Restoration of a Building or Structure. Any nonconforming building or structure, damaged or destroyed by fire or other casualty, may be repaired, reconstructed and used as before, provided that the volume of such use, building, or structure shall not exceed the volume that existed prior to the damage, destruction, or casualty by more than 25%, is allowed one time only, and provided, that any nonconformities, such as setbacks, are not further enlarged.