Preservative Treated Wood – What Does it Mean?

Texture of wood background closeup

Wood is an extremely durable material. Properly dried, finished and sealed, wood can last for thousands of years, assuming it’s protected from water, high humidity, and insects.

The irony is that when wood isn’t protected from the elements, this durable material degrades rapidly. There are certain species, like cedar, that are naturally resistant to rot. But humans have been using technology for millennia to try and preserve wood beyond its normal lifespan. This was the advent of preservative-treated wood — wood that has been treated in some way to protect it from rot and extend its life.

There are records from ancient Greece that mention wood bridges soaked in olive oil, and the Romans coated the exterior of their wood ships with hot tar. This technology didn’t change a lot until the Industrial Revolution when new methods for wood preservation began development.

The first patent for a preservative treatment for wood was filed in 1716, and since then a plethora of preservative treatments have been created, with varying degrees of success, in an effort to get extra years of life from exterior lumber.

Methods for Preserving Wood

There are a number of different chemical mixtures that impart resistance to the fungi, bacteria, and insects that break down wood and eat it. Depending on the application and the compounds in question, these treatments can be sprayed onto wood, cooked in, and deeply injected using high pressure. Additionally, sealants and water barriers don’t qualify as “preservative treatments” because they do not treat the wood fiber as found with preservative treatments.

Today, pressure-treating wood is the most common method for getting chemical preservatives into the structure of lumber. The process involves soaking lumber in a liquid preservative and then placing it in a pressure chamber which generates pressure sufficient to force the preservative deep into the fibers of the wood. This deep treatment provides much more robust, and longer-lasting protection than you would get with a simple exterior treatment. But for decorative, exterior application most high-pressure treatments are not ideal.

However, for wood that doesn’t make contact with the ground, like trim, and other decorative millwork, spray-on treatments are excellent, particularly using modern techniques. This is because the majority of wood-rotting insects, fungi, and bacteria gain access to wood from the ground. If wood doesn’t make contact there and is treated appropriately, it can last and last.

The Dangers of Wood Preservation

Many of the chemicals used in wood preservation can be toxic to animals and humans. Over the years, some have been found to leach out of treated wood and into the surrounding soil, creating a potentially dangerous situation, particularly if the wood leaches into food crops.

Certain compounds that were common in wood preservation in the early days, like arsenic, have long since been removed by government mandate. But with many products, care is still recommended to avoid any accidental ingestion of toxic chemicals.

A Safer Wood Preservative Treatment

In response to these toxic concerns, companies began devising new treatment methods that were far less dangerous and weren’t toxic to the environment. Lonza is one of these and their Wolman AG treatment process is the first non-metallic preservative that provides excellent protection for above ground lumber applications without the accompanying toxicity.

Belco Forest Products uses the Wolman AG process on all of their preservative-treated exterior trim products, XT Trim, XT Post and XT Beam. This process offers the protection consumers are looking for along with the peace of mind that comes from using an EPA registered, environmentally friendly preservative method.

If you’re an environmentally conscious contractor or consumer, Belco Forest Products provides the best choice for all your exterior millwork needs.

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