A. 
A nonconforming use is the lawful use of a building or premises existing at the time of the adoption or amendment of a zoning ordinance which may be continued although such use does not conform with the provisions of this chapter. Such nonconforming use may not be extended. The total structural repairs or alterations in such a nonconforming building shall not during its life exceed 50% of the assessed value of the building unless permanently changed to a conforming use. If such nonconforming use is discontinued for a period of 12 months, any future use of the building and premises shall conform to the ordinance.
A lawful nonconforming structure existing at the time of the adoption or amendment of this chapter may be continued although its size or location does not conform to the frontage, width, height, area, yard, parking, loading, access or distance requirements of this chapter. However, it shall not be extended, enlarged, reconstructed, moved or structurally altered except when required to do so by law or order or so as to comply with the provisions of this chapter.
Once a nonconforming use or structure has been changed to conform, it shall not revert back to a nonconforming use or structure. Once the Zoning Board of Appeals has permitted the substitution of a different nonconforming use for an existing nonconforming use, the substituted use shall lose its status as a legal nonconforming use and become subject to all the conditions required by the Zoning Board of Appeals.