There are various chemical preservatives used for treated wood. All chemical preservatives used in treated wood are registered pesticides and as such, they are regulated by the US EPA. The American Wood Protection Association (AWPA) writes various standards that determine use levels for wood preservative formulations as well as their suitability for the intended end-use in treated lumber. Third party inspection agencies regularly perform audits to ensure that quality products are produced in accordance with the standards. Below are common treated wood preservatives for Southern pine.
Common Treated Wood Preservative Protection Categories
Wood Preservative Treatments
- Topical/surface treatments for wood usually limit protection to the surface area as it is applied by brushing, spraying or dipping. Although regularly coating a surface with a paint or sealer may help protect wood from the elements, it won’t necessarily prevent it from rotting or being attacked by insects.
- Pressure-impregnated - Preservatives are infused into the wood, beyond just the surface. Pressure Treatment (PT) is the general term to describe the process for infusing/impregnating the wood fibers with preservative chemicals, removing any excesses, and leaving behind only enough chemical in the wood fibers (retention) to protect the treated wood. The AWPA sets appropriate chemical retentions depending on their intended use/requirements, based on performance data derived from long-term scientific tests. The AWPA wood preserving standards are reviewed by their technical committees every five years to ensure that retention levels are appropriate and that a given preservative formulation is performing as expected.
There are three categories of pressure treatments available for wood:
- Waterborne treated lumber is generally used in building structures that are residential, commercial and industrial.
- Creosote-treated lumber is mostly used for treating guardrail posts, railroad ties and timbers used in marine structures.
- Oil-borne treated lumber is used when treating utility poles and cross arms.
Preservatives & Treatment FAQs
What type of treated wood is recommended for raised vegetable and garden beds?
The construction of an in-ground, raised vegetable garden should use materials designed to withstand ground-contact exposure. Treated wood labeled for ground contact can be used near edible garden plants. Above ground contact labeled wood, such as Ecolife®, is not intended or approved for ground-contact exposure. Preserve CA pressure treated for ground-contact exposure, can be used around edible plants, and is available in 2x8's and wider as well as larger posts such as 4x4's or 6x6's which may work as the retaining wall or perimeter of a raised vegetable garden.
What is pressure treated wood preservative treatment and how does itwork?
Pressure treated wood is the application of a preservative formulation that is forced into the wood under pressure in a large cylinder. AWPA treatments are a safe and proven means to preserve and protect outdoor wood from decay and termite attack. Pressure treatments extend the life of wood, and reduce the impacts on forests, making them truly one of the most sustainable building materials used in the world today.
How are preservative chemicals applied to wood?
Wood products for construction are typically treated in a factory, using a pressure process. The product is loaded into a cylinder, and then the cylinder is filled with a solution containing the preservative chemicals. The vessel is pressurized to force the solution into the wood. Most dimensional lumber, as well as plywood, can be treated this way.
Why does wood need to be protected with preservatives?
Wood is an environmentally sound, economical building material that can be used either indoors or outdoors for a wide variety of structural and decorative applications. Unfortunately, untreated lumber cut from most commercially harvested tree species is subject to attack by insects or to decay caused by fungi and bacteria. The decay or insect hazard is greatest in exposures where the wood is subjected to moisture. Wood in outdoor exposures, either in ground-contact or in above-ground applications, is susceptible to attack. The potential for wood deterioration is greatest in hot and humid climates, which allow insects, fungi and bacteria to thrive. Destruction of untreated wood in aquatic environments can be caused by a variety of marine organisms. Wood should be treated with a preservative system to control the destructive activities of these organisms and ensure long-term structural soundness and serviceability.
What are the benefits of above ground pressure treated wood?
Lumber that has been treated to AWPA above-ground retention levels (UC3B) is standardized to provide a level of performance that is appropriate for above-ground applications. Proven above-ground products that meet the AWPA standards have historically performed well without the excessive use, or potential costs, associated with increasing those preservative levels for high-decay/ground contact level treatments.
Why is some treated wood green?
The green color you see on treated wood is caused by chemical reactions that take place between the preservative components and the wood. Copper is still the most widely used element in wood preservatives and creates a green color on the wood. As wood dries and reacts to sun’s ultraviolet rays, the green color will fade.
Treated wood is all the same, right?
No. All treated wood is not the same.
Above ground treated lumber is code compliant for use in applications where the wood does not touch the ground (e.g. deck joists and support beams used as critical structural members, decking, railings, and above ground fence pickets), or when use is six inches or more from the ground.
