Restoration. Any noncomplying building or structure or building or structure housing a nonconforming use which as a result of fire, explosion or other casualty has less than 50% of its existing floor area made unsafe and/or unusable may be restored, reconstructed or used as before, provided that the bulk, height and area requirements shall not be in excess of that which existed prior to said damage. Such restoration must be commenced within six calendar months and completed within two calendar years of such occurrence or the use of such building, structure or land as a legal nonconforming use shall thereafter be terminated. Abandonment shall only apply to nonconforming uses that were carried on in structures that are architecturally designed to be consistent with a permitted use.