The lawful use of any building or lot existing on the effective date of this chapter may be continued even if the use and/or the building does not conform to the regulations of the district in which such premises are located, and such buildings or uses shall be deemed nonconforming. The effective date of this chapter shall also include the effective date of any subsequent amendment to this chapter which may cause any use or building to become a nonconforming use or building, subject to the regulations herein. Any use which is permitted in a district by a special use permit and has received approval from the Planning Board shall be deemed a conforming use.
Normal maintenance and repair of, and incidental alteration of, a nonconforming building or a building occupied by a nonconforming use is permitted if it does not create any new nonconformity in the building or extend the nonconforming use. No major structural alteration, restoration or enlargement shall be made in a building occupied by a nonconforming use, except:
A. 
When required by law.
B. 
To adapt the building to a conforming use. A nonconforming building that is, or is to be, devoted to a conforming use may be reconstructed, structurally altered, restored or repaired, in whole or in part, provided that such action does not increase the degree of nonconformity.
A. 
If a nonconforming use or building or other structure of nonconforming bulk sustains an amount of damage or destruction by any cause, which amount is officially appraised to be 55% or more of its assessed value, the building or other structure or tract of land shall thereafter be occupied and used only in conformity with the provisions of this chapter.
B. 
If a nonconforming building, structure or use is damaged to an extent less than 55% of its assessed value, such building, structure or use may be restored, but not beyond the limits of the previous nonconformity or to increase the intensity or degree of the nonconforming use.
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 effective date of this chapter shall not be deemed the extension of a nonconforming use. A nonconforming use shall not be moved to any portion of the building, structure or land not so occupied on the effective date of this chapter.
Any nonconforming use may be changed to a conforming use. Once changed to a conforming use, no building or land shall revert to a nonconforming use. On application to and with the approval of the Zoning Board of Appeals, a nonconforming use may be changed to any other nonconforming use which the Zoning Board of Appeals deems to be in keeping with the uses permitted in the district in which the said nonconforming use is located.
If active and continuous operation of a nonconforming use is not carried on during a continuous period of one year for a building or six months if such use occupies land wherein there is no consequential structure devoted to such use, the nonconforming use shall be deemed to be discontinued, and the building or land where such nonconforming use previously existed shall thereafter be occupied and used only for a conforming use. Intent to resume active operations shall not affect the foregoing. For purposes of this chapter, it shall make no difference whether discontinuance of operations is voluntary or involuntary.
Notwithstanding any other provisions of this chapter, any automobile-wrecking yard or other junkyard in existence in any district at the date of enactment of this chapter shall, at the expiration of two years from such date, become a prohibited and unlawful use and shall be discontinued.