Pressure Treated Doug Fir
If economy and longevity are your bag, go with pressure-treated wood. It’s stainable, hard enough to resist abuse, and many brands carry a lifetime (though limited) warranty. But beware, pressure-treated lumber is not rot and insect resistant, however it's cheaper than redwood or cedar. But inexpensive treated wood is often full of moisture and will shrink unevenly and twist when it dries.
We suggest you buy “choice,” “premium” or “select” treated boards. At about 40 percent more per linear foot, you’ll pay more, but the boards have fewer knots and straighter grain. And, since many of the higher grade choices are kiln-dried both before and after pressure treatment, they have less tendency to warp.