Wood treated to ground contact levels is required for direct contact with the ground (e.g. fence posts, etc.), and in cases where a high-decay hazard is very likely to occur (e.g. soil/leaves/debris build-up or accumulations are left to remain in contact with the wood, poor ventilation, tropical climates, etc.).
Our preservative products Ecolife® and Preserve® CA are treated under the AWPA standards for above ground or ground contact retentions to provide proven wood protection.
Ecolife, with its built-in wood stabilizing system, has been specifically designed for above ground use, and as such has been proven to perform. Ecolife treated wood exhibits reduced cracking, warping and splitting in service, and uses no more chemicals than is absolutely necessary.
Does the economy have anything to do with the quality of building products?
In this economy, everyone is looking for ways to save money and stay in business. The building products industry is no exception. With increased competition for sales and market share, lowering the quality of products or services is one way to save money. While a reduction in cost and quality might help some organizations survive on a short-term basis, it can have unintended long-term consequences. For this reason alone, it’s important to provide high-quality products and services to the public to maintain the trust of the customer to gain repeat business and positive referrals. AWPA has been the premier developer of consensus-based standards for treated wood products since 1904, which is why the building codes rely on AWPA Standards.
What is the difference between above ground and ground contact?
There are naturally-occurring fungi in the ground that attack lumber, so lumber destined to be used in the ground must be treated to a higher standard, or retention level, of fungi-resistant preservatives in the wood. The end tags on treated lumber will provide you with proper use designations. Look for Above Ground or Ground Contact on the end tag.
What are retentions or retention levels?
Retention levels refer to the amount of preservative retained in the wood following the treatment process. Retention levels can be different based on the wood preservative system used to pressure treat the wood product and its intended end use (ground contact, above ground contact, etc.). It is recommended to purchase treated wood products for the intended exposure condition. Typically, wood products are treated for “above ground use” and “ground contact use”. The treated wood end tag should state the recommended end use for the treated wood product.
Where can I learn more about the preservatives that are used to treat pressure-treated wood?
The American Wood Protection Association (AWPA) standards provide a list of standardized preservative formulations in the US. The AWPA standards are recognized worldwide, as their American National Standards Institute (ANSI) accredited process thoroughly evaluates, reviews and standardizes preservatives. AWPA standardized preservatives are approved by all building codes for their intended uses. Visit AWPA.com and their Technical and References sections for Homeowners, Specifiers, Builders and Retailers for more information.
Are your wood preservatives listed in the AWPA standards?
Yes. Viance’s residential preservatives are recognized and listed in the AWPA’s Book of Standards, which are referenced in the IBC and IRC building codes. Every preservative standardized by the AWPA is supported by rigorous laboratory and field test data that undergoes an extensive scientific peer review by industry-leading wood scientists, participating academics and independent industry experts/participants. To help ensure that AWPA-standardized products meet ongoing expectations, performance data is scrutinized every five years via the same peer review process to reaffirm its effectiveness.
Which wood preservative systems are standardized by AWPA?
In today's marketplace, there are many wood preservative systems available to the public. It is important that those wood preservatives reviewed by AWPA's Technical Committees and found in AWPA Standard U1 are selected at retentions that are appropriate for each Use Category. The following table is specific to Southern pine, but should be helpful in determining if the treated wood at your local retailer is treated with the correct preservative at the proper retention (expressed in pounds active ingredient per cubic foot of wood):
In 2020, the supply of quaternary used to manufacture ACQ was diverted for use in healthcare products brought on by the COVID-19 pandemic. All treaters switched over to CA (copper azole). To learn the similarities and differences in Viance's Preserve® CA and Preserve® ACQ treated wood, see the bulletin at this link.
What do the language changes in the AWPA-UCS guidelines mean for me?
It is important to select wood that has the appropriate level of preservative for its intended use. The language changes to the AWPA Use Category System and supporting guideline tables are intended to help clarify the scenarios where a higher level of protection should be considered/used. Material that is treated with Viance’s preservatives for Above Ground use is code compliant (IBC and IRC) and warranted accordingly. For cases where the material may be in higher decay environments/scenarios, a higher level of preservative protection is required.
How do I know if the treated wood I am using is properly treated for my intended use?
Look for a lumber end tag. Each piece of treated wood should have a tag containing information regarding the preservative used, the appropriate end use (Above Ground or Ground Contact) and the quality standard.
Ecolife® is standardized by the American Wood Protection Association (AWPA) and building code compliant (IRC and IBC). Ecolife-treated wood meets stringent industry standards and has the AWPA U1 and the CheckMark logo on the end tags as assurance that it has been quality-inspected by the American Lumber Standard Committee (ALSC) accredited third-party inspection agency.
