No such structure may be enlarged or altered in a way which increases its nonconformity.

Any such structure may be restored or repaired in the event of partial destruction or deterioration. Where the foundation of the structure is left remaining, the structure shall be considered partially destroyed and the nonconforming structure may be rebuilt and used for the same purpose as before, provided that it does not exceed the height, area and bulk of the original structure. In the event that the structure, including the foundation, is destroyed, the entire structure shall be considered destroyed and may be rebuilt to the original specifications only upon approval of a use variance as provided by State statutes.