Where a lawful structure exists on the effective date of adoption or amendment of this chapter that could not be built under the terms of this chapter by reason of restrictions on area, lot coverage, height, yards, its location on the lot, or other requirements concerning the structure, such structure may be continued so long as it remains otherwise lawful, subject to the following provisions:

1.   No such nonconforming structure may be enlarged or altered in such a way which increases its nonconformity, but any structure or portion thereof may be altered to decrease its nonconformity.

2.   Should such nonconforming structure or nonconforming portion of structure be destroyed by any means to an extent of more than 50 percent of its replacement cost at time of destruction, it shall not be reconstructed except in conformity with the provisions of this chapter.

3.   Should such structure be moved for any reason for any distance whatever, it shall thereafter conform to the regulations for the district in which it is located after it is moved.