The pilot of the amphibious airplane reported that while on final approach to runway 26 he had trouble viewing the runway due to glare from the setting sun. He recalled making “...continuous efforts to block the sun glare.” He planned to make a gradual descent on the final approach to get the best forward view and peripheral views of the area. While descending, he further described that “the brightness inside the cockpit was difficult to observe instruments. I descended towards what I was convinced was the runway. I remember nothing else from that time forward.” The airplane subsequently struck the roof of a business, and the wreckage came to rest next to the building in the parking lot. The airplane’s fuselage, both wings, empennage, and floats were substantially damaged. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. Based on this information, the airplane likely struck the building after the pilot allowed the airplane to descend too low on the approach to the runway.