Any lawful nonconforming use which existed on the date of adoption of this chapter may be continued, and any existing structure designed, arranged, intended or devoted to a nonconforming use may be structurally altered, subject to the following regulations:
A. 
A nonconforming use shall not be enlarged unless the use is changed to a conforming use; provided, however, that, where a building meets the use requirements of this chapter and is nonconforming because of height, area and/or yard regulations, said use may be enlarged, provided that the height, area or yard regulations are not further violated.
B. 
A nonconforming use changed to a conforming use shall not thereafter be changed back to a nonconforming use.
C. 
A nonconforming use in existence at the time of adoption of this chapter shall not be permitted to be changed to another nonconforming use.
D. 
In the event that there is a cessation of operation of any nonconforming use for a period of 24 consecutive calendar months, the same shall be prima facie evidence of an abandonment of the use. Any subsequent exercise of such abandoned nonconforming use shall be deemed a violation of the terms of this chapter.
Nothing in this chapter shall require any change in plans, construction or designated use of a structure for which a building permit has been issued when construction has been diligently prosecuted within six months following the date of such permit and completed within the terms of such permit.
Any nonconforming use or structure existing at the time of adoption of this chapter may be continued upon the lot or in the building so occupied or any structure may be restored or repaired within one year in the event of partial destruction thereof. In the event that reconstruction is not commenced within such period, then the entire structure shall be razed by the owner.
Nothing in this chapter shall be interpreted as implied authorization for or approval of the continuance of the use of a structure or premises in violation of zoning regulations in effect at the time of adoption of this chapter.
The foregoing provisions of this Article shall also apply to structures, land or uses which hereafter become nonconforming due to any reclassification of zones under this chapter or any subsequent change in the regulations of this chapter.