premise: What supplies are needed to build a treeless tree house?
hypothesis: Six cement blocks (I HIGHLY recommend the kind with epoxied-in metal post brackets. Although they are more pricey, they are much more secure and allow for easily adjusting post and block assemblies. More on that as we go along.)        Six 8-foot pressure treated 4x4 posts        Six 8-foot pressure treated 2x6 boards        One 4- by 8-foot 3/4" board OSB (same dimensions in exterior grade plywood is another option)        Approximately twenty 8-foot 2x4 boards        Four 10-foot 2x4 boards        Five 26" x 8' corrugated plastic roof panels        One box (50 pcs.) of roofing screws for corrugated panels (the kind with built-in rubber washers)        5 lb. box of 3" exterior grade screws        5 lb. box of 1 5/8" exterior grade screws        Two 50 lb. bags of general purpose sand        Gallon of waterproof sealer        Gallon of deck restoring paint