I guess I'm redesigning my shop/house out of I-beams now. Need support posts for the greenhouse structure anyway so gonna make them 6" I-beams instead of 4" square tubing. Might be cheaper posts actually and just need to weld fancy flanges to them before hot dipping so I can eventually build 2-3 story rooms randomly in them as I need rooms. My dad has a pile of galvanized stair treadplates too so I can make all kinds of really nice stairs cheap. Since I can easily go 2 stories tall with roof gardens now I might make the initial outer greenhouse dimensions smaller so I don't bite off more than I can chew in one year.