The lawful use of a building existing upon the date this Chapter is adopted may be continued, although such use does not conform with the provisions of this Chapter, and such use may be extended throughout the building; providing that no structural alterations, except those required by law or ordinance, are made therein. If no structural alterations are made, a non-conforming use of a building may be changed to another non-conforming use of the same or more restricted classification. The foregoing provisions shall also apply to non-conforming uses in districts hereafter changed. Whenever a non-conforming use of a building has been changed to a more restricted use or to a conforming use, such use shall not thereafter be changed to a less restricted use.

No building which has been damaged by fire, explosion, act of God or the public enemy, to the extent of more than fifty percent (50%) of its structure, shall be restored except in conformity with the regulations of this Chapter. The remnants of any damaged building not to be restored shall be removed within one hundred eighty (180) days.

No building or portion thereof used in whole or in part for a non-conforming use in a dwelling district which remains idle or unused for a continuous period of one hundred eighty (180) days, regardless of ownership, whether or not the equipment or fixtures are removed shall again be used except in conformity with the use regulations of the district in which such building is located.

No existing building or premises devoted to a use not permitted by this Chapter in the district in which such building or premises is located, except when required to do so by law or ordinance, shall be enlarged, extended, reconstructed or structurally altered, unless such use is changed to one permitted in the district in which such building or premises is located.