The pilot was flying the helicopter to the fuel pumps on the airport and made a high approach due to other aircraft traffic. About 50 feet above the ground he experienced "settling with power". He could not arrest the descent and the helicopter impacted the ground, bounced, became airborne again, and was spinning due to the separation of the tail boom and tail rotor. The helicopter then struck a hangar and impacted the ground a second time. The pilot reported that there were no pre-impact mechanical deficiencies with the helicopter. The helicopter had about 16 hours since a complete rebuild, and less than one hour since annual inspection.