the words "modification" and "addition" shall include, but not be limited to, any alteration, addition, modification, rebuilding or replacement of any such existing structure or accessory use. Ordinary maintenance repairs are not considered structural repairs, modifications, or additions. Such ordinary maintenance repairs include internal and external painting, decorating, paneling, and the replacement of doors, windows and other structural components.