I have been trying to find a way to make corrugated metal roofing and I have come up with a good way. In Walmart, in the craft section, you will find packages of 1/8" dowels. They are 6" long and come 50 to the package. Cost is about $1.50. I cut the 6" dowels in half and lay them side-by-side onto a piece of tape to hold them tightly together. I then glue a piece of wood or plywood about 3"x6" to the wood dowels. Let the glue dry well. After an hour or two, remove the tape from the dowels. Take aluminum foil, shiny side down and place it on top of the dowels. Holding on to one end of the foil, press down on the foil with a soft eraser. This will emboss a corrugated pattern on to the foil. It is now ready to be glued to roofs of houses and sheds. It can also be used as metal siding on factory buildings. Use heavy duty aluminum foil, not the ordinary kitchen wrap.

I found another way. Just take corrugated cardboard and peel off one outside layer and then using a sandpaper block, carefully smooth out the surface. It's to large for HO scale, but could be used for O scale and larger. I found some very thin corrugated stock that I think may work for HO scale, but I don't have any at the moment.