Deck posts

Have a question concerning deck posts and contact with soil. Is it ok for deck posts (even treated ones ) to be in contact with soil? My report system says no soil contact, but I look at NACHI graphics and they often show the posts going into soil and resting on footings. They also say no soil contact, above ground with pier or post footings with anchors. Whats up? I’m in MN so maybe our codes are different.

It is allowed if it is suitable for that purpose…

From the 2006 IRC.
**- **R319.1.2 Ground contact. All wood in contact with the ground, embedded in concrete in direct contact with the ground or embedded in concrete exposed to the weather that supports permanent structures intended for human occupancy shall be approved pressure-preservative-treated wood suitable for ground contact use, except untreated wood may be used where entirely below groundwater level or continuously submerged in fresh water.

…and look at the minimum requirements in this document:

If you visit a lumber yard near a large lake area, you can usually find pressure treated lumber that is “double treated” for dock construction, etc… So like Larry mentioned, check to see if you can locate the “ground contact” stamp on the lumber.

I’d have to write up 99.9% of every deck I inspected if ground contact was not OK.

Thanks guys, sometimes there’s to much information out there.

Like was mentioned, go to lumber yard and look at the stamp.
4"x4" and bigger have stamps that say .40 retention suitable for ground contact. Most others will be like .25 retention suitable for above grade.

For waterborne preservatives, the following levels of preservative retention applies**: **0.25 (lbs./ft³) – this is the minimum level for low exposure above ground contact elements; .40 – for ground contact elements such as fence posts and deck supports; and, 0.60 – for permanent ground burial such as wood foundations.

While it is acceptable it is not practical. The best way to install deck post is to set it upon a gravel base at least 6-12 inches thick and is so desired poured concrete / sacrete around same, this gives stability while preventing the post from wicking moisture, in addition to that I have my framers wrap 30# felt around post; with that said, I would not write it up since it does meet code and no safety issues are at hand.

And I agree with Joe, rarely do I come across a deck that does not have several deficiencies.

At one time many of the PT lumber manufacturers only warranted their products for 5 years…that speaks for itself.


Agreed. But this how inspectors get into trouble too. The wood posts in direct contact with soil are either a defect or they’re not. At least that’s how I interpret CYA report writing. :wink:

Nice response Erol, I tend to agree with you. I did have to google CYA to find out what it stood for. Once I did it made even more sense, thanks for checking in.