Information for Building Code Officials

Building code officials are required to have in-depth knowledge of all types of construction methods and thousands of different products used in modern buildings.  The International Code Council's committees recognize AWPA as the authority on treated wood and have directly referenced AWPA Standards in the International Building Code and International Residential Code in applications where preservative treated wood is required.

How do I make sure the treated wood on the jobsite meets code?
AWPA's standards are the only standards for treated wood directly listed in the IRC and IBC, so the first thing to do is look for "AWPA"  and the applicable standard, usually "U1" on the end tag.  It's also important to look for the preservative code and retention (amount of preservative retained in the wood), for example, "ACQ-D" or "CA-C".  You should also look for the appropriate AWPA Use Category for the application, such as UC3B or UC4A.  Note that in most cases, wood treated to a higher Use Category may be used for applications in a lower Use Category.  For example, sill plates are a UC2 application, but you may use wood treated to UC2 requirements or higher, such as UC3B.  A listing of AWPA Use Categories is found below:

Use Category Brief Description
UC1 Interior Dry
UC2 Interior Damp
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.

Do all end cuts need to be field-treated with preservatives?
When wood is pressure treated with preservatives, it is absorbed in varying amounts by the sapwood, but only a small amount of preservative penetrates the heartwood, juvenile wood, and some of the wood surrounding knots.  Therefore, all drilled holes and cut ends need to be treated with a preservative, such as copper naphthenate or oxine copper (mostly for exterior use) or a boron-based preservative (for interior uses only).  Copper naphthenate specified in AWPA Standard M4 for field treatment contains 2% copper and is sometimes available in paint, hardware, or building supply stores, as well as online from Poles, Inc., under the brand name "Tenino".  The only commercially available oxine copper product we're aware of is called "Outlast Q8 Log Oil", and it is normally found at log home supply companies.  For borates, commercial products such as "Bora-Care" may be used, but saturated solutions of borax and/or boric acid in hot water may also be used.

How can I get wood tested to see if it has been pressure treated and to determine the amount of preservative in the wood?
AWPA’s Analytical Standards include several standard methods for detecting the presence and amount of preservative elements in wood.  Several of the wood treatment inspection companies can also inspect the wood, take the necessary samples and run the analytical procedures to determine if the wood has been treated and ascertain the remaining amount of preservative in the wood.  Some of the companies are sponsors of AWPA and can be located by going to our "Suppliers and Sources" page.

The builder did not use pressure treated wood in locations required by the code.  Is there a preservative that can be applied to make it comply with AWPA Standard U1?
Unfortunately, no.  Except for dip-treated millwork or composite wood products with a powdered preservative incorporated with the wood strands, fibers, or chips during the manufacturing process, Standard U1 requires pressure treatment for all other products.  Some surface-applied preservatives might provide some degree of protection, but it would not be as effective as pressure treatment, which forces the preservatives deep into the wood.