The American Wood Protection Association (AWPA) is about to publish an update to its U1 standard for preservative-treated lumber. When the new standard is published as part of the AWPA’s 2016 Book of Standards (probably in May or June), all deck framing lumber, including posts, beams, and joists, will have to be treated to the AWPA’s UC4A Ground Contact preservative retention levels.
KOPPERS WEBSITE HAS A GREAT EXPLANATION OF WHAT THESE CHANGES ENTAIL.
http://www.kopperspc.com/pressroom/awpa-new-change.html