Ordinary maintenance. Ordinary maintenance repairs, including repairs reasonably necessary to prevent the deterioration of a structure, and remodeling of a legal, nonconforming structure are permitted, as well as necessary nonstructural repairs and alterations that do not extend, enlarge, or intensify the nonconforming structure. Ordinary maintenance repairs and remodeling include internal and external painting, decorating, paneling, the addition of acoustical ceilings, the installation of heating, electricity, plumbing (including fixtures) or insulation, and the replacement of doors, windows, and other nonstructural components.