There are three types of lumber that are appropriate for exterior applications, which are not preserved with chemical treatments. These are the Western red cedar, cypress, and redwood. The cost and availability of these woods depend on your geographic location. For instance, in the western part of the United States, redwood is abundant and widely used.
In the Midwest, western red cedar is widely available. In the South and Southeast, and eastern parts of the country, cypress can easily be found at very reasonable prices.
Redwood and western red cedar have a straight grain. They resist decay, and they are are stable in their dimensions. However, they are prone to splitting when fasteners are driven in. In addition, these woods leak tannins that result in staining around the fasteners. These stains can even leak through paint, which poses a problem on painted surfaces. However, if the wood is prepped properly, it can be stained and finished nicely.
Cypress is shaped like a cone. It grows in swamps, and the roots grow past the water level. The color of the heartwood ranges from a light-yellow brown to a reddish or dark brown. Sapwood is close to white. Cypress found inland has heartwood that has a lighter color. The lovely grain is similar to that of ash, and it can be finished beautifully, just like cedar or redwood.
Lumber Treated With ACQ Is A Good Value
In early 2004, alkaline copper quat, or ACQ, treatment replaced the old chromated copper arsenate (CCA) treatment which had arsenic in the formulation. It held up well against rot and insects. Although ACQ treated lumber can still shrink, warp, or crack, this water-based treatment is the most common choice among other treatments.
In the treatment process, the preservative is forced into a lumber like the Southern yellow pine. When the lumber is saturated, it is banded and shipped. Because the treatment adds a tremendous amount of weight to the wood, it is subject the problems mentioned earlier. These problems can be avoided if the treated lumber is air-dried for two months during the warm season. Another method is to buy lumber that has been “kiln dried after treatment”, or KDAT.
The disadvantage is that KDAT usually costs twice as much as wet wood, and the lumber must be be special-ordered in advance from the home center or lumberyard. Only sapwood can accept preservatives well. Pressure-treated lumber that is heartwood does not resist decay. Instead of green, the color can be pink or tan.
Keep these lumbers in mind for your next woodworking project. They will definitely make the difference in the finish and the overall structure of them.