If a lawful use involving individual structures, or of a structure and premises in combination, exists at the effective date of amendment of this Zoning Regulation that would not be allowed in the district under the terms of this Zoning Regulation, the lawful use may be continued so long as it remains otherwise lawful, but shall be subject to the following provisions:
   (a)   Enlargement or Alteration of Structure:  No existing structure devoted to a use not permitted by this Zoning Regulation in the district in which it is located shall be enlarged, extended, constructed, reconstructed, moved or structurally altered except in changing the use of the structure to a use permitted in the district in which it is located.
   (b)   Extension of Use Throughout Building:  Any non-conforming use may be extended throughout any parts of a building which were manifestly arranged or designed for such at the time of amendment of this Zoning Regulation, but no such use shall be extended to occupy any land outside such building.
   (c)   Change of Non-Conforming Use: If no structural alterations are made any non- conforming use of a structure, or structure and premises, may be changed as a conditional use, in accordance with  this chapter and  to another non-conforming use provided that the Board of Zoning Appeals shall find that the proposed use is equally appropriate or more appropriate to the district than the existing non- conforming use. In permitting such change, the Board of Zoning Appeals may require appropriate conditions and safeguards in accordance with other provisions of this Zoning Regulation.
   (d)   Permitted Use May Not Revert to Non-Conforming Use: Any structure, or structure and land in combination, or land on which a non-conforming use exists in conformance with the regulations for the district, may not revert to a non- conforming status.
   (e)   Discontinuance: When a non-conforming use of a structure or structure and premises in combination is voluntarily discontinued or abandoned for more than two (2) years (except when government action impedes access to the premises), the structure or structure or premises in combination, shall not thereafter be used except in conformity with the regulations of the district in which it is located.
   (f)   Removal or Destruction of Structure: When non-conforming use status applies to a structure and premises in combination, removalor destruction of the structure shall eliminate the non-conforming status of the land.