I don't know if it will be possible to access this link, but it is so cool that I'll post it in the hope that it will work.... Llama shelter made from stock panels!

In case the link does not work, it is a llama (alpaca!) shelter made by arching cattle panels, stabilizing them in that position with T posts, and using zip ties to secure a tarp to the exterior. The arch/tunnel is open on both ends for ventilation, which is critically important. You do not want a barn to be all sealed up tightly.

I don't want to use a tarp. Thinking...what else would work for a roof? Join and arch metal roofing over the stock panel?