A recent storm (Zeta) broke three 4x4 fence supports because they were rotten at ground level and had no strength. I have no idea if the posts were pressure-treated or not. A guy who we might hire to replace them suggested anchoring them in concrete.
I'm looking for information and advice on this because it seems feasible that if treated posts were used, they could be expected to last at least five years without concrete. Is this true? In addition, when they DO need to be replaced again, it'll be way easier without having to dig up the old concrete plug. If someone here has experience relevant to this situation, I'm very interested in your thoughts about this.
I put in a couple hundred feet of 6ft fence using 4x4s. I also have experience repairing storm damage to that fence.
The 4x4 posts should be specifically rated to be put in the ground. Regular pressure treated is no good.
I set all of mine in concrete. I don't think the straight sections need concrete on every post, but it's so little extra work. Plus I think concrete does a better job of keeping the post dry and less exposed to microbes. At the top you slant the concrete away from the post to reduce water accumulation.
So, after 5 or 10 years, hurricane Sandy brought down some massive trees on my fence so I had a bunch of posts to dig out and replace. The concrete was less of a problem than I expected. The buried parts posts were like new.
Don't know about the new pressure treated lumber but I have old pressure treated lumber in the ground with and without concrete that have held up for over 40 years.
We used pressure treated 4x4x8 to hold control panels for irrigation systems. A lot of those things are doing well after 30 years. We started setting them in concrete maybe 20 years ago. It was easier and faster. We tamped the concrete mix a little just as if we were tamping soil. I used a ground rod for a tamper. NO water. Do you need square posts? If not check out creosote posts. I think one can still get them. Or there are hedge posts. Picture here:
My deck posts were cedar installed in concrete (dry mix tamped into hole around the post then watered in place) and when they required replacement I was able to jack the 4X4 out of the concrete and simply drop new posts into the holes in the concrete in 4 of 6 holes
if the posts were pressure-treated or not. A guy who we might hire to replace them suggested anchoring them in concrete.
Isn't the problem that it rotted, not that it wasn't anchored?
they could be expected to last at least five years without concrete. Is this true?
Heck yes. My ROUND posts have lasted 41 years. I presume they were treated.
concrete plug.
I agree with that.
Unless there's another resson to use concrete, I dont' see it. I think the guy you might hire has a rule in his head that concrete anchoring is good, and it is some of the time, especially I guess if the fence would otherwise be unstable. But your problem is rotting.
How old is the fence? 3 posts were rotten after only 5 years?? N years?
My rails and pickets are not treated, only my posts. Some pickets were being eaten by termites, and in a couple places the termites followed the picket to the rail. Went to an exterminator's home. Her husband and children were all out working but the wife took 10 minutes to talk to me. She said it's a mistake to use poison in that situation, just cut off the pickets so they didn't reach the grass and the termites won't be able to get into them. That's what I did 20 years ago and it worked. That's not your problem either but I like talking about an honest person.
My fence has about 60 posts, but bear in mind that they are round, not square.
The fence is 41 years old, about 42 inches high, picket fence, with an empty space one picket wide alternating with pickets. Wood, unpainted.
I presume the posts were treated since all but one are 41 years old.
About 5 years one post broke. Maybe someone fell against it while walking by. Only 2 people walk by regularly but repairmen etc. do occasionally.
No post is set in concrete. The ground has substantial clay so they stay in place, but I think that is rather unrelated to life-span.
Dug it out to some extent, watered the hole a lot, then put a big screw into the stub of the post, attached a chain, wrapped around a horizontal board or pipe and used a pair of jacks to pull out the stub.
Put the new post in, then used a sledge to get it in farther. Then cut it off to the right height. Looks like all the others except the other are rotting a little bit in the top, where water sits sometimes. Especially the ones that are in the shade almost all day.
I didn't ask in my other comment if these are corner or end posts. That might make a difference on how to set them. The post's lifetime might vary a bit too. The posts could outlast you at any rate unless you still have pimples. There are still fences around with barbed wire pulled tight without any concrete for the end or corner posts.
Anchor Fence Post in Concrete (or not) snipped-for-privacy@yahoo.com Nov 6, 2020, 1:32:17 PM (yesterday) A recent storm (Zeta) broke three 4x4 fence supports because they were rotten at ground level and had no strength. I have no idea if the posts were pressure-treated or not. A guy who we might hire to replace them suggested anchoring them in concrete.
I'm looking for information and advice on this because it seems feasible that if treated posts were used, they could be expected to last at least five years without concrete. Is this true? In addition, when they DO need to be replaced again, it'll be way easier without having to dig up the old concrete plug. If someone here has experience relevant to this situation, I'm very interested in your thoughts about this.
Thanks!
Nov 6, 2020, 1:42:48 PM (yesterday) You should read what Bob Vila of "This Old House" says about the subject
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Dan Espen Nov 6, 2020, 2:09:52 PM (yesterday) I put in a couple hundred feet of 6ft fence using 4x4s. I also have experience repairing storm damage to that fence.
