Prior to landing the pilot intended to carry out an inspection of the flight strip for possible obstructions. The inspection was to be performed at 500 feet above ground level, with ten degrees of flap selected. During the inspection the aircraft suddenly began to "sink" rapidly. Thinking the engine had suffered a loss of power, the pilot selected full throttle and lowered full flap in preparation for an emergency landing. Although the engine accelerated to full power, the aircraft did not respond to other control imputs and it continued to descend until it was less than 30 feet above the ground. By the time the pilot had regained full control of the aircraft, it was on a collision course with the roof of a large building. The left main and nosewheel were torn off, and sheets of roofing iron were left hanging from the right mainwheel and left wing. The pilot was able to maintain control and manoeuvred the aircraft for a landing on the flight strip, using a windrow on the side of the strip to support the fuselage in place of the missing mainwheel. The pilot's description of the sequence of events and the lack of suitable terrain which could cause a significant down-draft, indicated that the aircraft probably stalled whilst the pilot was concentrating on the airstrip inspection. The pilot's inexperience caused him to mis-identify the cause of the "sink" and he used an incorrect stall recovery technique.