Cloth signs may have a structural frame of wood which is free from knots, cross-grain and other structural defects. Such frame shall be so constructed that it will have adequate strength to resist all wind loads to which it may be subjected and shall be properly fastened to the building. Cloth signs and banners placed against building walls shall be flameproofed if the area covered by such sign or banner exceeds one hundred square feet. (Ord. 89-3 (part), 1989)