If a nonconforming building or structure or a building or structure devoted to a nonconforming use is damaged by fire, flood, explosions, wind, earthquake, war, riot or other act, it may be restored and reconstructed provided that any such repair does not increase the degree of any nonconformance and further provided that such reconstruction shall be started within 12 months of such happenings. This term may be extended by the ZBA for insurance or other delays not caused by the owner.