The American Wood Protection Association will be issuing its new standard for U1 preservative-treated lumber in May or June of this year. The new standard will require many joists, beams, and ledgers to be treated for ground contact. Though the rule hasn't been published, many dealers are already switching over their inventories to ground-contact PT lumber. In writing for ProSales' sister publication, Professional Deck Builder, editor Andrew Wormer outlines some of the confusion with the new rule:
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?
To read Wormer's full editorial, follow the link below