here's a link to the plans I used to build my smokehouse. I used cedar tongueand groove siding, purchased at Lowes. The racks are expanded stainless. Kind of pricey, but if you use galvanized, be ready to be very sick.[:'(]
My total cost was right around $200. Well worth it. Works like a dream.

http://www.canr.uconn.edu/ansci/ext/build_smokehouse.pdf