Whenever a nonconforming structure is destroyed by fire, or any other calamity, to the extent of 50 percent or less, the structure may be restored provided that restoration is started within one year and diligently pursued to completion. When the destruction exceeds 50 percent or the structure is voluntarily razed or is required by law to be razed, the structure shall not be restored except in full conformity with the property development standards for the zone in which it is located except that any residential structure(s), including multifamily may be reconstructed up to the original size, placement and density regardless of the extent to which it is damaged provided that restoration/reconstruction is started within one year and diligently pursued to completion.