If anyone is interested: here is an image of my kiln shed.
It has two I-beams (from Benco Steel in Hickory) and then Bar Joists like you see in industrial buildings like Lowes or Walmart. I got them from Roger at Grassy Creek Hardware but think he got them from ABS (American Building Systems in Johnson City TN)
Those are welded together and then Hat Channel (from Roger) and then the 5-V metal roof (Roger) is screwed down.
It will make you feel better!