MD210.8.3, ENG - Preservative Treated Wood

Maryland Bulletin: 210-8-3
Subject: ENG - Preservative Treated Wood
Date: May 14, 2008

Purpose. To clarify industry changes resulting from the reduced usage of CCA treated wood.

Expiration Date. September 30, 2008.

Explanation. 

Evaluation Service Reports (ESR) is a relatively new development in the pressure-treated wood arena. Following the formation of the International Building Code (IBC), the International Code Council (ICC) set up a way for manufacturers and suppliers to document code compliance for “new and innovative” products that are not specifically cited in the IBC. The ICC Evaluation Service, Inc. was formed February 1, 2003 and provides independent testing of products to confirm whether or not they are IBC-compliant.

Specifically related to wood preservatives, the primary basis for compliance with the IBC for preservative treated wood products is that a product meets all the applicable standards in the American Wood Protection Association (AWPA, formerly the American Wood Preservers Association) Book of Standards. The testing that ICC-ES does is essentially identical to what the AWPA would do. The same standards are used across the board. They test not only production processes, but also field performance. If the ICC-ES testing finds that a preservative meets the AWPA standards, they will issue an ESR-Report. This report constitutes acceptable documentation of compliance with the IBC for preservative-treated wood.

In 2007, the AWPA has changed from a Commodity Specification (C##) to a Use Category (UC##). The use category is the same for AWPA and ICC. Therefore until all standard construction notes and drawings have been changed to reflect the above information, treatment levels as specified below are acceptable.

The use category for PPT posts shall be UC4B. The use category for PPT lumber shall be UC4A.

The PPT wood should have a label attached to each piece. The use category shall be included on the labels. For NRCS post-frame structures, the use category shall be UC4A or UC4B, unless otherwise designated. The retention level and the testing criteria, either AWPA or ESR reference number, shall be included on each label.

Attached is an excerpt from AWPA U1-07 which provides an introduction to the Use Category System followed by some sample product labels.

ALLAN H. STAHL
State Conservation Engineer

Attachment (PDF; 539 KB)

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