Will deck joists and support beams treated to above ground retention levels (UC3B) remain building-code compliant under the American Wood Protection Association’s (AWPA) Use Category System (AWPA-UCS) guidelines?
Yes. The AWPA’s standards are directly referenced in the IBC and IRC building codes. The AWPA U1 standard will continue to allow above ground treated wood for use in critical deck joists and support beams, decking, railings, fence pickets, and many other outdoor project applications. Material treated and used for above ground construction with Viance’s preservative treatments will be covered under the terms of our Lifetime Limited Warranty, when used appropriately. This includes material used for above ground deck joists and support beams, which are critical to the performance and safety of an entire structure/project.
New language changes to the AWPA standards and supporting guideline tables can be somewhat confusing. These changes reference the use of (UC4A) retentions on treated wood components considered difficult to replace. Because the difficulty of replacement can be very subjective, standard deck joists and support beams treated to above ground retention levels (UC3B) remain code-compliant.
Products with increased chemical/retention amounts are needed for building components used in high-decay situations (e.g. within 6” of the finished grade and supported on permeable building materials, in tropical climates, when soil/leaves/debris are left to accumulate/remain and potentially replicate ground contact conditions, poor ventilation around decks, etc.).
Will ground contact treated wood be required for all deck joists and support beams?
No. Although all deck joists and support beams are critical to a structure, they all will not be required to be treated to ground contact retentions unless at least one of the following conditions occurs:
- when there is a reasonable expectation that soil, vegetation, leaf litter or other debris may build up and remain in contact with the component
- when the construction itself, other structures or anticipated vegetation growth will not allow air flow to circulate underneath the construction and between decking boards
- when components are installed less than six inches above the ground (final grade after landscaping) and supported on permeable building materials (e.g. treated wood or concrete)
- when components are in direct contact with non-durable untreated wood, or any older construction with any evidence of decay
- when components are wetted on a frequent or recurring basis (e.g. on a freshwater floating dock or by a watering system)
- when components are used in tropical climates
- when deck joists and support beams are deemed difficult to replace
Is ground contact treated material recommended for wood touching the ground?
Yes. Because conditions for wood decay are optimal in most soils, material treated for ground contact use is required. Ideal deck building techniques may include the use of non-permeable building hardware (fixed or adjustable), which are used as a barrier between a concrete footer and structural support posts/beams to potentially improve the performance of the treated wood. Measures should be taken to ensure that the accumulations of soil/leaves/debris are minimized or prevented during the project planning and construction phase. To extend the performance of the deck materials and components, regular inspection and maintenance should be performed.
Why is it important to have the AWPA identification on the end tag of the lumber I buy?
The AWPA is the only ANSI (American National Standards Institute)-accredited standards developer that requires a rigorous evaluation plus an open peer review of that data where the largest collection of wood chemical, wood technologists and wood preservers gather in North America for the express purpose of evaluating which wood preservatives are worthy to be standardized in the AWPA Book of Standards. If you are a homeowner, it probably means that you’re not content to simply ask for any kind of treated wood and that you want products that will provide years of service. You are likely searching the internet to find the product best suited to your needs, and you appreciate the value of wood treated to industry standards – standards developed by experts in the field of wood protection. Low-cost alternative preservative-treated wood is available, but you want products with proven performance. For more information visit the American Wood Protection Association (AWPA) web site.
How do I know my treated lumber and decking is treated to AWPA standards?
There are several key bits of information you should see on the treated wood end tags: First, look for “AWPA U1” on the end tag. If you cannot find "AWPA U1" and the Use Category, the wood probably does not meet AWPA Standards. Another helpful tool to identify wood treated in accordance with AWPA Standard U1 is the “CheckMark” program developed by the Western Wood Preservers Institute. The CheckMark, combined with the logo of an ALSC (American Lumber Standard Committee) accredited agency, demonstrates conformance to AWPA Standard U1.
Why should I require wood treated to AWPA standards?
Besides the fact that most architects and engineers specify AWPA Standards for treated wood, AWPA Standards are the only wood treatment standards listed directly in the IBC and IRC. You could use some of the low-cost alternative preservatives, but there is no guarantee or requirement that the designer or local code official will approve it. In addition, AWPA has over 100 years of history in developing reliable treated wood standards. Our standards are developed in an open, consensus-based, ANSI accredited process to ensure a stringent review of performance data while providing due process for all participants. Most of the world’s experts in wood protection actively serve on AWPA Technical Committees – a level of expertise unmatched elsewhere.
What do the AWPA Use Category designations mean?
