Within the zones established by this chapter or amendments that may later be adopted, there exist lots, structures and uses of land and structures which were lawful before this chapter was passed or amended, but which would be prohibited, regulated or restricted under the terms of this chapter or future amendments.

To avoid undue hardship, nothing in this chapter shall be deemed to require a 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 this chapter 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 work shall be diligently carried on until completion of the building involved.

Uses, lots and structures existing, except nonconforming signs, lawfully prior to the effective date of this chapter which, by reason of this chapter are no longer conforming, shall be considered as legally nonconforming and shall be subject to provision of this article.

Uses, lots and structures existing unlawfully prior to the effective date of this chapter and which remain unlawful shall be considered illegal and, unless remedial action is taken (e.g., brought into conformance by an another acceptable zoning device permitted by this chapter), shall be prosecuted as a zoning violation in accordance with this chapter.

Uses, lots and structures existing lawfully or unlawfully prior to the effective date of this chapter which are made lawful as a result of the provisions of this chapter shall be considered as conforming.

A nonconforming use which has been discontinued or abandoned for six consecutive months or for 18 months during any three-year period shall not again be used for a nonconforming use.

In the event that 50% or less of the replacement value of a building used for a nonconforming use is damaged or destroyed or removed by fire, flood, explosion, war, riot or act of God, it may be reconstructed within six months after such happening and may be used for the original nonconforming use or a new conforming use.

A nonconforming use may be changed to a conforming use. If no structural alterations are made, any nonconforming use of a structure or structure and premises may, as a special exception, be changed to another nonconforming use, provided that the Board of Appeals finds that the proposed use is equally appropriate or more appropriate to the district than the existing nonconforming use.

A nonconforming use occupying only a portion of a property as of September 8,1987, shall not be permitted to make any expansion, except as follows:

A nonconforming lot which existed and was in use prior to September 8,1987, shall be permitted to be occupied continuously for the same use or for a new conforming use.

A nonconforming lot which was unimproved as of September 8,1987, shall hereinafter only be used when permission is granted by the Board of Appeals except as follows:

No nonconforming use or nonconforming lot shall be renewed, changed or extended until a certificate of zoning compliance shall have been issued by the Code Enforcement Officer. The certificate of zoning compliance shall state specifically wherein the nonconforming use or lot differs from the provisions of this chapter.