Any nonconforming use, premises or structures situated appurtenant thereon, or one or more of a group of nonconforming premises, uses or structures situated thereon related to one industry but under one ownership, which has been or may be destroyed by fire, flood, explosion, earthquake, war, riot or other act of God, may be reconstructed and used as before, if it is done within twelve months of such disaster and if the restored use does not exceed the square foot area as it existed at the time of such disaster.