As part of our review, we ended up making some changes to our Corrosion Resistance Classifications, which we cover here.

When builders specify treated wood, the standard that defines the appropriate treatment chemicals and chemical retention are contained in an American Wood Protection Association standard called AWPA U1-15. This is summarized in a Use Category system in which chemical retention increases as the UC rating increases.

But the AWPA UC system does not include environmental corrosion agents, so we had to separately integrate those with treatment chemical effects as we developed the classifications.