What is Treated Wood In Residential Construction?

Treated Wood

Exterior wood trim adds natural dimension and architectural interest to any home. But, separating facts from marketing fiction is a challenge with so many warranty limitations and manufacturers’ claims to digest.

This bulletin explains current industry standards for “treated” wood with respect to the use of “wood preservatives” language. Preservatives are what create long lasting wood products when subject to the elements. These preservatives protect end-users from future liability claims. Also, why protective coatings/sealers give limited protection against rot and decay compared to true wood preservatives.

What Is A Wood Preservative?

Wood preservation, as defined by the American Wood Protection Association (AWPA), the industry’s standards developer:

The technology of reducing and/or preventing the deterioration and destruction of wood by living organisms, particularly fungi, insects, and marine borers…through the application of wood preservatives.

Environmental Protection Agency (EPA) registration is required for true preservative chemicals. Preservative wood products must achieve a level of chemical penetration and saturation stipulated by agencies like AWPA. XT products by Belco feature Wolman AG® by Lonza which contains three EPA registered ingredients: propiconazole, tebuconazole and imidicloprid (also known as PTI). This assures the end user that there are sufficient preservative chemicals in the wood cells to prevent decay causing fungal growth and termite infestation. Belco’s quality assurance team processes include regular substrate sampling to verify adequate preservation levels.

Another professional association that sets performance standards for treated products is the Window and Door Manufacturers Association (WDMA). The WDMA Hallmark Certification Designation provides building professionals an easily recognizable means of identifying products made in accordance with standards.

The WDMA Hallmark is a mark of excellence among architects, contractors and other specifiers. It is accepted industry-wide for excellence.

HUD/FHA Minimum Property Standards reference WDMA standards. Government agencies also accept WDMA standards for construction specifications. Lonza’s Wolman AG® is an qualified preservative under these standards. (See https://belcofp.com/).

Does “Treated” Mean Preservative Treated?

The term “treated” does not necessarily mean the material is ‘preservative treated wood”. True preservative treated wood products carry the EPA approval designation.

It’s as simple as this: Ask your supplier if their treated lumber uses preservative chemicals registered with the EPA. If not, it isn’t a true wood preservative, period.

Claims of “treated” in the general sense of the word may be true. Unless labeled “preservative treated” the product does not use true wood preservatives. Preservative treated wood products using approved wood preservative chemicals state clearly the treatment chemicals and carry an EPA approval statement.

Wood preservatives are regulated chemicals. You will find in a routine search of the EPA chemical database true wood preservative chemicals. If it’s not in the database, it’s not a wood preservative.

About Primers and Paint

Mold and mildew additives are a common ingredient in primer and top coat paints. But they do not act to preserve wood fiber. These additives primarily inhibit topical mold and mildew growth. They have little effect on preserving the wood fiber.

Coatings such as sealers defend against weathering and may repel water from the wood surface. However mold and mildew additives do not prevent rot from fungi in wood. They inhibit mold and mildew on the surface of the lumber. Nearly all primers and paint products contain mold and mildew inhibitors.

Coatings with additives to resist mold and mildew, such as Iodopropynyl butylcarbamate (IPBC), are not sufficient to prevent rot and decay. Belco’s proprietary primers applied to all XT Products also utilize inhibitors like these to provide maximum weathering protection.

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