Nonstandard uses existing immediately prior to the effective date of this chapter may be continued, although such uses do not conform to the provisions hereof. Nonstandard buildings or structures may be enlarged or extended, converted, reconstructed, or structurally altered as follows:
(A) Enlargements, extensions, conversions, or structural alterations may be made as required by law or ordinance.
(B) Structural alteration of buildings or structures may otherwise be made if such changes do not encroach into an existing front yard, side yard, or rear yard which is less than the minimum required yards for the district in which they are located.
(C) Enlargement, extension, conversion of buildings or structures may otherwise be made if such changes comply with the minimum required yards, lot area, height, landscaping, parking, and density for the district in which they are located.