The airplane was damaged when it landed on the un-paved portion of a runway under construction and struck the end of the existing runway. All three landing gear were separated from the airplane. In a written statement, the pilot stated that he landed on the un-finished portion of a runway extension that was approximately 8 inches lower than the existing runway. He stated that there were no markings visible from the air to indicate that the extension was not useable. Plywood chevrons were placed in the grass adjacent to the sides of the runway extension. There were no markings on the new runway extension. The runway extension project was listed in a notice to airmen (NOTAM). This report is based on information received by the NTSB. Additional details may be found in the NTSB’s public docket for this case. For further information, please contact the NTSB Office of Public Inquiries.