May 27, 2024

Commonly used in home building and improvement projects, lumber—a collective term applied to harvested wood—is vulnerable to the elements in its natural state. Thus, there are measures taken to extend the life of wood products used for building significantly. Such wood products are referred to as pressure-treated lumber.

The Purpose of Pressure Treating Lumber

Treating wood, or lumber, is called pressure treatment; it is also known as timber treatment (British English) or lumber treatment (U.S. English). Pressure treatment is meant to protect the lumber from decay from fungi and attacks from insects such as termites. Such protection consequently prolongs the life of the material. Pressure treatment also provides an aesthetic benefit. Homeowners can be assured that the wood used for structures like patios, decks, cabinetry, and window sills will not only last for a long time but also look good for a long time as well.

Preservatives in Pressure Treated Lumber

The “pressure” comes from the pressurized cylinder the lumber is placed in and “treated.” A waterborne preservative is applied deep into the chemical structure of the wood. These wood preservatives are usually a mixture of different chemical elements, each with a specific function. The most common concoction, chromate copper arsenate (CCA), is an amalgamation of copper, arsenate, and chromium. The copper repels fungi; and the arsenate, derived from arsenic, acts as an insecticide. The chromium—which has little preservation power, if any—is added to the mix to bind the copper and the arsenate to the wood. Less common wood preservatives include ammoniacal copper arsenate (ACA) and ammoniacal copper zinc arsenate; they are used as alternatives to CCA, which is the world’s most widely used wood preservative.

Maintenance of Pressure Treated Wood Products

A common misconception of pressure-treated lumber products is that it does not need maintenance due to the infusion of wood preservatives. However, to maintain their appearance, homeowners would need to employ a coating of water repellent from time to time. Lumber tends to split and crack due to moisture transfer between the lumber and the surrounding environment. Such exposure causes stress to the material, thus resulting in wear and grain separation; and the wood can crack as it dries up. It is recommended that the pressure-treated wood product gets water repellent immediately after installation.


Pressure-treated lumber products are not created equal. Some companies provide materials that meet certain quality standards. Two of the most popular certification programs are Environmentally Preferable Product (EPP) and Leadership in Energy & Environmental Design (LEED) certifications reward companies dedicated to eco-friendly pressure custom-treated lumber.

Safety and Handling

The U.S. Environmental Protection Agency (EPA) sets the guidelines for the production and use of pressure-treated lumber. The agency has not concluded that treated wood is harmful to people or the environment, and it is currently evaluating the potential risks of pressure-treated wood products on people. In the meantime, the agency recommends that people limit the amount of exposure to such products. This can be done by wearing a dust mask, goggles, and gloves; sawing and sanding the wood outdoors; thoroughly cleaning areas of all construction debris; and taking a thorough bath after working with the wood.

The aforementioned precautions are designed to reduce the chances of inhaling or ingesting particles from pressure-treated lumber. The extent of the impact on the environment is also being evaluated by the EPA. Although pressure-treated lumber leaches chemical elements into the surrounding soil, the EPA is yet to determine whether there is a long-term adverse impact on plants and animals.

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