Hemlock
Hemlock is readily pressure treated with preservatives. Such products, generally in dimension lumber grades and sizes, are widely used for backyard outdoor decks. Hemlock is the preferred Western species group for preservative pressure treating. Because of its combination of strength properties and beauty, this species combination is useful for both the load-bearing as well as non-structural components of outdoor installations. With incising (small cuts are made in the surface of the wood before treating), Hemlock may be treated to appropriate retention levels for above-ground, ground-contact, or in-ground installations.
Douglas Fir
Treated DF products are consistently found in foundation stud and plywood walls, vehicular bridges, walkways, parks shelters and foot bridges. Douglas Fir preservative pressure-treated wood pilings provide long-life performance with resistance to the corrosive salt water conditions of wind, waves, storms and tides. When dramatic design solutions are called for on hillsides or in hurricane country, pressure-treated Douglas Fir pole construction is often the best and most economical solution. Design loads as high as 70 tons have been specified and ultimate loads as high as 235 tons have been carried by Douglas Fir lumber.