The 4x4 posts should be specifically rated to be put in the ground. Regular pressure treated is no good.
I set all of mine in concrete. I don't think the straight sections need concrete on every post, but it's so little extra work. Plus I think concrete does a better job of keeping the post dry and less exposed to microbes. At the top you slant the concrete away from the post to reduce water accumulation.
So, after 5 or 10 years, hurricane Sandy brought down some massive trees on my fence so I had a bunch of posts to dig out and replace. The concrete was less of a problem than I expected. The buried parts of the posts were like new.
Frank Nov 6, 2020, 2:36:18 PM (yesterday) Don't know about the new pressure treated lumber but I have old pressure treated lumber in the ground with and without concrete that have held up for over 40 years.
Dean Hoffman Nov 6, 2020, 2:59:00 PM (yesterday) We used pressure treated 4x4x8 to hold control panels for irrigation systems. A lot of those things are doing well after 30 years. We started setting them in concrete maybe 20 years ago. It was easier and faster. We tamped the concrete mix a little just as if we were tamping soil. I used a ground rod for a tamper. NO water.
Do you need square posts? If not check out creosote posts. I think one can still get them. Or there are hedge posts. Picture here:
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They're tough.
Clare Snyder Nov 6, 2020, 10:02:13 PM (9 hours ago) My deck posts were cedar installed in concrete (dry mix tamped into hole around the post then watered in place) and when they required replacement I was able to jack the 4X4 out of the concrete and simply drop new posts into the holes in the concrete in 4 of 6 holes
micky
5:42 AM (1 hour ago) >A recent storm (Zeta) broke three 4x4 fence supports because they were rotten at ground level and had no strength. I have no idea
if the posts were pressure-treated or not. A guy who we might hire to replace them suggested anchoring them in concrete.
Isn't the problem that it rotted, not that it wasn't anchored?
they could be expected to last at least five years without concrete. Is this true?
Heck yes. My ROUND posts have lasted 41 years. I presume they were treated.
concrete plug.
I agree with that.
Unless there's another resson to use concrete, I dont' see it. I think the guy you might hire has a rule in his head that concrete anchoring is good, and it is some of the time, especially I guess if the fence would otherwise be unstable. But your problem is rotting.
How old is the fence? 3 posts were rotten after only 5 years?? N years?
My rails and pickets are not treated, only my posts. Some pickets were being eaten by termites, and in a couple places the termites followed the picket to the rail. Went to an exterminator's home. Her husband and children were all out working but the wife took 10 minutes to talk to me. She said it's a mistake to use poison in that situation, just cut off the pickets so they didn't reach the grass and the termites won't be able to get into them. That's what I did 20 years ago and it worked. That's not your problem either but I like talking about an honest person.
My fence has about 60 posts, but bear in mind that they are round, not square.
The fence is 41 years old, about 42 inches high, picket fence, with an empty space one picket wide alternating with pickets. Wood, unpainted.
I presume the posts were treated since all but one are 41 years old.
About 5 years one post broke. Maybe someone fell against it while walking by. Only 2 people walk by regularly but repairmen etc. do occasionally.
No post is set in concrete. The ground has substantial clay so they stay in place, but I think that is rather unrelated to life-span.
Dug it out to some extent, watered the hole a lot, then put a big screw into the stub of the post, attached a chain, wrapped around a horizontal board or pipe and used a pair of jacks to pull out the stub.
Put the new post in, then used a sledge to get it in farther. Then cut it off to the right height. Looks like all the others except the other are rotting a little bit in the top, where water sits sometimes. Especially the ones that are in the shade almost all day.
Dean Hoffman
6:11 AM (1 hour ago) On 11/6/20 1:32 PM, snipped-for-privacy@yahoo.com wrote: I didn't ask in my other comment if these are corner or end posts. That might make a difference on how to set them. The post's lifetime might vary a bit too. The posts could outlast you at any rate unless you still have pimples. There are still fences around with barbed wire pulled tight without any concrete for the end or corner posts.
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This is the OP. Thanks to all of you for your interesting and informative comments. Regarding the first response: I enjoyed reading the Bob Villa article but since the advice here in this thread is split on whether to use concrete or not, I'm leaning toward not. But I really like the part about packing gravel in the bottom of the hole to let water drain.
Dan Espen: Thanks for pointing out that there are different types of treated lumber. This 4x4x10 from Lowes says "Suitable for burial or contact with the ground and fresh water immersion applications" so that sounds exactly like the right item.
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Dean Hoffman: Yes, the rest of the fence has square posts and since I'm only going to have three replaced, I need to stay with square. And these three posts are in the middle of a straight run, not corners or ends.
