It is not treated. It is like the lumber we used for shelving years ago. I have a 12' 1x12 in the garage that I wanted to use for a shelf a couple of years ago. It is #1 or clear, but I think it is expensive. When I remodeled 25 years ago, I used 2x6 #1yp for strength on my rafters and 1x6 #1yp center match for decking. It would probably be cost prohibitive now. The last bumper hitch trailer I put a floor in, I used Brazilian iron wood for strength. Our semi trailers now have aluminum floors with apitong nailing strips. But apitong is not what it is cracked up to be. 40 years ago we used 2x8 yp center match in our trailers and moped them with linseed oil on a hot day. We got very good service out of them.
