treated post on deck contacting ground

Have always written up post that are in contact with soil as piers are typically too low and when they back fill the body and piers are covered.
Builder calls me today and tells me he has a letter from the MFG stating that the treated post can be in contact with the soil and wants me to concur as to the letter making this ok.
I still contend that water will collect around base on top of piers buried and can over time rot the wood.
What say you experienced folks

Are they piers or did they just concrete in the posts like they do here? Neighbor had a PT 6x6 completely rot out after 3 years. Right at the top of the concrete and buried by a couple inches of soil. My next fence posts will be installed using these.

How long will it last… it all depends.

The chemical has become expensive… I was told that some companies do not treat like they used to… and 4X4 and 6X6 may be treated heavier than 2X4 or 2X6 boards as the boards are not typically expected to have ground contact. But yes they are supposed to be rated for direct contact with ground (the 4X4 and 6X6 may be all depending upon who treated them from what I was told).

I have a brother in law who has photos of poles pulled treated with pressure treating (CCA) that were in the ground for over 50 years… and are as good as the day they were placed. (they have date nails on the poles to know when placed) I will see if he can send me some pics.

Likely better if on concrete piers which extend above ground, but they are not going to rot away any time soon. Having said that, some are suggesting life span of pressure treated wood as 20 years… I have seen others say 20-30 years. But on other hand cedar is only going to be about 20 years likely as well.

Looks like nice device.

But rotting after two or three years… something is wrong with the material treatment. Now I suspect the utility companies pay more for better treatment… but theirs last decades.

He likely would have been better to either not bury, or to bury much deeper. I know on farm when growing up… we had cedar posts. The lower portion would never rot… the only part that rotted was right at surface (where soil met air). I suspect sides of the PT wood we buy is treated better than cut end… so if it is going to rot the cut end is likely the weak spot.

I have a little over 400 fence posts that I installed 25 years ago. Only 3 have rotted. I didn’t use concrete at any of them. Just added a little gravel mix to the native soil. And we are WET up here. Now that I am changing fence lines, new posts will be going in.

With all this said, and a MFG letter that the post are made for direct contact with the soil, do I hear collectively that I can’t dispute the MFG application BUT would still contend that as an inspector my observation was that post in contact with the soil (not sure if in poured concrete or sitting on piers as they are covered) is something to consider and that these have been known to fail, as I have personally seen post rotten at the bottoms of older decks.
Need to call builder and while I would not dispute his letter, I feel I should stick to my observation and let the client decide

I do not disagree with your thoughts, while they should be ok… depending upon how deep they are buried… they may not be optimal. Do not require changing… just inform client that they may have premature decay and shortened lifespan. Do not suggest that they will fail, or are installed incorrectly. You can not see what is below ground, so are basing on only what you can see.

What ones sees is the only thing one can report.
Below ground …Huh!
And really ! Just because there are green don’t mean they are designed to be sub surface…Correct?

One really needs to know the retention value to know what is going on.

Ground contact lumber incased in concrete as mentioned, has never been a good scenario.
Post for ground contact should be at the minimum of .4 and even better .6.

The life of each piece of wood will vary, depending on exactly where it came from within the tree, which has a direct effect on how well it accepts the treatment. I have seen PT wood rot in less than 2 years, and other materials that lasted more than 15.

For material that will last the longest, find a supplier that can provide you with material treated to .60 retention rate. This is the standard for marine usage, and while it will be expensive to purchase, factor in the labor cost a few years down the road to remove and replace what you built the first time.

Chart listed here;

I agree , but beyond the scope…Correct?

For sure beyond scope.

:)I guess. :wink:

Good info. Surprised CCA is not listed… but maybe is not available to homeowners. It is what utility wood is treated with, worked with it quite a bit in the 1970’s… 40 or 50 years in the ground and as good as the day it was placed. However, pressure used is likely a factor in treatment as well.

Having said that while CCA is still used, the treatment process has stricter rules to follow I think… so that may also be limiting factor in availability.

I have some CCA treated fence posts (old utility poles) which in their second life were placed maybe in 1977 or so and still in ground with as far as I know no issues.

This is the comment I use for post mentioned
"[Post contact with soil]]One or more posts which support the deck had contact with soil at the time of the inspection.
Wood in contact with soil will eventually decay, the decayed area will crush under the weight of the load it supports and the deck will lose support in the area of any affected posts. This condition may eventually result in damage to the deck or the development of unsafe structural conditions.
The Inspector recommends that all posts supporting the deck be protected form contact with soil.

Anyone else mention anything like this when post are contacting soil? If no why not?
Seems the info you guys all provided supports mentioning this condition.
If owner understands that leaving it alone may or may not create an issue down the road have we not done our diligence ?
I don’t have the answer just looking at consensus

If a treated post contacts the soil, I check for decay. If none, then nothing to report.

I have through my years, have found decay and termites in treated lumber.

You have any technical data?
It would be much appreciated.

Thanks as always!

Good thread GeorgeI Hope it gets legs!

If it’s rated for direct contact, then its OK. Yes, it will eventually fail but it will take more than 15 years most likely. The entire deck will someday have to be replaced! Even the pyramids wear out. Nothing lasts forever.

Check the post no rot . Mention it may deteriorate faster than if it was not in contact , soil conditions lumber treatment may vary as mentioned CYA

:mrgreen::mrgreen:The bigger question is how the ledger is attached to the home. Ron should be along shortly. LOL