Hi Team,
I have been doing a lot more new construction inspections lately. 99% of the decks have the wood support post in contact with the soil. Of course the deck is new so there is no damage from prolonged exposure to moisture but I still make a note that even treated lumber will degrade when exposed to moisture for a long period of time. Just curious if inspectors in other areas are seeing this too?
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All the time!
How would we know, as you don’t have a Signature listed, so we don’t know what area you are located in?
If the deck is attached to the house then all support columns require footings below frost line or 12 inches, whichever is deeper. Free standing decks don’t require footings.
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It is permitted in GA, depending on the wood rating and soils. ^^^^^^^^
I call it out when I see moisture wicking with wood deterioration. I also note my limitation (I can’t see what is buried)
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There are different classifications of treated lumber, ground contact being the one you want for buried posts. When I was building, we paid attention to the retention level, either 0.4 or 0.6. 6 x 6 posts supplied locally were 0.6 and 4 x 4 posts were 0.4. Whenever I see 4 x 4 posts used for support, I always probe with an awl, looking for rot. My rule is 6 x 6 posts are fine for direct bury and 4 x 4 posts are not. However, lumber brought to my area from big box stores can be an exception to this rule.
Unless the label is still on the timber, you don’t know what the retention level is. Thus you don’t know if it is approved for direct ground contact or not. See Treated Lumber Classifications for detailed information about the label.
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As an addition to the above, wood foundations use 0.6 treated wood. I used to subcontract wood foundations to a company specializing in that work. They offer a 75 year rot replacement warranty. Buried treated wood can have a long service life, so long as the proper level of treatment is present.
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Thank you for sharing your knowledge and experience. I will keep this in consideration and do some research to better understand the difference. Your input was very much appreciated!
That’s my approach as well. Thank you responding and sharing your experience
If you probed it and see no deterioration or any other visible signs of failure then there is nothing to write up. 99% of posts around my area are buried, even new construction. Sometimes even the few posts that have post bases installed on new construction get buried after the grading guy is done.
Now, that doesn’t mean there aren’t exceptions. I had a 4 year old house that I inspected late last year that had one 6x6 rotted to the core. All of the other 6x6s were fine. I had a house a few years ago that was less than 10 years old at the time and most of the 4x4s are rotted through. Sometimes the wood doesn’t get treated properly or doesn’t retain the chemicals properly or have some other defect.
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