scope:

INTRODUCTION TO THE USE CATEGORY SYSTEM

The Use Category System (UCS) of the American Wood Protection Association (AWPA) designates what preservative systems and retentions have been determined to be effective in protecting wood products under specified exposure conditions. The strength of the UCS and its focus is that all wood uses can be placed into one of five major Use Categories that clearly describe the exposure conditions that specific wood products can be subjected to in service. The major Use Categories are further broken down into subcategories to define the associated degree of biodegradation hazard and product service life expectations for specific products and exposure conditions. In addition to the five Use Categories for biodeterioration, there is a sixth and separate Use Category for fire retardant applications. The Use Category designations are described in detail in Section 2 below. The Use Category system is designed to help specifiers and product users locate the appropriate AWPA Standards that provide listing of preservatives deemed acceptable for specific products and end-use environments. The user of the AWPA Standard U1 should first become familiar with the major differences between the Use Categories and the expected service conditions as described in Section 2. This information is then used in conjunction with Section 3: Guide to Treated Wood End Uses to determine the specific Commodity Specification of the Standard that lists the appropriate preservative requirements for that use. When purchasing under the Use Category System, material orders should include the specific commodity, Use Category designation, Standard U1 Commodity Specification, wood species, preservative and any special requirements such as preor post-treatment preparations (including conditioning and drying). Wherever practicable, material should be manufactured in its final form prior to treatment to eliminate the necessity for subsequent cutting or boring of the treated wood. Risk assessment documents and models (e.g., Best Management Practices) have been developed by the Western Wood Preservers Institute (www.wwpinstitute.org) for the use of CCA, ACZA, Creosote, Pentachlorophenol and ACQ treated wood in aquatic environments. Projects calling for large volumes of treated wood immersed in (i.e., below the splash zone) poorly circulating bodies of water should be evaluated on an individual basis using risk assessment procedures. There are a number of other AWPA Standards that compliment Standard U1 for wood treated with preservative systems. These include:

Standard T1: Use Category System: Processing and Treatment Standard, that governs the preservative retention and penetration requirements, processing limitations, quality control and inspection requirements for treated wood.

Miscellaneous (M) Standards for Quality control and inspection items

Analytical (A) Standards to determine conformance of preservative systems, penetration, and retention. Refer to the Introduction to this Book of Standards at the front of this edition for additional information.