The following provisions shall apply to all buildings and uses existing on the effective date of this chapter, to all buildings and uses that may become nonconforming or noncomplying by reason of any subsequent amendment to this chapter and the Land Use District Map, and to all complying buildings housing nonconforming uses:
Any lawful nonconforming use of buildings or open land in existence on the effective date of this chapter may be continued indefinitely, provided that it:
A. 
Shall not be enlarged, altered, extended, reconstructed or restored, except as provided in this chapter, or placed on a different portion of the lot or parcel of land occupied by such use on the effective date of the chapter, nor shall any external evidence of such use be substantially increased by any means;
B. 
Shall not be moved to another location where such use would be nonconforming;
C. 
Shall not be changed to another nonconforming use without prior approval by the Zoning Board of Appeals, and then only to a use which, in the opinion of the Zoning Board of Appeals, is of the same or a more restricted nature;
A. 
Normal repair and maintenance of or structural alteration within a noncomplying structure shall be permitted, provided that such action does not increase the degree of or create any new nonconformity.
B. 
Any noncomplying structure declared unsafe by the Building Inspector shall be restored to a safe condition within a time period provided for such restoration by the Building Inspector.
C. 
A lawful use may be extended to any portion of a noncomplying structure that existed prior to the enactment of this chapter. However, no nonconforming use shall be extended to displace a conforming use.
Nothing contained in this chapter shall be deemed to prevent the restoration of a lawful, nonconforming use after damage for any reason or by any cause, provided that the bulk, height, and area shall not be in excess of that which existed prior to the damage, and provided further that the restoration is commenced within six months after the damage and completed within two years of such occurrence.