Information for Homeowners
If you're a homeowner and you've navigated to this page, it probably means that you're not content to simply ask for any kind of treated wood...you want 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. We hope that the following information is helpful. If you have additional questions, please be sure to contact us.
Why is it important to have "AWPA U1" on the end tag of the lumber I buy?
The AWPA is the only ANSI-accredited standards developer that requires a rigorous evaluation plus an open peer review of that data where the largest collection of experts in the field of wood protection in North America gather for the purpose of evaluating which wood preservatives are worthy to be standardized in the AWPA Book of Standards. AWPA Standard U1 is the primary standard for the specifications for preservative treated wood.
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 levels 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 (the nominal retention amounts below are expressed in pounds active ingredient per cubic foot of wood):
|Code||Preservative Name||UC1, 2||UC3B||UC4A||UC4B|
|ACQ||Alkaline Copper Quaternary (Type B or C)||0.25||0.25||0.40||0.60|
|ACQ||Alkaline Copper Quaternary (Type A or D)||0.15||0.15||0.40||0.60|
|CA-B||Copper Azole, Type B||0.10||0.10||0.21||0.31|
|CA-C||Copper Azole, Type C||0.060||0.060||0.15||0.31|
|Cu8||Oxine Copper (Copper 8 Quinolinolate)||0.020||0.020||---||---|
|CuN-W||Waterborne Copper Naphthenate||0.070||0.070||0.11||---|
|KDS||Alkaline Copper Betaine||0.19||0.19||0.47||---|
|MCA||Micronized Copper Azole||0.060||0.060||0.15||0.31|
|MCA-C||Micronized Copper Azole, Type C||0.050||0.060||0.15||0.31|
|PTI||PTI plus Stabilizer||0.013||0.013||---||---|
|SBX||Inorganic Boron (Formosan termites)||0.28||---||---||---|
|SBX||Inorganic Boron (non-Formosan termites)||0.17||---||---||---|
How can I make sure the treated wood I buy complies with AWPA Standards?
There are several key bits of information you should see on the treated wood end tags:
"AWPA U1" signifies that the wood is treated in accordance with AWPA Standard U1, the primary specification for treated wood. The AWPA Use Category designation (for example, "UC2", "UC3B", "UC4A", etc. - see below for descriptions) indicates the proper usage of the treated wood product. The preservative name or abbreviation, along with the AWPA U1 specified nominal retention (a number such as "0.060" or "0.31") will also be printed on the end tag. On wood intended for applications subject to building codes, you should also see a "checkmark" logo and the "quality mark" of an ALSC accredited agency. If you cannot find "AWPA U1" and the Use Category, the wood probably does not meet AWPA Standards.
Is treated wood safe for raised bed gardening?
AWPA is primarily a standards developer, much like ASTM, but specific to products and processes which increase the longevity of wood products. As such, our expertise is in wood durability, and NOT human health and safety. We rely on the U.S. EPA to determine product safety during their registration process. It is our understanding that the wood preservatives used in treated wood available to consumers have been registered by EPA for general use, which means that EPA has determined it is relatively safe for most, if not all, consumer applications. Different people perceive safety in different ways. If you're concerned, you could always put a sheet of plastic between the treated wood and the soil if you want to minimize or eliminate contact between wood and soil. Please note that some treated lumber that is two inches or less in thickness may only be treated for above-ground uses, so it may not last very long in a ground-contact application. Ground contact applications require an AWPA Use Category 4A (UC4A) or higher. For product safety information, be sure to contact the manufacturer of the treated wood product or the manufacturer of the wood preservative chemical. There should be contact information on the end tag of the treated wood at your lumber retailer.
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.
|Use Category||Brief Description|
|UC3A||Exterior Above Ground, Coated with Rapid Water Runoff|
|UC3B||Exterior Above Ground, Uncoated or Poor Water Runoff|
|UC4A||Ground Contact, General Use|
|UC4B||Ground Contact, Heavy Duty|
|UC4C||Ground Contact, Extreme Duty|
|UC5A||Marine Use, Northern Waters (Salt or Brackish Water)|
|UC5B||Marine Use, Central Waters (Salt or Brackish Water)|
|UC5C||Marine Use, Southern Waters (Salt or Brackish Water)|
|UCFA||Interior Above Ground Fire Protection|
|UCFB||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.
What kind of stain or paint should I use to protect treated wood used outdoors?
The USDA Forest Products Laboratory in Madison, Wisconsin, has published a number of excellent papers on the subject which are posted to the FPL's FinishLine publications page. In general, they recommend semi-transparent oil-based stains, and we agree with their findings.