Except as otherwise provided herein, any lawfully established use of a building or land existing at the time of the enactment of this chapter or amendments thereto may be continued although such use does not conform with the provisions of this chapter.
A. 
Whenever any part of a building, structure or land occupied by a nonconforming use is changed to or replaced by a use conforming to the provisions of this chapter, such premises shall not thereafter be used or occupied by a nonconforming use.
B. 
Whenever a nonconforming use of a building or structure has been discontinued, as evidenced by vacancy, for a period of six consecutive months, or whenever there is evident a clear intent on the part of the owner to abandon a nonconforming use, such use shall not after being discontinued or abandoned be reestablished and the use of premises thereafter shall be in conformity with the regulations of the district.
C. 
Where no enclosed building is involved, voluntary discontinuance of a nonconforming use for a period of three months shall constitute abandonment, and shall not thereafter be used in a nonconforming manner.
The nonconforming use of any building, structure or portion thereof may be changed, with the approval of the Board of Appeals, to a use of a more restricted classification, and when so changed shall not thereafter be changed to a less restricted classification.
Normal maintenance of a nonconforming building is permitted. However, such building may not be reconstructed or structurally altered during its life to an extent exceeding in aggregate cost 25% of the market value of the building unless changed to a conforming use.
A nonconforming use shall not be extended, but the extension of a lawful use to any portion of a nonconforming building designed or manifestly arranged for such use, which existed prior to the enactment of this chapter, shall not be deemed the extension of such nonconforming use.
No building damaged by fire or other causes to the extent of more than 60% of its real value, as computed through the use of equalization rates current at the time, shall be repaired or rebuilt except in conformity with the regulations of this chapter.
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, the foregoing provisions shall also apply to any nonconforming uses existing therein.