The Use Categories are a shorthand method of describing the various hazards to which wood products may be exposed. A brief description of the Use Categories is shown, but if you would like additional details on the AWPA Use Category System, please download this excerpt from AWPA Standard U1.
Exterior Above Ground, Coated with Rapid Water Runoff
Exterior Above Ground, Uncoated or Poor Water Runoff
Ground Contact, General Use
Ground Contact, Heavy Duty
Ground Contact, Extreme Duty
Marine Use, Northern Waters (Salt or Brackish Water)
Marine Use, Central Waters (Salt or Brackish Water)
Marine Use, Southern Waters (Salt or Brackish Water)
Interior Above Ground Fire Protection
Exterior Above Ground Fire Protection
We have also developed an infographic that will assist you in determining the appropriate preserved wood for your particular project. You can download the Use Category infographic here.
How long will treated wood last?
Viance Residential Treated lumber products (Ecolife® & Preserve®) carry a Lifetime Limited Warranty against fungal decay and termite attack. We recommend annual cleaning and resealing to keep your project looking good.
What is incising and why is it required?
Incising is the process of cutting numerous small slits into the surface of a piece of wood in order to increase the amount of preservative taken up by the wood during treatment. Some Western wood species are particularly hard to treat, and incising is necessary to meet the penetration requirements in treatment standards.
Can I use treated wood inside?
Pressure-treated wood may be used inside, and is commonly used for the sill plates of homes and FRTW; fire-retardant treatments like D-Blaze® offer additional protection from fire and smoke development.
Properly dispose of all sawdust and construction debris after all projects. Many treated wood products do not emit any vapors and are safe for interior use. Check use information on specific products. Treated wood should never be used for countertops or where it may become a component of food. In fact, the Food and Drug Administration does not recommend using any wood for kitchen counter-tops or food-cutting boards because knife cuts may allow food particles to become entrapped, creating an unsanitary environment.
When should treated wood be specified?
Treated wood is required by building codes in numerous applications. Exterior wood treatment solutions extend the natural life of the wood used in construction applications and provide exceptional performance for outdoor projects. Treated wood may be specified for interior framing where termite attack is prevalent, or where fire retardant materials are needed.
Where can I find LEED information on Viance products?
All product and technical information pertinent to the Viance chemicals is available for download on the Product Information page. The wood and lumber products that are treated with Viance products come from various sawmills and wood treaters, so additional information on the lumber products must come from the actual lumber suppliers of the materials used in the project.
Product contribution points and building certifications for LEED and the National Green Building Standard (plus their web links) can be found on this compiled document that can be helpful indicating possible points from Viance preservative products.
Where can I find sustainable forestry information on Viance treatments?
All product and technical information pertinent to the Viance chemicals used to treat wood is available for download on the Product Information page. Sustainable forestry programs such as FSC or SFI are managed entirely by the companies that procure and resell wood through their distribution networks. Viance develops and manufactures only the preservatives/treatments used. All FSC/SFI information would be provided by lumber suppliers.
How much weight does treatment add to the weight of wood?
Most of the weight added to treated wood comes from water used to carry the preservative components. A freshly treated piece of lumber may contain as much as 2-4 gallons of water per cubic foot or about 16-32 lbs. per cubic foot. As the wood dries and the water evaporates, only the preservative will remain.
Is kiln drying or air drying recommended for treated wood?
Kiln drying after pressure treatment (KDAT) removes a large amount of the moisture from the wood. Most treated lumber products today are air dried. Kiln drying after treatment (KDAT), will add cost to the process and the finished products; however, KDAT wood tends to reduce warping, as it is a more controlled drying method.
Do your pressure-treated wood products contain formaldehyde?
Viance wood preservative products do not contain formaldehyde. However, the glues used in the production of plywood, laminates or other engineered wood products may contain formaldehyde. Contact the engineered wood producer for information regarding the use of formaldehyde in their products.
What kind of stain or paint should I use to protect treated wood used on outdoor projects besides my deck?
AWPA member Sam Williams and his colleague, Mark Knaebe, both from the USDA Forest Products Laboratory (FPL) in Madison, Wisconsin, have published a number of excellent papers on the subject which are posted to the FPL's website at this URL: https://www.fpl.fs.fed.us/prod...
In general, they recommend a semi-transparent, oil-based penetrating finish stain, and we agree with their findings.
What preservative treatment do you recommend for field-cut board ends?
For exterior project applications, treat all field-cut ends of boards and drilled holes with a brush-on wood preservative. Copper naphthenate formulations are available from home centers, lumber dealers and hardware stores. Deck stains and sealers do not provide adequate protection.