hausdok Posted December 10, 2009 Report Share Posted December 10, 2009 In another thread, I saw where one of the brethren told an inspector that all pressure-treated wood is designed for ground contact. That's a fallacy and is simply not true. Some pressure-treated wood that's designed for use in fences, balustrades and deck surfaces is not adequately treated for ground contact and should not be used in applications where it might come into contact with soil. Other pressure-treated wood is designed for ground contact and the choice of fastener is going to depend on whether it's going to constantly stay very wet or whether it's not expected to stay continuously wet and will dry out somewhat between wetting. Keep in mind that treatments don't always protect all of the wood anyway. When you cross-cut a piece of P.T. wood, you'll find that only about the outer 30 to 35% of the board is actually treated and that the rest at the core is untreated; so it will still absorb moisture and that moisture still cause it to eventually rot and become insect infested. Treating the end grain and waterproofing P.T. lumber will help to slow down degradation but it's still going to eventually rot, even if it never comes near soil. Sometimes it's possible during an inspection to know what concentration of preservative has been used. Just look for the tag left nailed to the end of the lumber. I find them all the time. Here's some helpful information I scarfed up from the Simpson site: For Above Ground use/exposures the following retentions are typical: (i.e. wood not in contact with soil) 0.25 pcf for ACQ, CCA-C, MCQ 0.20 pcf for CBA-A 0.10 pcf for CA-B For Ground Contact use / exposures the following retentions are typical: (i.e. wood in contact with soil) 0.40 pcf for ACQ, CCA-C, MCQ 0.41 pcf for CBA-A 0.21 pcf for CA-B For wood with actual retention levels greater than 0.40 pcf for ACQ MCQ, 0.41 pcf for CBA-A, or 0.21 pcf for CA-B (Ground Contact), Stainless Steel connectors and fasteners are recommended. Verify actual retention level with the wood treater. To read an excellent FAQ section about P.T. wood on the Simpson site, click here. ONE TEAM - ONE FIGHT!!! Mike Quote Link to comment Share on other sites More sharing options...
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