Mickey: You're right - the problem was that the old posts rotted, not that they weren't anchored effectively. I don't know how old the fence is - I only bought the house four years ago. Last year, I had to replace two 8' sections because the posts and rails were both rotting so the slats were very loose. The dog took advantage of this to escape from the back yard and run free for an hour freaking out my wife. The rest of the fence seems reasonably solid right now but I figure that I'll have to replace the whole thing (about 140') some time in the next 3-5 years.
Not sure why you included that comment about round posts. Do they last longer than square posts? I can't imagine why that might be true.
This is the OP. Thanks to all of you for your interesting and informative comments. Regarding the first response: I enjoyed reading the Bob Villa article but since the advice here in this thread is split on whether to use concrete or not, I'm leaning toward not. But I really like the part about packing gravel in the bottom of the hole to let water drain.
Dan Espen: Thanks for pointing out that there are different types of treated lumber. This 4x4x10 from Lowes says "Suitable for burial or contact with the ground and fresh water immersion applications" so that sounds exactly like the right item.
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Dean Hoffman: Yes, the rest of the fence has square posts and since I'm only going to have three replaced, I need to stay with square. And these three posts are in the middle of a straight run, not corners or ends.
Mickey: You're right - the problem was that the old posts rotted, not that they weren't anchored effectively. I don't know how old the fence is - I only bought the house four years ago. Last year, I had to replace two 8' sections because the posts and rails were both rotting so the slats were very loose. The dog took advantage of this to escape from the back yard and run free for an hour freaking out my wife. The rest of the fence seems reasonably solid right now but I figure that I'll have to replace the whole thing (about 140') some time in the next 3-5 years.
Not sure why you included that comment about round posts. Do they last longer than square posts? I can't imagine why that might be true.
Let me add that my one post only rotted at ground level and a little below it. More than an inch or so below ground or above ground the post was still good. I haven't noticed any rot at all in the other posts, at ground level or anywhere (except in the middle of the top end. You can buy caps for square posts, but not for round ones. So I bought** some plastic and was going to make some but haven't done that yet.
**Actually it came from the rack with free plastic, leftovers, but it's just the color, thickeness, etc, that I wanted.
Absolutely.
I wasn't saying that. I think I was just being thorough. Maybe I mentioned it because I bought my post at a farm store, and they only had round posts. Not a lumber yard.
I am not saying this is so, but maybe if they're made for a different market they use, or could conceivably use, a different treatment.
Also not relevant, but a story anyhow: I had a summer job once in the middle of Chicago where I had to put some kind of wood in a long vat to soak up creosote or something. Maybe it was not available pre-treated in those days, 1968, or it was cheaper for the contractor to do it himself. I don't remember for sure what the wood was used for, maybe a fence. I wasn't there long.
Maybe because you can still find round 2.5 CCA posts. (what they use for telephone poles and salt water pilings) The problem is they usually start at 6" in diameter but in the ground they will outlive all of us.
That is always where posts fail. In the ground there is no oxygen to promote the rot. It is right at the interface where it finds the perfect storm of moisture and oxygen.
County required my new deck posts be down 3 ft (below the frost line but that is BS) and sit on concrete but the contractor filled around posts with gravel.
There IS a reason. Square posts are round posts that have every ring cut 4 times. This opens the "grain" of the wood allowing it to suck in water like an open cell sponge. A round post draws water in basically from the ends which can be readily treated.
I just remembered some round fence posts set in concrete. The concrete was cylinder shaped and extended a few inches above ground and was sloped down away from the post to drain the water away. I couldn't find any pictures. There are so called post protectors on line. I have no idea if they offer any benefit. They would possibly help if they fit tight like heat shrink over underground wire. The heat shrink fits tight enough to keep the water away from the splice.
The Lowes website has two types of Severe Weather 4-in x 4-in x 8-ft #2 Pressure Treated Lumber: Item #639138, Model #11687 for $11.22
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Item #552328, Model #Y2L40408-GC for $18.57
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Both posts are listed as:
#2 grade southern yellow pine
Severe Weather Ground Contact pressure treated exterior wood protected with Copper Azole (CA-C) provides lasting support and protection for all-purpose applications
Suitable for burial or contact with the ground and fresh water immersion applications
However, the specifications section for these indicates that the first one is not suitable "For Use with Fencing" while the second one is. Can anyone here tell me why, or at least provide a reasonable guess?
And while you're guessing, how long might each of these posts be expected to last before rotting at ground level with 2' buried, either using concrete or not? New Orleans gets an average annual rainfall of 64 inches with an average of 56 rainy days a year which makes us the third rainiest city of 200 U.S. locations surveyed. (Pensacola Fla. and Mobile, Ala. get more. Source: WeatherBill.com.)
If it's reasonably likely that I will get 3 years life out of the cheaper post without using concrete, that would seem to be the optimal solution for a temporary repair job. I suspect the whole fence will need to be replaced in a few years but I want to defer that if feasible.
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