When I was asked to built a manger for the front lawn of our church one of the things that I had to consider while building it was making it look like it was 2000 years old.
A local lumberyard that specializes in lumber for shipping pallets provided the rough-sawn lumber, which gave me the old look I was after.
I had to make it strong and as light as possible. To accomplish this, I made the frame out of 2×2s and used ½ x 6 and ½ x 4 boards for the siding.
Because the lumber was not very dry, I ran into some problems when the panels that did not have an outside frame warped. You can see what happened to the first set of roof panels. I made the second set out of ½ x 6-inch Cedar fence boards and they worked fine.
Some additional construction considerations were that I had to build it so it could be assembled and disassembled easily. since it is stored for eleven months of the year, it had to take up as little room as possible. The entire manger consists of ten panels that bolt together using 4-inch long, ¼-inch carriage bolts, which can be assembled in about a half hour. Once disassembled and stored, it takes up nine feet of garage wall space, eighteen inches deep.