question about posts for pole building

[Qweaver]

Concrete around a post is a bad idea.  Concrete holds water.  When I inspected utility poles, those with concrete around them were more prone to rot.

The butts on treated posts are usually treated heavier than the rest of the pole.  Your results may vary as you go up the pole.

Redbeard's is similar to what we used on our mill.  I also like Larry's idea with the 2x6s.

Not to be contrary, but I have found this not to be true.  When hurricane Ike destroyed my outbuildings and rent house, I pulled all of the 20 year old concreted treated wood posts and knocked off the concrete.  The posts were as solid as the day I put them in the ground and I have reused them.  This was in south Texas on the bay where everything rots.  One of the things to do is to not concrete under the post.  Leave the bottom open so that moisture can escape.  I concrete all of my posts and have never had a rot problem!  The tops may decay if they are not capped.

[Raider Bill]

I concreted all of my 4x4 treated fence posts [658 ft of 6' stockade fence with a post every 8']. Left the bottoms open. Every single one rotted and broke off at the top.
We have very sandy soil [florida].

[Qweaver]

It's amazing that we would have such opposite experiences.  But if the posts are failing at the soil line,  would the same thing happen without concrete?  I don't know because I have always concreted them.  I had never pulled a post before the hurricane forced me to do it and I did not have a single rotted post.  All of my house and seven sheds are concreted and none show any sign of decay...but they have only been in for 6 years max.  The posts in my bay front house in Texas showed a lot of decay at ground level and they were not concreted.  But they were put in in the 50s.

[Raider Bill]

I think I put them in around late 96-97. When I concreted them several people thought I was nuts. Me trying to do things the permanent way and making up for lack of knowledge and skill [if 4 nails are good 8 should be better thought process] put 2 bags in each hole and thought they were nuts to have not used concrete.  :D

The panels are only going to last another 2-3 years at best anyway.

[Ga Mtn Man]

Perhaps the quality of the treated lumber varies from region to region or even from producer to producer. ???

[beenthere]

There are different levels of treatments.
But never figured it was a good idea to encase the treated wood in concrete.

It shortens the life of the wood, regardless. But short term is long enough for some so if ya like 'em in concrete, enjoy.  ;D

[ancjr]

I worked on a farm with several barns, all of which were at least 70 years old.  The one that was in the best condition had posts set in 12" concrete piers which were about 8ft tall.  The bottom 4 feet were below grade, and 4ft above grade. 

I forget if the posts were set into or bolted to the piers, but I know that bumping one with a vehicle or tractor wouldn't have damaged much other than the vehicle. 

Groundhogs had dug around the posts of the previous barn to the point it caused it to collapse, and the fella that ran the place at the time was into some serious over-engineering if it meant something only had to be done once in his lifetime.

[Raider Bill]

The only thing I could figure is that water sat on the concrete and worked it's way into the wood although some were flush and some were under the sand some it just  depended on how aggressive we were with the post hole diggers along the sides.
It was all Orange store PT.

What do you cap the tops with?

[Qweaver]

There are different levels of treatments.
But never figured it was a good idea to encase the treated wood in concrete.

It shortens the life of the wood, regardless. But short term is long enough for some so if ya like 'em in concrete, enjoy.  ;D

Well...I've tried to research this and I find as many for as there is against.  My personal experience with actually pulling the posts and busting off the concrete is pretty hard to argue against.  Also I have several instances right here and also in Texas where un-concreted posts have rotted.  I think that posts rotting at the dirt level can occur in both cases.  As far as being "Short Term"  The posts that I pulled in Texas had been in well over 15 years with no rot at all.
So I think it is un-founded to say that concrete causes posts to rot.  Can the posts rot above the concrete?  I'd say yes...but so can a post packed with dirt.  I've got several examples of that right here.

[Raider Bill]

I wonder if it has anything to do with soil, rain, water table in ground etc? I dunno... could be one of those ford / Chevy things. ;)

[hackberry jake]

The things that cause rot (bacteria, fungus, etc) all need air, water, and food. The wood is the food so unless you use steel or concrete posts you cant cut them off from food. Treatment makes the food poisonous to them. It is very hard to cut them off from water unless it never rains where you are. You can minimize how much water the posts see by not putting them in the ground, or putting gravel around the post for drainage. The air is scarce below ground level and the water is scarce above. For those that want to put posts in concrete for strength, you might try putting a few inches of concrete around the post about a foot above ground level. This would not only keep air away from the post but also keep standing water from running into your post hole. The old chicken houses around here were built like MReinemann did. And most of them are 60-70 years old and still standing.

[grweldon]

I read with concern the messages about posts rotting while encased in concrete.  That is exactly what I did for my house in 2007.  They were exposed to the weather for at least 12 months before I got a roof on over them and protected them from the weather.  Some of them were added after the roof was on and have never seen water around them being under the house.  The posts on the edges are still exposed to water splash, but the concrete was formed around the top and doesn't allow water to pool around the posts.



I've always thought of them as semi-permanent, thinking I would eventually dig out the basement and support the house with a block foundation, but that may never happen.  If they all rot equally (assuming they WILL rot), I could find that during a heavy windstorm, the house just falls off and sits itself on the hill it's built on!

Since I can't do anything about it at the moment (or choose not to) what do you think might be the best way to check for continued post integrity?

[beenthere]

As mentioned earlier, there are different PT retention levels that can effect the longevity of posts in the ground, as well as posts set in concrete.
http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2531/NREM-5047web%20color.pdf

I've no problem with anyone setting their posts in concrete... just IMO they will fare less well compared to not setting them in concrete.

When I put 6x6 treated posts in the ground for my shed 40 years ago, the posts are still in good shape. If I'd set them in concrete, I'd have likely already had to replace them by now and it would have been a real PIT tush.

Our local town ball diamond that had 7 wood light poles put up (donated money and donated labor to set the poles), they were in concrete and one night after just 7 years when one fell over. Checked the rest of them and they were but just a thin shell of sound wood. Closed the ball diamond and eventually removed the remaining posts and they were soaking wet below the ground line (and rotten). Concrete won't seal around the wood. Water will run down the wood and behind the concrete.

If set in concrete, be a good idea to have the marine levels of treatment retention.

[Ianab]

What's commonly done here is that you pour a concrete footer into the bottom of the hole, for the post to sit on. Then fill the hole with packed dirt, and pour about a 6" concrete "ring" to hold the top of the post in place.

Because most of the post is just in dirt it's able to drain, and any water that seeps down the sides of the post can drain through the ring and away.

Even treated posts don't last a long time if they are sitting in a concrete puddle, and while 20 years sounds like a long time, it's less than you would expect a shed to last.

Ian

[hackberry jake]

I am a habitual over builder. I cant stand thinking that my work wont outlast me (27). So I try to overbuild everything and it has payed off so far. Keep your posts above ground level unless its a temporary building.