Any lawful nonconforming use of land existing at the date of enactment of this subchapter may be continued, except that any nonconforming use or buildings may not be:
(A) Changed to another nonconforming use;
(B) Re-established after discontinuance for one year if it involves a substantial building; or after discontinuance for any period in other cases;
(C) Extended; or
(D) Rebuilt after damage exceeding 50% of its value.
(1988 Code, § 4.21-8)