On August 21, 1995, at 0940 central daylight time, an Enstrom 280C, N911BT, was substantially damaged upon collision with a hangar while hover taxiing near Houston, Texas. The flight instructor and the instrument rated private pilot receiving instruction were not injured. The instructional flight was conducted under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the local flight for which no flight plan was filed. The owner of the helicopter was not rotorcraft rated, and had been receiving dual instruction in his helicopter since July 22, 1995, with 9.1 hours of dual instruction being logged in the helicopter at the time of the accident. According to the owner, the instructional flight was conducted with both doors removed from the helicopter. Following the last landing the owner hovered the helicopter to a concrete pad in front of his hangar. After landing the helicopter he reached for the checklist to execute a normal shutdown. A moderate rain was falling, and the flight instructor told the pilot "not to shutdown the engine and he would taxi it into the hangar." The owner reports he responded to the flight instructor no. The owner further reported that he told the flight instructor that "it would only take him a minute to go get the doors and put them on." The flight instructor said "it was not a problem" and took the controls and brought the helicopter to a low hover. The flight instructor made a 90 degree pedal turn to the left and slowly began to approach the hangar while hovering with the skids just above the ground. The owner further stated that the helicopter was inside the hangar when he felt a slight updraft and the main rotor system impacted the top structure of the hangar destroying all three main rotor blades. The hangar sustained substantial damage, and the owner's automobile, which was parked inside the hangar, was also damaged by flying debris from the helicopter. The flight instructor did not complete the Pilot/Operator Report (NTSB Forms 6120.1/2) provided to him by the investigator-in- charge.