Excessive similarity to any other structure existing, or for which a permit has been issued, in respect to one or more of the following features of exterior design and appearance: apparently identical front, side or other elevations visible from the street, substantially identical size and arrangement of either doors, windows, porticoes or other openings or breaks in the elevation facing the street, including reverse arrangement; or other significant identical features of design, such as, but not limited to, material, roof line, height or other design elements.