Information for Building Code
Building code officials are required to have in-depth knowledge
of all types of construction methods and the thousands of
different products used in modern buildings. The
International Code Council's committees recognize AWPA as the
authority on treated wood and have listed AWPA Standards directly
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
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:
||Exterior Above Ground, Coated with Rapid Water
||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
Do all end cuts need to be field-treated with preservatives?
As a best practice, 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). Exceptions can be
made when the wood is a thick sapwood species such as Southern
pine, has very little heartwood, and appears to be well treated.
Copper naphthenate specified in AWPA Standard M4 for field
treatment contains 2% copper and is available online from Copper
Care Wood Preservatives, under the brand name "Tenino".
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.