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Product Labels

Any new lumber treatments — including micronized products — have to run a tough gauntlet in order to be accepted by the code and the marketplace. There are two pathways to gaining code acceptance. One is to get “standardized” by the AWPA; the other is to acquire an evaluation report, or ER, from the International Code Council Evaluation Service (ICC-ES). While both listings are expensive to obtain, either one — plus continual inspections by an accredited agency like the Southern Pine Inspection Bureau — qualifies the product to carry an identifying plastic tag, stapled to the end of the board, with information contractors can use to choose their lumber. In addition to the inspector’s logo, the tag lists an AWPA “use category” or an ICC “exposure category” that tells the builder where the material is safe to use (see “Read the Label”).

Read the Label

Like everything else about treated wood, the plastic labels stapled to the end of each board have been changing. Until recently, the end tags carried information about the “retention level” of the treating chemical in the wood. That practice started back in the days of CCA, when most wood in the lumberyard was rated for ground contact and treated to a retention of .40 pounds per cubic foot. Now, however, retention levels vary from one chemical treatment to another and by lumber dimension. Because of the high cost of the new treatments, manufacturers typically use less chemical in, for example, decking boards or 2-by lumber than in 4x4s, which are more likely to be used in contact with the ground.

Accordingly, most suppliers now leave retention levels off the tag, preferring instead to simply recommend where the piece of wood should be used. (You can still find out the retention level by contacting the treatment company directly or by downloading the product’s evaluation service report, or ESR, from either the company’s Web site or the ICC Web site: ESR numbers are supplied on the lumber end tags.)

Retentions aside, even the usage labeling can be a little confusing. There are actually two systems for listing the allowable use conditions for treated wood. The American Wood Protection Association (AWPA) has a system of “Use Category” designations. Lumber stamped UC3A, UC3B, or UC3C, for instance, is approved for above-ground applications, while UC4A and UC4B indicate ground-contact applications. The International Code Council, by contrast, has chosen to go with basic descriptive words: Decking Use, Ground Contact, and Above Ground are the labels applied to almost all lumber you’ll see stocked at a lumberyard, often along with the AWPA designation. Lumber with heavy treatment retentions can be labeled Foundation Use or Marine Grade.

For deck builders, the new system can cause problems. Jim Finlay, who operates an Archadeck franchise in suburban Boston, explains: “Pretty much all CCA lumber used to be certified for ground contact. But with ACQ, only the large timbers — the 4-by dimension lumber and larger — is certified for ground contact.” That’s fine in most applications, says Finlay, but sometimes he needs to build a ground-level deck that requires a support beam placed at or below existing grade. In that situation, he says, “we dig out a slot in the ground, fill it with crushed stone, and put our beam on top of a concrete footer.”


Treated-wood end tags identify the brand of lumber, provide an evaluation service report number, and specify Above Ground, Ground Contact, or other permitted uses.

To get 2-by lumber for a built-up beam that’s rated for ground contact, says Finlay, he has to special-order the pieces. “I have yet to find a lumberyard where I can walk in and buy a 2x8 or 2x10 rated for ground contact,” he says. He is also still able to special-order CCA-treated 2-by stock for that application.

Ground contact, says wood scientist Mike Freeman, is by far the toughest exposure. “The wood is much wetter,” he notes, “and there are also increased fungal populations in the ground.” The ground line, he says, “is the No. 1 area where utility poles fail in the United States, and that’s the same for deck posts.” So contractors need to be sure they’re using the wood in accordance with its labeled exposure category — and be especially sure that they’re not putting wood labeled for above-ground use in contact with the earth.

On the other hand, says treated-wood expert Peter Laks, you don’t want to use more heavily treated wood than is required — at least not the copper-based products like ACQ or copper azole. Since wood rated for ground contact has more copper in it than wood rated for above-ground use, it’s not only more expensive — it’s also more likely to corrode steel and aluminum and to interfere with paints and stains.

To bring their products to market, some manufacturers will obtain an evaluation report first, because the process is faster, then later add or replace it with the AWPA listing, which requires more years of test data and is considered by some industry insiders to be a more rigorous method of certification. For example, while MCQ has received an ICC evaluation report, its manufacturer, Osmose, has not at this time applied for an AWPA listing. The two other manufacturers of micronized lumber, Arch Treatment Technologies and PhibroWood, are working to obtain AWPA listings for their products.