Continuance. Except as otherwise provided in this chapter, the lawful use of land or buildings existing at the date of the adoption of this chapter may be continued, although such use or building does not conform to the regulations specified by this chapter for the zone in which such land or building is located; provided, however:

Abandonment. A nonconforming use shall be presumed to be abandoned when there occurs a cessation of such use or activity by an apparent act or failure to act on the part of the tenant or owner to reinstate such use within a period of six months from the date of cessation or discontinuance. Such use shall not thereafter be reinstated and the structure shall not be reoccupied except in conformance with this chapter.

Restoration. If any nonconforming building is destroyed by reason of windstorm, fire, explosion or other act of God or the public enemy to any extent of more than 50% of the physical structure as determined by the Construction Code Official, then such destruction shall be deemed complete destruction, and the structure may not be rebuilt, restored or repaired except in conformity with the regulations of this chapter. Nothing in this chapter shall prevent the strengthening or restoring to a safe condition of any wall, floor or roof which has been declared unsafe by the Construction Code Official.

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

Alterations. A nonconforming building may not be altered so as to increase in any manner the degree of nonconformance.

Construction approved prior to chapter. Nothing herein contained shall require any change in plans, construction or designated use of a building for which a building permit has been heretofore issued prior to the date of the adoption of this chapter.

District changes. Whenever the boundaries of a zone shall be changed so as to transfer an area from one zoning district to another zone of a different classification, the foregoing provisions shall also apply to any nonconforming use existing therein or created thereby.

Nonconforming signs. In cases where a portable or protruding sign of permanent materials or a sign structurally part of a building shall be destroyed or required because of a change of sign, the replacement shall conform to the provisions of this chapter.