After preflight, the pilot set the parking brake, primed the engine, and got out to hand-start the engine with the propeller. No one was on board to help hold the brakes. He turned the propeller, and the engine started. He entered the cabin, and placed his feet on the rudder pedals. The engine stopped, so he exited the airplane and hand-propped it again. The engine started and air from the propeller blew the entry door shut. The airplane started to move forward and he was not able to reenter the airplane to apply the brakes. The left wing collided with a hangar about 100 feet away, which spun the nose into the hangar. The left wing was pushed back into the fuselage, and both sustained substantial damage. The pilot said that he did not recheck the parking brake after placing his feet on the controls, and thought that the accident might have been prevented if he had gone back to step one of his hand-start checklist.