Certain lots, structures, developed sites and uses of land or structures which were lawful at the time of their establishment are made nonconforming under the provisions of this Code. This chapter provides for the continuance of nonconformities, subject to regulations limiting their completion, restoration, reconstruction, extension, and substitution. While it is the intent of this Code that such nonconformities be allowed to continue until removed, they should not be encouraged to survive. It is further the intent of this Zoning Code that nonconformities shall not be used as grounds for adding other structures prohibited elsewhere in the same zoning district, nor shall nonconformities be enlarged, extended or expanded except as otherwise provided herein.