The lawful use of buildings existing at the time of adoption of this chapter or an amendment thereto or of a change in the district classification may be continued even though such use does not conform to the provisions hereof. If no structural alterations are made, a nonconforming use of a building may be changed to another nonconforming use of the same or more restricted classification, but whenever a nonconforming use is changed to a more restricted use or to a conforming use, it shall not thereafter be changed to a less restricted use.

The nonconforming use of a building may be extended throughout those parts thereof which were manifestly arranged or designed therefore prior to adoption of this chapter or an amendment thereto.

No building which has been damaged by fire, explosion, act of God or the public enemy to the extent of more than 60% of its reproduction value shall be restored except in conformity with the district regulations.

In the event that the nonconforming use of a building or premises in a district is discontinued for a period of six months or more, such building or premises shall thereafter be used only in conformity with the regulations of the district in which it is located, regardless of change in ownership of the property.

The casual, intermittent, temporary, or illegal use of land or buildings shall not be sufficient to establish the existence of nonconforming use and the existence of a nonconforming use on a part of a lot or tract shall not be construed to establish the nonconforming use on the entire lot or tract.