6x6 treated posts in ground

[tractorgp]

In this video I'm repairing one of my high back chairs. Two of the three legs had rot at ground level and snapped off in high winds. I had to cut the third leg. When I dug down to remove the buried part of the legs and cross members I also found a fair amount of rot (3:20 in the video shows this). The chairs were installed about 8 years ago and I picked up the CCA 4x4's at a home center. Don't have any other details on the level of treatment etc. I live in a damp climate.
(Posted this video some time ago on TBN so just putting a link to it here.)

High back chair repair Kubota BX big player - YouTube

 

[PeterK]

The treated lumber that is sold here has a label which states 'Not for direct ground contact" which I always thought was kind of odd. So as far as sinking it in the ground without additional protection might be problematic in the long run.

What I've started to do is spray then bottom ends of any outdoor wood (even metal fence posts) with truck bed liner for the length under and near under the ground. Cheap insurance. Just my 2 cents though.

 

[TemporaryKubotaOwnerMark]

Concrete increases decay by trapping water.

Educate me on this. I'm willing to learn something new.

Lots of reading available.

Concrete increases wooden post decay by trapping water. at DuckDuckGo

 

[jimmysisson]

If these are for a building, where there interior faces, you can drill a hole down at 45* just above grade and squirt thin oil into it every so often. Or do that on the outsides, where the rot starts. That small amt if oil will not escape into the ground. Posts only really rot in the top 8" below grade. Concreting around them won't help with that. Agreed w the "below ground contact" grades. I would not be afraid to expect 40-50 years if the sun is kept off the post.
Jim

 

[joecoin]

Use Osage Orange for posts.

 

[RNeumann]

Lots of reading available.

Concrete increases wooden post decay by trapping water. at DuckDuckGo

Double tap this- concrete should be thought of as a sponge. If you insist on putting wood in the ground the goal is to keep it dry. Second best is to provide excellent drainage- stone and or crushed stone works.

 

[crazyal]

Finding PT 4x4 posts around here isn't easy. Most everything is for above ground use. OTOH the 6x6 posts are landscaping timbers designed to be for ground contact. Ground contact doesn't mean burying but will last longer than those designed for above ground use. Back in the day I would just say get some creosote and brush on a nice heavy cote but the EPA has ruled it out. I had access to old telephone poles but now the EPA makes power companies treat them like toxic waste so they don't give them away anymore.

 

[TemporaryKubotaOwnerMark]

Use Osage Orange for posts.

Also called "hedge", correct? I have heard that that stuff is nearly indestructible. But, not all of us can get it. We have a bit of it where I live, but it's not plentiful enough to use for any large projects.

Double tap this- concrete should be thought of as a sponge. If you insist on putting wood in the ground the goal is to keep it dry. Second best is to provide excellent drainage- stone and or crushed stone works.

Yes, I have wondered if it would be worth the time to auger down about 3 or 4 feet, fill with crushed stone to the level where the post sits, then tamp in dirt to hold the post. It would provide good drainage for the post, I think.

 

[s219]

Yes, I have wondered if it would be worth the time to auger down about 3 or 4 feet, fill with crushed stone to the level where the post sits, then tamp in dirt to hold the post. It would provide good drainage for the post, I think.

The real answer depends on the soil and the size of footings required for the design roof loads. When my barn was planned out, roof loads were computed down to the footing requirements on each post, and that dictated the required pre-cast cookie footer size as well as the requirement to bore down to undisturbed soil. Then, for shear loads, holes were required to be back filled with dry concrete mix, as the spoils from digging the holes would not have provided sufficient resistance to keep a pole from going over with a wind load on a wall. There was a lot more to it than I expected.

For decks, where these requirements are not an issue, many people will rest the post on a concrete footer in the ground and then backfill the hole with pea gravel or a fine #8 gravel. I haven't ever tried that but I hear it works well and helps the post last a lot longer.

 

[EddieWalker]

I think most people confuse what they have seen happen to fence posts and assume that the same thing is happening to deck posts or pole barn posts. In 100% of the time where I've come across a rotted post, it's rotted away at ground level, and the ground is lower around the post then anywhere else. Water sits there longer. For wood to rot, it has to go from wet to dry many many times. If you build up the area around a post so that water runs away from it, that post will last for many decades. 30 to 100 years depending on all the other factors that it has to deal with. If you put a roof over that post and cover it with a wall and the ground slopes away from the building, that wood post will easily last 100 years.