We're putting on a green roof right now. I put really thin, really cheap from the guy down the road, blue board on the plywood. The plywood is over 12" centered 2x12's. On top of the insulation is the EPDM. I've put in one sun tube and have one to go. The EPDM is currently laying on the roof with no glue or nails at all. The seems have 2x12's with concrete blocks on them holding them down. The EPDM is in 10 foot widths. We've got 3 37' lengths up there. So far, after several rains with wind, there are no leaks at all. I'm impressed with the EPDM. Its stout! We've got Enkadrain to go on next. On the Enkadrain we're gonna put down flakes of straw bales. 4" thick flakes maybe. We'll keep adding straw and manure and whatnot for a while until it gets to be around 3-4 inches of growing medium. Hope it works.