Is concrete really necessary for fence? in CA?

[bloozman]

I was delighted to see this Forum. I am hoping someone can help offer some real insight into this debate I am having. I'd like to hear some real experiences and not just opinion and tradition on this issue, if possible and please try to keep an open mind.

It seems that nearly every construction guy and every fence construction guy thinks I am "crazy not to use concrete" because I don't want concrete necessarily holding my fence posts up. While I admit that in the San Francisco Bay Area, where I now live, we have a lot of clay and during the rainy season it gets pretty mushy and spongy out there in the yard, I know that on the East Coast, where I am originally from, it was unnecessary, however. Many of you East Coast construction guys may think that it's even required out there, and you also may call me crazy, but my father who was in construction called it "suburban overkill" to use concrete bases for fences. We never did and I put up fence with him. My brother recently replaced that fence, which lasted 30 years and he did not use concrete either. We used gravel and rocks around the post, which I have read online from at least one other non-conformist fence man who claims that approach provides better drainage than the concrete. My father's attitude was never to use a permanent foundation for an impermanent (non-permanent) structure. Fencing is an impermanent structure. However, maybe in this soil, the concrete might be more necessary, and that's why I am writing to you all. A lot of guys who tell me that concrete's necessary have never done it or seen it done any other way, though. They seem to simply be following tradition. We did uncover that concrete post foundations were not part of the code requirements out here, either. It was suggested to go deeper with the posts if not using concrete. So if it is not part of the code, then is it really necessary? How much does it help if at all? I can tell you why I am skeptical.

A section of my home's fence, which was put up using concrete out here in "The Bay Area" California by the previous owner, collapsed last summer, and, again, it had concrete under it. The fact is that a post still rotted out and the fence collapsed -- not even during a storm or anything. I don't know exactly how old the fence is, but I have only been here ten years. I think maybe it was fifteen years old or less. I have heard it described online that the concrete fails because after it hardens, it shrinks, and so there is still space around the post between the concrete and the post and water gets in there and can essentially soak the fence posts underground. In a way concrete traps the water against the post inside the concrete in a worse fashion when concrete is used. One "expert" out here suggested we make sure there is at least six to eight inches of drainage gravel under the concrete to remedy this. I agree that if we need concrete this would be wise.

I am wondering why use the dang concrete at all?? When the posts rot and the fence fails and eventually it will in my opinion, now one has to dig out all the dang concrete on top of replacing the post. I know this firsthand now. I put up that section of fence without the concrete and lo and behold it survived one rainy season (winter).

(2) If you will allow me a second question, do you think a pressure(chemical)-treated post, which is usually typical pine is any better than taking a harder redwood post and chemically treating the bottom with that copper green stuff, which I think is the same stuff they use in pressure-treating, but obviously without the pressure part of it?

Am I as insane a skeptic as the experienced construction guys claim and/or is it that the California soil is worse in holding up fence posts than my Long Island home or is that in California the suburban overkill has now taken over in a herd mentality with the younger generation (than my Dad's) to the point where no other approaches can be reasonably considered?

I would love for the experts to weigh in, here, and if there are a few guys out there who have done it both ways and seen the non-concrete approach fail faster, then how much faster did they fail? Because it's a lot easier to repair it without having to dig up concrete! I would especially appreciate experience in favor of opinion, but I guess opinions alone are welcome too. If I may be so bold, please let me know your firsthand experience levels with this issue. This should be an interesting debate, no?

Thanks in advance,

Bloozman

[concretemasonry]

You made a long post for a short question.

Concrete is used to provide a wider base for the fence post stability when the soil is not good enough or you do not want to rely on unpredictable compaction of the questionable backfill around a post.

If you have a corner post or an end post at a gate, concrete is really a great choice because of the strength and stability. - Mis-aligned gates are a pain and ugly.

If you have a wire or split rail fence, you can get away without concrete if the soil and backfill is good enough. If you have a 6' or 8' privacy fence, that is a different question, but high winds in some coastal areas my require concrete or something better than dirt to keep vertical.

When you are building a "straight" fence, you can get very sloppy. since you are not building a "piano".

Concrete does not make wood rot. Rotting is from changes in moisture that are most common where the wood goes through alternate cycles of wetting and drying that happen when the post is exposed at grade or at varying sea levels, such as piers and piling.

If you used concrete as a base to increase the strength of a post, make sure it is slightly above grade with a slope to shed water away from the wood and protect it. If you have a real problem, use either steel or concrete posts.

Not using concrete is definitely cheaper and faster if that is your aim.

Dick

[bloozman]

Thanks for the reply, Concretemasonry. I left the lengthy post to tease out many of the issues that have been discussed or described so far. I did not want the answers to point out the obvious or already known.

It is a wide or large-picket, wooden privacy fence 8' high, and we might want to make it a touch higher, if permitted.

I almost mentioned that I learned if concrete is used, that the concrete base crown should come up above the ground (or grade) a few inches with a slope to make sure the water rolls off the top of the concrete and away from the post, to help prevent rotting, but then my post would have been EVEN LONGER!

