Maintenance. Every sign, including those signs erected prior to the adoption of this chapter, shall be maintained in a safe, presentable and good structural material condition at all times, including the replacement of defective parts, painting, repainting, cleaning and other acts required for the maintenance of said sign. The owner of any property on which a sign is located and those responsible for maintenance of the sign shall be equally responsible for the conditions of the area in the vicinity of the sign and shall be required to keep this area clean, sanitary and free from noxious or offensive substances.