Last fall, I set out on a quest to find some PT framing lumber that was rated for ground contact. I spent a little time prowling the aisles at my local Home Depot and Lowe’s, then later visited or called a few local lumberyards, in all cases with little success. Sure, I could have special-ordered whatever I needed, but none of the dealers I contacted actually stocked any framing lumber with AWPA or ICC-ES UC4A tags stapled to the ends. Almost universally, except for PT posts, all they carried was above-ground treated material.

I repeated the exercise a few days ago, and found that the situation is changing. This time, all the local lumberyards I called told me that they either had already switched or were in the process of switching over to all ground-contact treated lumber. I know of several large dealers in other markets who are making the switch too. Geoff Case of Home Depot said that the giant retailer is in the process of converting all of its 1-by and 2-by wood products to ground-contact retention levels in all of their stores, though I didn’t see any evidence of that at my local store or in an online search.

If you’ve been following the decking news on the PDB website, you know that these changes follow the announcement this spring that the American Wood Protection Association is revising its AWPA Standard U1 for preservative-treated lumber. That’s the standard that building-code requirements for deck construction are based on. The revised version won’t actually be published until May or June of this year, and after that, it will take a while before the IRC adopts the new standard; just how long it will take for those changes to trickle down to state and local codes is anyone’s guess. So the apparent marketplace move toward ground-contact material that I’m seeing this spring comes as a bit of a surprise. After all, above-ground treated lumber is currently less expensive than ground-contact material and, as Viance president Bill Fields noted, remains acceptable under IBC and IRC building codes for most common deck-framing applications.

The question is, will it still be OK to use UC3B material for deck framing once the revised Standard U1 is adopted, whenever that turns out to be? Unfortunately, the new standard—which raises this question in the first place—isn’t particularly helpful in answering it, especially when it includes language like this: “Joists and beams shall be treated to requirements for UC4A when they are difficult to maintain, repair or replace and are critical to the performance and safety of the entire system/construction.” Huh?

Colin McCown, AWPA’s executive vice president, admitted that the phrase “difficult to replace” has created some controversy in the industry. “Some are saying that all joists and beams are difficult to replace, and others are saying that they’re only difficult to replace in certain circumstances,” McCown told me. “It’s the end user, building inspector, or designer of the structure who must determine which AWPA use category should be specified.”

The three major wood treaters are divided on this issue. According to Fields, Viance will continue to recommend and warrant all of its UC3B products for deck framing when used appropriately in above-ground code-compliant applications. That’s not the case for Arch Wood Protection, manufacturer of Wolmanized products. Juliana Rumbaugh, marketing communications manager at Arch, told me that the company is recommending—and requiring for coverage under its warranty—UC4A treatment for lumber used for deck joists, ledgers, and support beams in most applications. Koppers (formerly Osmose) is taking a similar position, though senior vice president Gary Converse told me that its current warranty still applies to UC3B material that’s used for beams and joists. However, he also noted that the company is expecting to release an updated warranty next year to reflect the changes in the new standard.

Practically speaking, I think the lumber dealers are the ones who are going to figure this out. Many of them have already made it clear that they aren’t interested in carrying both UC3B and UC4A framing lumber, so it will be interesting to see what kind of PT framing lumber deck builders find at their local lumberyards in the coming months. I suspect that most of you will soon be paying a bit more for deck-framing materials.

Andrew Wormer