Nonconforming signs. Wall and freestanding signs in existence on the date of enactment of this chapter that do not conform to the dimensions or placement described in this section may continue to be used as legal nonconforming signs. A legal nonconforming sign shall not be enlarged, or altered, and if it is removed from its location for other than routine cleaning, maintenance or repainting, it shall be made to conform to this chapter. Any increase in size or change in the design, style, location, materials, shape, height or location of a nonconforming sign shall not be permitted. Any nonconforming sign that is damaged or destroyed, for a loss of 50% or more of its value, as determined by the Building Inspector, by fire or other casualty shall not be restored, reconstructed or replaced except by a sign that conforms to this requirements of this chapter.