If a building or other structure containing a nonconforming use is damaged or destroyed by any means to the extent of fifty percent or more of its replacement value at that time, the building or other structure may be rebuilt or used thereafter only for a conforming use and in compliance with the regulations of the district in which the building or other structure is located. In the event the damage or destruction is less than fifty percent of its replacement value, based upon prevailing costs, the building may be restored to its original condition and the occupancy or use of such building which existed at the time of such partial destruction may be continued. In either event, restoration or repair of the building or other structure must be started within a period of one year and diligently prosecuted to completion.