Pressure treated wood is wood that has undergone a process to make it more durable so that it is not susceptible to water, rot, termites, or fungus. It is used for a variety of applications ranging from outdoor decking to utility poles, from railroad ties to playground equipment. Boat docks, aquarium stands, and indoor pools are a few more examples. This type of wood conserves and extends a valuable renewable resource and it is economical.
To make the wood so long lasting, it is first treated with chemical preservatives, then placed in a cylinder under pressure. The pressure forces the chemicals deep into the wood, which then becomes a barrier against natural enemies like termites and decay. The effectiveness of pressure treated wood has been born out by the U.S. Department of Agriculture Forest Service in more than four decades of field testing. Because of its known efficacy, it is often guaranteed against termite infestation and decay for 40 years.
There are three main types of preservatives used in pressure treated wood: water-born preservatives, creosote, and oil-borne preservatives.
For residential indoor and outdoor use, wood treated with water-born preservatives is ideal. Some water-born preservatives are chromated copper arsenate (CCA), ammoniacal copper zinc arsenate (ACZA) and ammoniacal copper quat (ACQ). This type is also used for many commercial and industrial applications, including traffic signposts and noise barriers.
Some uses for wood treated with creosote preservatives are bridges, guardrails, and docks, while utility poles, crossarms, and indoor pools are a few examples of things made from wood treated with oil-born preservatives.
Pressure treated wood is claimed to be safe in studies conducted by the Environmental Protection Agency (EPA). The chemical preservatives, most notably arsenic, have not been found to leach into soil or water. Laboratory studies independent of the EPA also found no increased risk of cancer among those who work with treated wood on a daily basis.
According to research conducted by the Texas A&M Laboratory along with the Southwest Research Institute, wood treated with water-born or creosote preservatives is even safe to use in the vegetable garden among edibles, such as a trellises for tomatoes or vineyard support for grapes. However, the wood itself should not be consumed by humans or animals, and therefore should not be used where it might inadvertently end up in foodstuffs or feed. For example, a cutting board should not be made of pressure treated wood.
If you are looking to build something that will last, consider the advantages of using pressure treated wood. It is available at most lumberyards and home improvement centers. Just look for a stamp or tag of approval by the American Wood-Preservers Association (AWPA) or the American Lumber Standards Committee (ALSC).