(1)   The following lawful uses of land may be continued:

(a)   A use of land which existed prior to the effective date of this ordinance;

(b)   A use of land existing at the time of the annexation of such land to the city; or

(c)   A use of land existing at the time an amendment is made to the zoning ordinance of the city which changes such land to a more restricted district; although any such use does not conform to the provisions of this ordinance. However, if such nonconforming use, or another nonconforming use to which the land may be changed, is discontinued for a period of one year or more, then any future use of the property shall be only in accordance with the provisions of the zoning ordinance of the city.

(2)   The lawful use of a building located upon any land, except as provided in section 2302, may be continued although such use does not conform with the provisions of the zoning ordinance of the city and such use may be continued throughout the building if no structural alterations are made therein, except those required by law or ordinance. If no structural alterations are made in such building, a nonconforming use of the building may be changed to another nonconforming use of the same or more restricted use classification. The foregoing provisions shall also apply to any uses of buildings which may be made nonconforming by any subsequent amendment or change of the zoning ordinance of the city.

Nonconforming uses which may not be continued:

(1)   Whenever a nonconforming use of building has been changed to a more conforming use, such use shall not thereafter be changed to a less conforming use.

(2)   A building which has been damaged to the extent of more than 50 percent of its structural value by fire, explosion, natural cause, or the public enemy shall not be restored, except in accordance with all zoning regulations of the city. In the event of a question as to the structural value of such a building, the same shall be determined by three appraisers; one of whom shall be selected by the mayor, one of whom shall be selected by the owner of the building, and the third appraiser shall be selected by the two first so selected. If the first two appraisers so selected cannot agree on the selection of the third such appraiser, the judge of the appropriate court shall be requested to appoint such third appraiser. The decision of the appraisers, or a majority of them, shall be final and conclusive and shall be binding upon all concerned for the purpose of determining whether the damaged property may be restored. The cost of such appraisal shall be paid by the property owner.

(3)   The nonconforming use of a building or premises for the purposes of dismantling or wrecking automobiles or other vehicles of any kind, or for the purpose of storing junk, scrap iron and scrap material, including dismantled and wrecked automobiles or other vehicles, or other types of open storage, and which is located in other than “LI” Light Industrial District, shall be discontinued within five years from the effective date of this ordinance, and the buildings or premise thereafter devoted to a use permitted in the district in which such buildings or premises are located.

(4)   Where land is used for business signs, bulletin boards or billboards, at the time of passage of the zoning regulations, and are not in conformance with the zoning regulations, the use of such land for the business signs, bulletin boards or billboards shall be discontinued and the sign removed within five years after the effective date of the zoning ordinance. Land, as used in this paragraph, shall mean vacant land with signs on supports, as well as land occupied by buildings of structures with signs thereon.