Hi all. I'm curious about what level of CCA concentration you use for barn poles. Everything I've read says that for structural poles it should be at least .60. I've asked at the local home centers (Lowe's, Home Depot, 84 Lumber) about availability of .60 treated material and they look at me like I have a third eye in the middle of my forehead.
First of all CCA treated poles are rapidly becoming extinct. Most lumberyards are switching over to other treatments because of the arsenic in the CCA treated materials. If you are using 4x4" poles, they come in .40 or .60 but if you are using 4x6" or larger they only come in the .60 (or maybe higher). My local building codes require the .60 treated lumber but I was using all 4x6" and 6x6" so it didn't really matter.
I had the exact same experience at HD. They were clueless about treated posts. Try finding a lumber yard that sells pole barn kits, or at least metal siding. They will know about treated posts.
I would look into the laminated post used for pole barns. They a stronger, straighter, and more dimensionally stable than solid posts. They are only treated on the lower 4-6', which is great. No use treating areas that don't require it. .6 should be sufficient for ground contact. I have seen the laminated posts treated to .8 (marine grade). That’ll last you forever.
I think CCA is still approved for ground contact use. I think the new treatment doesn’t work as well in that respect. I think they are mainly trying to eliminate CCA use in home decking and playsets.
BTW, there is a good thread over on tractorbynet.com about pole barns that has been going on for the last week in the projects forum.
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