How durable is ground contact treated lumber?

Old 08-08-16, 08:31 AM
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How durable is ground contact treated lumber?

I guess, title says it all.
Reason being, I have very long wood fence, metal mesh and 3 horizontal 2x6 boards with 6x6 posts.
All lumber is clearly treated and posts have some sort of white additional treatment where they are inserted into concrete. It appears to be treatment as line across posts base is too straight to be natural.
But! In some areas, the bottom boards are more or less in the dirt.
As there is no labeling left on the boards, but wood clearly oozes out some sort of dark orange pigment, let's presume all lumber is ground contact grade.
So how long will it last when actually IN the ground? I am finishing re-sealing project for what's above the ground, but clearing those boards that are covered in dirt will take another month and I sort of have better things to do.
Not trying to cheat my way out but don't really want to do unnecessary work either.
Fence is about 8-9 yrs old. It's all in perfect condition, some darkening observed on some boards, hence re-sealing.
Old 08-08-16, 08:45 AM
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Old treated lumber back when they used arsenic could survive quite a long time in the ground. The newer treatments from what I've seen don't work nearly as well. I have CCA treated 4x4 posts in the ground that were set in 2002 and are still quite solid while I've already had to replace posts set in 2006 and 2008. The exact time your wood will survive depends too much on the wood and local conditions for any of us to guess how long your wood will last.
Old 08-08-16, 08:47 AM
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A lot depends on the ground both how wet [or often] it gets and insect activity.
Except for 4x4s, 6x6s and such most PT lumber is not rated for ground contact. Generally any PT lumber other than posts is not rated for ground contact. It is available but costs more and often has to be special ordered.
Old 08-08-16, 08:56 AM
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What is PT lumber? I got it. Pressure Treated.
Not to argue, but I saw 6x2 and 10x2 and 12x2 GC rated. That's how I found about that grading. As I have to replace a 2x12 on my balcony that rot through. But this is other story.
Wet and insects? It's PacNW. It IS wet and ants are all over the bottom boards.
Guy apparently spared no money to build this fence, so I am not sure how fancy this lumber is. Is there any way to actually scope if it is that grade or not? Like I said, it clearly is not natural treated lumber color. It's orange and has, in some areas, like dark orange crystals seeping out. What makes me believe - maybe it's just hope - that it was copper treated.
Entire reason I started resealing it was that I saw that pigmentation pealing off in some areas. Will cost me a lot of money to replace rotten boards, I'd rather have it resealed.
But digging out buried boards is a whole new task. Not all of them are, but some are part way, some half way, some entirely.

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