What are your plans for finishing out the rest of the building?? Ceiling, insulation, full open 30x40 area or divided down with a smaller room somewhere??
My 30x40x12 was built by the previous owner. His only intended use was storage area, plus a 16x30 woodworking shop in the back of the building.
He built his 16' room with an 8ft ceiling by building a loft floor. A 2x6" wall runs across the building, on top of which he built a deck with 2x12s, which ended up 18-20 below the bottom chord of the trusses.
So here is what I have:
The stairs lead to the 16x30 deck. Other than having to climb through the truss at the top of the stairs, and another 8' behind that, it is all open area.
Now that I have concrete in the remaining 24x30, plans are to put in ceiling and insulation in that area and a short stub wall to seal off the deck area. I may put in higed or removeable panels in teh gap between the deck and the bottom of the truss in order to allow long items to be slid up on the deck area.
Ideal, and the way I would have doen startng from scratch?? No, but it there and it's very useable, so I'll go with it. I like the seperated heated space, works well for my uses.
What you do will depend on your intended uses, and how big a deck area you need.
Something my Dad did in his pole building was to build a small deck over his workbench area. Only about 8' wide and 7' off the floor, which would give you 5'ish below the ceiling. Not somewhere you would want to work every day, but for storage it works fine.