Treated wood is generally available as dimensional stock in 2x4’s, 2x6’s, 4x4’x, and 2x2’s for rail components. 5/4x6’s and 2x6’s for decking. 2x8’s, 2x10’s, 2x12’s for joists, stair stringers, and beams. 6x6’s for support posts. Also plywood.
The predominant species of treated wood is a regionally available softwood. Most common are:
Southern Yellow Pine - Southern Pine is the most common deck framing material in eastern United States. It is strong and stiff. SYP logs yield a high proportion of sapwood which works well to absorb preservative.
Red and Ponderosa Pine – Less strong than SYP, found in Northern U.S. and Canada.
Douglas fir – It is very strong and is less prone to warping and spitting than SYP. Predominant material found in western United States and Canada
Hem-fir – It is weaker and more prone to warping and splitting than Douglas fir, but more receptive to preservation. It encompasses a group of western species.