The pilot reported that he was departing an airport near a ridge. Everything was normal on takeoff; however, during climbout shortly after departure, the airplane descended as if it was in a strong downdraft and he could not maintain altitude. The passenger, who was a glider pilot, stated that he estimated the airplane was approximately 200 feet above the ground when the pilot reported that they were losing altitude. Witnesses at the airport stated that during takeoff roll, the airplane rotated nose-up about one-third to one-half down the 3,088-foot long runway. The airplane remained in that attitude down the entire runway, about 20 feet above the ground. The airplane pitched up further, just cleared trees off the departure end of the runway, then appeared to stall and descend behind the treeline. The airplane subsequently impacted the front yard of a residence off the departure end of the runway and came to rest upright. Examination of the airplane by a Federal Aviation Administration inspector revealed that during the impact, all three landing gear separated. Additionally, the firewall and lower fuselage were substantially damaged. The pilot reported no preimpact mechanical malfunctions with the airplane and the inspector did not observe any. The recorded wind at an airport approximately 10 miles from the accident site, about 25 minutes after the accident, was variable at 5 knots. The recorded temperature at that time was 84 degrees F.