I put up a 30' x 40' all steel shop. It has two 10' roll up doors and a walk in. I have a two post 4 point Bend Pack lift that has 7' of clearance under it when raised and will hold 9000 lbs. It is 15.5' at the peak and 12.5" at the edges. I used all steel due to living in Florida. There are 2 types of people, those who have termites and those who do not know they have termites. I used double 4" tubes to span the building from floor to roof to floor and welded them all. I also used galvanized bottoms all of the way around the building so that I could wash out the building and not have to worry about the base rusting. It has stood for 15 years with no problems except one. I eventually found that I didn't have enough room and added a second floor on about 1/4 of the building to give me storage up above that I can still stand in. My advice would be to at least insulate the roof.
