Earth to Wood Contact with Treated Lumber

Lately I’ve been answering calls on why I call out deck posts that are in contact with soil on my home inspections. As one homeowner pointed out, treated lumber is allowed to be used per the International Residential Code. To his surprise, I agreed. Specifically, R317.1.2 requires that wood with ground contact be treated but allows for ground contact and burial.

I still call it as an issue. The reason is pretty simple. I am required to by the State of Washington Standards of Practice. In WAC 308-408C-070 Structure, Section 1(b) states that the Inspector shall “Report all wood rot and pest-conducive conditions discovered.” The Standard is quite explicit. Regardless of functionality, I have to report it.

The argument against reporting is that the lumber is treated so not a conducive condition. Unfortunately, this doesn’t hold. Washington State has a legal definition for what constitutes a conducive condition. That definition can be found in WAC 16-228-2025 Conducive conditions. There are a whole slew of conditions listed. The one we need is at (2) Conducive conditions include, but are not limited to, the following: (a) Earth in direct contact with wood or inadequate clearance between earth and any wood or material subject to damage from moisture.”

Again, very clear. Note also, there is no exemption for treated lumber. I’ve had people suggest that I could probe below the surface and, if there is no wood destroying fungus (wood rot) present, sign off on it. Two problems – first, depending on burial depth, I might not be able to probe the entire piece. Second, the IRC, in the same section, R317, that allows ground contact, mandates in R317.1.1 that all “field-cut ends, notches, and drilled holes of preservative treated wood shall be treated in the field in accordance with AWPA M4.”

I have never seen any contractor field treat wood, period. If the deck post has been cut, we have an issue.

Earth to wood contact is always a reportable condition for a home inspection conducted to Washington SOP’s – as all within the state are required to be, despite the conflict with the IRC.