I'm making a small building 7x3m and 3m high, I have 50mm box steel frame at 1220 centers so I can just stick shuttering ply to the outside and the inside, 50mm insulation in between for a fast build. Do you think I need to put a foam type gasket in between the ply and steel for rot or anything similar? Or use house wrap and vapour barrier on the outside/inside? I am intending on living in the building. Just wondered if any of you have any experience or advice for this build, do you think it's structurally sound enough just doing 3m uprights for each join of ply?