– By Sharon Thatcher, Rural Builder Magazine –
Colin McCown, Executive Vice President of AWPA (American Wood Protection Association), cautions against assuming that all treated wood you purchase off the shelf is suitable for ground contact applications. A particular problem is that most 2×4, 6, -8, -10 and -12 lumber is treated for above ground use, but contractors and consumers often use this material in ground contact. This is a misuse and results in a shortened useful life of that lumber.
When in doubt, read the label on the end of the lumber and ask questions from the supplier if you need preservative-treated wood treated for specific conditions. A special order may be necessary to obtain 2-inch dimension lumber treated for ground contact applications.
Another issue may arise when wood treated for above ground use is placed very close to the ground or is wetted frequently. To address this common problem, the AWPA is looking to adjust use category descriptions, in particular for category 3B of the AWPA standards. Changes may come in mid 2016.
Guidelines for what treated woods are to be used for specific conditions can be obtained from the AWPA website: awpa.com.