I inspected a house yesterday that had extensive use of pressure treated lumber in the crawl space. It was non structural, but used to as retaining wall. Hard to explain in a sentance or two. My??? is should this be called out as condusive condition? There were no pest that I observed. But of coarse the wood was very damp and buried in the soil. Thanks for any input.
Any lumber, treated or not, will deteriorate over time when in contact with soil. Recommend replace with stone/concrete. Inform, document, done.
Craig
The amount of preservative in the lumber determines if ground contact is permissible. Most post material 4x4 & 6x6 are permitted to be placed in contact with the soil. Most 2x lumber is not. See The attached report for more information.
Craig,
Here is a link to the AWPA with more information http://www.awpa.com/references/homeowner.asp
Craig,
Attached is the standard AWPA uses to grade treated lumber.
Good info. Mr Mayo !
So what about wood foundations? do you call those up as defective because they touch the soil??
Actually Greg if you look into the design of the pressure treated foundation they do not touch ground but are in contact with concrete continuos footings at least the ones I have inspected.
Good point Greg, wood foundations date back to the 70’s I believe, in Canada.
It is all about the retention and type of treatment as Mr. Mayo posted. 
I agree that a retaining wall would be something I would call out if it did not have a runner or footing.
I should add depending on what the retaining wall is being used for.
Perhaps it has to do with climate. Here in Kansas, HI laws require us to document any wood that is in contact with the soil in any home. I have seen many landscape and retention treated lumber that has rotted, and became termite infested.
That is also in the WDO course also of NY.
Gary
If you look at the attached termite map the northern climates have little or no termites. The cold winters and frost depth is not health for a termite. That’s why most wooden foundations are typically limited to these termite free areas.
Don’t know why pressure treated lumber with a retention of .4 can’t be used for ground contact in Kansas.
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7415.html
Pressure-treated lumber is toxic to termites and discourages new kings and queens from establishing colonies in it. If susceptible wood is used above the treated wood, however, subterranean termites can build their shelter tubes over chemically treated wood and infest untreated wood above.
Use only “exterior grade” pressure-treated lumber for areas that are exposed to weather; otherwise the chemical in the lumber may leach from the wood. All topical treatments, especially borates, that will be exposed to weather, must also have a sealer coat to prevent leaching into the soil following rain. Because they contain pesticides, disposal of treated lumber requires special handling.
Once the end is cut then it is no longer treated. They also cannot penetrate very far into the wood with preservative so therefore any damage can be the start of WDO getting into the heart of the wood.
Most homes here are PWF. Wood does contact soil all the time. I had a source at one point that said the life span of a wood foundation has a lifespan of 75 years where a concrete foundation was 100. Alot of the homes are also built on a wood footing as well. The engineers actually preferred this as it allowed water to pass under the footing with little to no resistance. This keeps hydralic pressure from pushing the walls in. I have a booklet on them but am not about to scan the 40 pages and put it in. One thing to watch for is the end cuts as Kevin said. There should be a green paint (penta) on the ends. If it is not there it was not dipped or painted with preservative and considered defective.
Greg I was taught 50 years or half the life of concrete and no contact with soil on the supported walls without a sleeper on a gravel bed or concrete strip, also it is very important to watch out how they place is back filled. However like you say everything is different in each area you go. Since your area has more PT on ground they may have less restrictions.
I figured out where I saw the life span chart. It washere.
I have zero issues with PT touching the ground. We don’t have issues with WDO so maybe that is the differance. As long as the drainage system is adequite to remove excess moisture that is. A new system has come along in the last 5 years that seems to work better than weeping tile. 2 1/2" pipe is installed every 3 feet through the concrete footing. The earth is sloped towards the sump pit and pump. we have around 8" of rock in the basement and 16" on the exterior perimeter. I have not seen a flooded basement since this was started. The city now requires it as well.
Good to here they corrected that problem and 75 years is just a little hard for me to believe but we will be dead and gone to know for sure anyways.
For the CCA treated wood, the end cur treatment is copper napthenate (one brand is Cuprinol).