Pressure Treated Deck Builder in Charlottesville, VA

Pressure Treated Decks // A Wood for All Seasons

Pressure-treated deck wood is truly a "wood for all seasons" — a rugged exterior building product that's rot- and insect-resistant.

Treated wood is used for decks, mailbox and light posts, swing sets and playscapes, picnic tables, landscape ties, underwater dock pilings, oceanside boardwalks, telephone utility poles, and — believe it or not — residential building foundations in some parts of the country.

Its unique ability to fend off decay makes it ideal in any high-moisture and/or ground-contact installation.

Yet there is much misinformation — and in some cases disinformation — concerning pressure-treated wood, its maintenance requirements, and its safety in common use.

What is Pressure-Treated Wood?

Over 70 years ago, Dr. Wolman invented the process of infusing preservative deeply into wood products.

Pressure treating is a process that forces a chemical preservative deep into the wood. The wood product is placed into a large cylindrical holding tank, and the tank is depressurized to remove all air. The tank is then filled with the preservative under high pressure, forcing it deep into the wood.

This process makes the wood unappetizing to vermin, insects, and fungus — which accounts for its 20+ year lifespan under the harshest conditions.

What chemical preservative is used? Is it dangerous?

Until 2003, the preservative most commonly used in residential pressure-treated lumber was chromated copper arsenate (CCA), an extremely toxic chemical.

However, one must distinguish between the toxicity of the chemical and the toxicity of the wood product in everyday use. Extensive studies were done since the mid-1980s concerning the potential dangers of pressure-treated wood as large volumes of CCA were being used, and the treated wood products were beginning to be widely distributed, justifying the need for hard research.

The research was mixed, but the typical hysteria ensued as attorneys and plaintiffs lined up to claim damages from exposure to CCA. In the end, the industry agreed to voluntarily eliminate the use of CCA for residential use. CCA is still being used in certain marine and industrial applications since it remains the best preservative available for those purposes.

More Q&A on Pressure-Treated Lumber

Are the modern (post-CCA) replacements equivalent? Yes.

Following the safety rules regarding cleanup should be sufficient. However, these newer products are extremely corrosive to steel and aluminum. Fasteners and construction hangers/ties should be rated for use with the new wood. Any aluminum flashing should be covered with an impervious layer of a non-corrosive material such as tar paper or non-permeable plastic sheets to prevent contact with the wood.

Should I tear out an existing CCA deck? Absolutely not. Existing decks pose no danger and, in fact, tearing them out may release more chemical than leaving them in place. (See safety precautions below.)

The EPA has stated that applying a penetrating oil finish as needed to pressure-treated wood surfaces that have human contact can lessen or eliminate human and animal exposure to CCA in existing decks. Studies show a dramatic decrease in the amount of arsenic at the surface of the wood for periods up to two years when compared with unsealed wood.

Though the infused preservative prevents rot, it does not inhibit weathering. The effects of the elements on pressure-treated wood are no different than with ordinary wood. A preservative is a must — and should be applied as soon as possible after your project is completed.

Health and safety: a certain amount of PT preservative will leach to the surface of the wood over time. Applying a coating every year or two (once the rain stops beading) greatly lessens the amount of preservative that leaches to the surface.

Applying a preservative slows drying, inhibits shrinkage, and helps maintain a smoother surface. The sun takes no prisoners — even pressure-treated wood needs protection from it. The preservative protects the wood from mold and mildew.

The preservative should be applied immediately upon completion of the project, or within a month or so if the wood is especially wet.

Be sure that the preservative you purchase is recommended for use with pressure-treated wood.

Staining and Painting

Many manufacturers carry full lines of both oil and latex products that can be used on pressure-treated wood. According to Cuprinol, you should wait at least one to two months before staining. You may apply a clear preservative immediately, but it must be a product manufactured for use on fresh pressure-treated lumber.

What about painting? Don't even think about painting fresh pressure-treated wood. The moisture in it stacks the deck against good paint adhesion. Seal your project with a pressure-treated wood preservative immediately and follow the preservative's instructions regarding future painting, making special note of the amount of time the preservative should weather before painting.

Applying a sealer can protect against CCA exposure: according to the EPA, studies show that the application of a penetrating oil finish can reduce or eliminate exposure to CCA in older decks and to the chemicals used in newer decks. So it's recommended that all pressure-treated surfaces with human contact be coated with an oil finish as needed. Note that paints and opaque exterior stains do not offer the protection of stains that are absorbed more deeply into the wood.