A nonconforming status shall exist when a use or structure which does not conform to the regulations prescribed in the district in which such use or structure is located was in existence and lawfully operating prior to the adoption of the ordinance from which this chapter is derived.

No nonconforming use or structure may be expanded or increased except to provide off-street loading or off-street parking upon approval of the city council.

Repairs and normal maintenance may be made to a nonconforming building provided that no structural alterations or extensions shall be made except those required by law or ordinance, unless the building is changed to a conforming use.

Any nonconforming use may be changed to a conforming use and once such change is made, the use shall not thereafter be changed back to a nonconforming use.

Whenever a nonconforming use is abandoned, all nonconforming rights shall cease and the use of the premises shall thenceforth be in conformity with this article. Abandonment shall involve the intent of the user or owner to discontinue a nonconforming operation and the actual act of discontinuance. Discontinuance of a business or the vacancy of a building or premises occupied by a nonconforming use for a period of six months shall be construed as conclusive proof of intent to abandon the nonconforming use. Any nonconforming use not involving a permanent type of structure which is moved from the premises shall be considered to have been abandoned.

If a nonconforming structure or a structure occupied by a nonconforming use is destroyed by fire, act of God or other cause, it may not be rebuilt except in conformance to the provisions of this article, unless permitted by the zoning board of adjustment, taking into consideration the property owner's circumstances and the effect on surrounding properties, after a public hearing with notice provided in accordance with section 42-82(c) [42-95(c)] for appeals before the zoning board of adjustment. The zoning board of adjustment may provide restrictions on such rebuilding. Such nonconforming use or structure may be rebuilt without such permission if such destruction does not exceed 50 percent of its reasonable value so long as permits for such rebuilding are obtained within six months of such destruction, and the size and function of the nonconforming use are not expanded.

Notwithstanding any of the provisions of this article, a nonconforming HUD-code manufactured home may be exchanged or replaced by another HUD-code manufactured home, provided the newly located residential unit is owner-occupied.