Within the districts established by the Zoning Code or amendments that may later be adopted, there exist lots, structures, and uses of land and structures which were lawful before the Zoning Code was adopted or amended, but which would be prohibited, regulated, or restricted under the terms of the Zoning Code or future amendment. It is the intent of this chapter to permit these nonconformities to continue until they are removed, but not to encourage their survival. It is further the intent of this chapter that nonconformities shall not be enlarged upon, expanded, or extended, or be used as grounds for adding other structures or uses prohibited elsewhere in the same district. To avoid undue hardship, nothing in this chapter shall be deemed to require change in the plans, construction, or designated use of any building on which actual construction was lawfully begun prior to the effective date of adoption or amendment of the Zoning Code and upon which actual building construction has been diligently carried on. Actual construction is hereby defined to include the placing of construction materials in permanent position and fastened in a permanent manner; except that where demolition or removal of an existing building has been substantially begun preparatory to rebuilding, such demolition or removal shall be deemed to be actual construction, provided that such work shall be diligently carried on until completion of the building involved.

   In any district in which single-family dwellings are permitted, notwithstanding limitations imposed by other provisions of the Zoning Code, a single-family dwelling and customary accessory buildings may be erected on any single lot of record at the effective date of adoption or amendment of the Zoning Code. This provision shall apply even though such lot fails to meet the requirements for area or width, or both, that are generally applicable in the district.

   Where, at the effective date of adoption or amendment of the Zoning Code, lawful use of land exists that is made no longer permissible under the terms of the Zoning Code as enacted or amended, such use may be continued subject to the following provisions:

   1.   No such nonconforming use shall be enlarged or increased or extended to occupy a greater area of land than was occupied at the effective date of the adoption or amendment of the Zoning Code.

   2.   No such nonconforming use shall be moved, in whole or in part, to any other portion of the lot or parcel occupied by such use at the effective date of the adoption or amendment of the Zoning Code.

   3.   If any such nonconforming use of land ceases for any reason for a period of more than six months, any subsequent use of such land shall conform to the regulations specified by the Zoning Code for the district in which such land is located.

   If a lawful use of a structure, or of structure and premises in combination, exists at the effective date of adoption or amendment of the Zoning Code that would not be allowed in the district under the terms of the Zoning Code, the lawful use may be continued subject to the following provisions:

   1.   No existing structure devoted to a use not permitted by the Zoning Code in the district in which it is located shall be enlarged, extended, constructed, reconstructed, or structurally altered except in changing the use of the structure to a use permitted in the district in which it is located.

   2.   Any nonconforming use may be extended throughout any of the parts of a building which were manifestly arranged or designed for such use at the time of adoption or amendment of the Zoning Code, but no such use shall be extended to occupy any land outside such building.

   3.   If no structural alterations are made, any nonconforming use of a structure, or structure and premises, may be changed to a more restricted classification.

   4.   When a nonconforming use of a structure, or structure and premises in combination, is discontinued or abandoned for six months, the structure, or structure and premises in combination, shall not thereafter be used except in conformance with the regulations of the district in which it is located.

   5.   Where nonconforming use status applied to a structure and premises in combination, removal, or destruction of the structure shall eliminate the nonconforming status of the land.

   On any building devoted, in whole or in part, to any nonconforming use, work may be done on ordinary repairs, or on repair or replacement of non-bearing walls, fixtures, wiring, or plumbing, provided that the cubic content of the building as it existed at the time of passage or amendment of the Zoning Code shall not be increased. Nothing in this chapter shall be deemed to prevent the strengthening or restoring to a safe condition of any building or part thereof declared to be unsafe by any official charged with protecting the public safety, upon order of such official.

   Any use for which a special exception is permitted as provided in Section 167.07 shall not be deemed a nonconforming use, but shall, without further action, be deemed a conforming use in such district.

   No nonconforming structure or use shall be maintained, renewed, changed or extended until a certificate of zoning compliance shall have been issued pursuant to Section 169.04 hereof.