The lawfully existing nonconforming use of all or part of a building, structure or parcel may be continued subject to the following provisions:
A. The nonconforming use of part of a building, structure or parcel shall not be expanded or extended into any other portion of such building, structure or parcel.
B. If a nonconforming use of a building, structure or parcel is discontinued for a period of ninety (90) days, it shall not be renewed.
C. A nonconforming use shall not be changed to another nonconforming use. (1965 Code title 6 § 501.9)