Any nonconforming use or structure existing at the time of the passage of this chapter may be continued upon the lot or in the building so occupied, and any such structure may be restored or repaired in the event of destruction thereof by fire, explosion, act of God or act of a public enemy after the passage of this chapter, provided that such restoration or repairs shall be made within one year from the date of destruction. Nothing in this chapter shall prevent the strengthening or restoring to a safe condition of a wall declared unsafe by the Building Inspector or Construction Code Official or any other official so designated by the Mayor and Council.

No nonconforming use shall, if once changed into a conforming use, be changed back again into a nonconforming use.

The cost of structural alterations made in such building shall in no case exceed 50% of its value, nor shall the building be enlarged unless the use thereof is changed to a conforming use.

No nonconforming use shall be extended so as to diminish the extent of a conforming use.