What are the solutions to stain lumber for outdoor use, except buying pressure-treated wood? What I want to do is take the old lumber, which is still in good shape, but turned gray because of the weather/rain/etc, sand it, and then stain and re-use for decking. What are those stains/paints/etc. called? So I assume there is something I could stain boards with that would prevent it from rot, mould etc.