Continuance of existing lawful use. Except as otherwise provided in this chapter, the lawful use of land or buildings existing at the date of the adoption of this chapter may be continued although such use or building does not conform to the regulations specified by this chapter for the zone in which such land or building is located; provided, however, that:

Discontinuance. In any district, whenever a nonconforming use of land, premises, building or structure, or any part or portion thereof, has been discontinued for a period of one year, such nonconforming use shall not thereafter be reestablished, and all future uses shall be in conformity with the provisions of this chapter. Such discontinuance of the active and continuous operation of such nonconforming use, or part or portion thereof, for such period of one year, is hereby construed and considered to be an abandonment of such nonconforming use, regardless of any reservation of an intent not to abandon the same or of an intent to resume active operations. If actual abandonment in fact is evidenced by the removal of buildings, structures, machinery, equipment and other evidences of such nonconforming use of the land and premises, the abandonment shall be construed and considered to be completed and all rights to reestablish or continue such nonconforming use shall thereupon terminate.

Three-year limitation on certain uses. Notwithstanding any other provisions of this chapter, any automobile wrecking yard or other junkyard and any billboard, advertising structure or nonconforming sign in existence in any agricultural or residential district at the date of enactment of this chapter shall, at the expiration of three years from such date, become a prohibited and unlawful use and shall be discontinued; provided, however, that lawfully existing signs accessory to a nonconforming business or industrial building shall not be subject to this subsection.

Restoration of damaged building. No nonconforming building damaged by fire or other causes to the extent of more than 75% of its assessed valuation shall be repaired or rebuilt except in conformity with the regulations of this chapter. Nothing in this chapter shall prevent the strengthening or restoring to a safe condition any wall, floor or roof which has been declared unsafe by the Code Enforcement Officer.

Extension. A nonconforming use shall not be extended, but the extension of a lawful use to any portion of a nonconforming building which existed prior to the enactment of this chapter shall not be deemed the extension of such nonconforming use.

Unsafe structures. Any structure or portion thereof declared unsafe by a proper authority, but not ordered to be demolished, may be restored to a safe condition.

Preexisting special uses. Those uses existing at the date of the adoption of this chapter which would otherwise be permitted only with a special use permit may be required to meet certain regulations as set forth in Article VI, Special Use Permits, for the particular use.

Alteration. A nonconforming building may not be reconstructed or structurally altered to an extent exceeding 50% of the assessed value of the building unless said building is changed to conform to the requirements of this chapter.

Changes. Once changed to a conforming use, no building or land shall be permitted to revert to a nonconforming use. A nonconforming use may be changed to a use of the same classification upon approval of the Board of Appeals or to a use of more restricted classification, and when so changed to a more restricted classification, such use thereafter shall not be changed to a less restricted classification.

Amendments. Whenever the boundaries of a district shall be changed so as to transfer an area from one district to another district of a different classification or whenever the text of this chapter shall be changed with respect to the uses permitted in a district, the foregoing provisions shall also apply to any nonconforming uses existing therein.