Maintenance and repair shall be required of every nonconforming building or structure and of every building or structure occupied, in whole or in part, by a nonconforming use, as set forth in the Codified Ordinances of the City of South Euclid. A building or structure occupied by a nonconforming use shall not be altered, except in accordance with the following provisions:
(a) A structural alteration of a building or structure containing a nonconforming use shall not be made, unless:
(1) Such alteration is required by some provision of the Codified Ordinances of the City of South Euclid;
(2) Such alteration is made pursuant to the provisions controlling expansion or enlargement;
(3) The purpose of the alteration is to convert the building or structure to a conforming use; or
(4) The purpose of the alteration is to comply with applicable regulations of this Planning and Zoning Code.
(b) A nonconforming residential use located within a Manufacturing or Commercial District may be structurally altered or repaired in any manner to improve interior livability, provided that no such improvement shall be permitted if it would result in an increase in the number of dwelling units or exceed the area, yard or height provisions of Chapters 726 and 727.