APB » Wood Treatment Levels

Wood Treatment Levels

Code Requirements:
IBC 2302.1.8
IBC 1809.1.2
IRC R319.1
IRC R320.3.1

Pressure Treatment Process
The process of pressure treating wood involves kiln drying the lumber, then placing the members in a cylinder, applying a vacuum, and then applying pressure to force preservatives into the wood.

Retention Levels
The amount of chemical absorbed by the member in pounds per cubic foot is used as a rating or retention level for pressure treated wood and lumber.

Chromated Copper Arsenate or CCA-C is not available for residential use due to the fact it contains arsenic. It is still used for foundation wood in many areas and is the recommended solution if available. The Forest Products Laboratory provides more information about different types of wood treatment.

Wood Decay
Preservatives are necessary to prevent decay of members due to insects and fungus. In many parts of the country common belief is that allowing concrete to "touch" foundation posts will cause decay. This is caused by purchasing the WRONG foundation post. Properly treated foundation posts will not rot due to contact with concrete, and some areas of the country embedment in concrete is required.

American Wood Protection Association
The AWPA is ANSI accredited and provides standards for wood chemical usage evaluating through rigorous testing of treatment methods and treatment levels for southern yellow pine and douglas fir wood species.


CodePreservative NameUC1/2UC3BUC4AUC4B
CCA-CChromated Copper Arsenate0.400.60
ACCAcid Copper Chromate0.250.250.50---
ACQAlkaline Copper Quaternary (Types A,B,C)
ACQAlkaline Copper Quaternary (Type D)
ACZA Ammoniacal Copper Zinc Arsenate 0.25 0.25 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
CuN-W Waterborne Copper Naphthenate 0.070 0.070 0.11 ---
CX-A Copper HDO 0.206 0.206 --- ---
EL2 DCOI-Imidicloprid-Stabilizer 0.019 0.019 --- ---
PTI Propiconazole-Tebuconazole-Imidicloprid 0.013 0.018 --- ---
PTI PTI plus Stabilizer 0.013 0.013 --- ---
SBX Inorganic Boron (Formosan termites) 0.28 --- --- ---
SBX Inorganic Boron (non-Formosan termites) 0.17 --- --- ---

"AWPA Technical Information." AWPA - American Wood Protection Association. Web. 23 Oct. 2010. http://www.awpa.com/references/homeowner.asp"