Notwithstanding anything to the contrary hereinabove set forth, nothing in this chapter shall prevent the reconstruction, repairing, rebuilding and continued use of any nonconforming building or structure damaged or destroyed by fire, explosion, flood, windstorm or other act of God; provided, however, that there shall be no enlargement of the original structure and that the work shall be initiated within six months from the occurrence of such damage or destruction and shall be diligently pursued to completion.