Any use of property, existing at the time of the passage of this ordinance, that does not conform to the regulations prescribed in the preceding sections of this ordinance, shall be deemed a nonconforming use; except that any duplex or apartment use, existing at the time of the passage of this ordinance, shall be thereafter deemed a conforming use. Any lawful use, existing within a building at the time of the passage of this ordinance, in any business or industry, shall be deemed a conforming use upon the lot devoted to such use at the time of the passage of this ordinance.

The lawful use of land, existing at the time of the passage of this ordinance, although such does not conform to the provision hereon, may be continued; but, if such nonconforming use is discontinued, any future use of said premises shall be in conformity with the provisions of this ordinance.

The lawful use of the building at the time of the passage of this ordinance may be continued, although such does not conform to the provisions hereof, and such use may be extended throughout the building, provided no structural alterations, except those required by law or ordinance, are made therein. If no structural alterations are made, a nonconforming use of the building may be changed to another nonconforming use of the same or more restricted classification; provided, however, that in the event a nonconforming use of a building is once changed to a nonconforming use of a higher or more restricted classification, it shall not later revert to the former lower or less restricted classification.

The right of nonconforming use, to continue, shall be subject to such regulations as to maintenance of the premises and conditions of operation as may, in the judgment of the board of adjustment, be reasonably required for the protection of adjacent property.

In case of partial destruction by fire or other causes, not exceeding 50 percent of its value, the building inspector may issue permit for reconstruction. If greater than 50 percent and less than total, the board of adjustment may grant permit for repair, after public hearing and having due regard for the property rights of the persons affected, when considered in the light of the public welfare and in the character of the area surrounding the designated nonconforming use and the conservation and preservation of property.