While The Bay Area sports some significant average windspeed (which is why it is one of the country's top windsurfing spots), I am inland enough from the coast, that it's no beach house. I am a good 15 minutes from Half Moon Bay, for example and that's with no traffic. It is the San Francisco Peninsula, though.

It is interesting that you say it is faster and cheaper to forgo concrete, because the fence construction guys want to charge more because of "increased labor" for packing in gravel and rocks around the post rather than just dropping in the concrete. I agree, that not having to mix and set concrete should easily offset packing in rocks and gravel. I don't think any extra labor charge is necessary at all.

I am also well aware that concrete does not rot the post, but that water along with bacteria, termites and other wood-eating organisms does the trick over time. However, if concrete helps to trap the water in like I described, it could most definitely be a factor.

I do very much appreciate the feedback.

[Rich]

Just pound pressure treated posts in. I put up some fence like that when I was a kid 18 some years ago and it's still standing strong. The rails have been replaced twice but the posts are still there. I've also augered PT posts in with little to no trouble with stability. About the only time I've seen concrete used in MT is with steel round posts or when the ground is just too rocky (large rocks) to provide stability. The soil around here is pretty good though.

[Don_P]

For ag fencing here it is rocks and dirt with black locust posts. Locust is in the same durability class as redwood. In testing 10-15 years is about average before the soil borne enzyme cellulase breaks the wood down. Notice guard rails and many other posts are in direct ground contact. Fencing contractors in a couple of articles I looked up do feel concrete helps them last longer IF it is brought up above grade and domed as Dick suggests. I think a well tamped post takes longer than a couple of sacks. A pounded post is pretty quick. Well, till you hit the roots of the mountain.

[bloozman]

Guys,

I very much appreciate the feedback. It is sort of confirming most of what I suspected, which is that the concrete might help only a little in durability, if that, and that 10 - 15 years is the true lifespan. I'd be willing to trade any extra in durability for the ease of replacing posts with no concrete.

I am still looking for more insight into the necessity of the concrete to hold the fence up -- prevent it from collapsing prematurely in the clay mushy soil during the rainy season here in Central Coast California.

My feeling is that if the soil becomes so mushy that deeply dug, placed and rock-gravel-packed fence posts would lean over, then why would the concrete block not lean, as well, causing the fence to also lean or collapse? I'm still not sold on the concrete necessity.

Don-P, any way to have you send me those article links? I read a few last year, but nothing too scientific or in-depth.

Anybody out there who knows California soil and environment, specifically?

Thanks to all who have contributed. It's just great stuff. Thanks, again.

[Mike44]

I'm not a fencing expert here or anything, but I just wanted to throw this idea out there. Don't take this as advice though, I'm just putting out an idea.

I read that you are concerned about rotting posts and the amount of labour it would take to replace them. In saying that, would Simpson Strong Ties for posts and columns be able to do the job? Here is a link to the pictures of the ones I am talking about: http://www.strongtie.com/products/highwind/PostColumnBases.html. I'm looking at the D67 or the D68. I'm not sure about this though - the reason being: are these only for vertical loads (from a deck structure) as opposed to horizontal loads (from wind pushing against the fence)?

If these cannot be used for fencing, I understand why, but I just thought about the benefits for your type of situation. One, the post would be elevated off of the ground level so that you do not have to worry about the damaging effects of the water and rot, and two, if the post did rot and you had to replace it, you would only have to remove the bolts, pop in a new post, and secure it back in place - no digging up the concrete.

So again, don't take this as advice from a pro, because I'm far from it! I'm learning here with you!

Mike

[bloozman]

Thanks Mike,

One of my other neighbors suggested a bolt idea. I did not know what types of bolts were feasible, so your link was very helpful.

That is also a bit of extra upfront work, but it likely does also solve the constant problem of avoiding having to regularly dig up concrete to replace/fix posts that rot or otherwise collapse.

That was a good suggestion, professional or not. Thanks

Joe

[Brentconstruction]

As mentioned in some of the replies, it's imperative that you consider the lumber that you are using. It is said that cedar should not be in direct contact with concrete, but you can get sleeves and then concrete them in. Also as mentioned, it's imperative that you consider the ground that you are working with. If it's sandy, forget about setting a solid post without and crete. If it was something like Georgia clay, it could be done and the post could last a lifetime, but it still would never be s strong as if it was set in a well "belled" hole with some high psi concrete.

AFA Certified Fence Professional
Atlanta, GA Fence
(http://www.productionfenceworks.com)

[handyman4life]

Depends on the soil and how much you are willing to dig.

[ctdecks]

i prefer to set a post in a bit of concrete, although it is very possible to get good results without concrete and by packing the soil carefullly around the posts. with concrete your sucess ratio is higher

paul
http://www.deckspecialists.com/

[workingman]

have you heard of OZ Post... i used this and found it on the Viking Fence Website. Has a cool demo..and it really works

[concretemasonry]

I think the OZ post was invented years ago by a Wizard in Australia. - So far its main success is for temporary Realtor signs. It is not adequate for anything permanent.

[ObeseSquirrel]

But I built my home out of OZ posts?!

jk