A lawful nonconforming structure existing at
the time of the adoption or amendment of this chapter may be continued
although its size or location does not conform to the lot width, lot
area, yard, height, parking and loading, and access provisions of
this chapter. However, it shall not be extended, enlarged, reconstructed,
moved or structurally altered except when required to do so by law
or order or so as to comply with the provisions of this chapter.
Once a nonconforming use or structure has been
changed to conform, it shall not revert back to a nonconforming use
or structure. Once the Zoning Board of Appeals has permitted the substitution
of a more restrictive nonconforming use for an existing nonconforming
use, the substituted use shall lose its status as a legal nonconforming
use and become subject to all the conditions required by the Zoning
Board of Appeals.