# Forum Home Renovation Fences & Screens  Treated pine versus treated pine with steel posts versus repair

## davewastech

Hi folks, 
My 1.8m treated pine fence is in need of replacement (or repair). Some of the 125 x 50 treated pine posts have rotted thru below ground. Otherwise the fence looks reasonable. People in the neighbourhood think it's about 8 years old. 
The old posts were set in concrete, but the tops of the concrete are about 250mm below the surface. Soil is clay and it's rather damp (near Chatswood, Sydney). 
So I feel that 8 years is too short a life for a fence. Is this typical? 
What do readers think about replacing the fence with a treated pine fence with steel posts? 
Also is repairing the rotted posts an option?  For example I found this product online from USA Stur-D Fence Post Brackets » The solution to leaning or broken fence posts. Stur-D Fence Post Brackets are sturdy, made in the U.S.A. of recycled steel and powder coated for durability. Stur-D Fence Post Brackets . Is anything similar available in Australia? 
Thanks for all replies.
Dave

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## shauck

I like to use cypress posts 125x75. Not concreted in but cement stabilised dirt. So a few shovel fulls thrown into the dirt and mixed and then backfilled and tamped. Get the posts out and replace, I reckon.

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## phild01

I have to wonder if the original posts were H4 :Confused:

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## chalkyt

Two thoughts come to mind. Firstly a local steel fabricator could probably make something like the Stur-D and get it galvanised. It looks like a reasonable solution. Secondly, are there any standard post stirrups that could do the job. I had a similar situation at Turramurra and found that TP posts didn't last in the damp ground. Similarly, the only thing that hardwood fences were good for was a regular supply of firewood. In the end we went with colourbond fence with steel posts.

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## davewastech

> I have to wonder if the original posts were H4

  Yeah, I wondered about that too. I've since found an old thread* with a link to a very informative article about failure of H4 treated sawn pine posts in the soil. The problem is that the preservative only penetrates the soft sapwood (outer part of tree trunk) and not the harder heartwood (inner part of trunk). See article at Timber in the landscape  . So if a post had 80% sapwood it would last well, but if it only had 30% sapwood then it will rot thru fast. 
I read another article that states that the penetration of the preservative in sawn radiata pine is typically only 30% to 40% despite AS 1604 stating it should be at least 80%. See Timber Building in Australia  Yes I know this article is old, but the points may still be valid. 
I had a look at a rack full of H4 pine sleepers in a hardware store, and sure enough if you look at the sawn ends the green colour is all in the sapwood. There was quite a lot of sleepers that contained the center part of the tree, and that part didn't look green. 
The more I read around the topic the better galvanized steel posts are looking! 
Thanks for help, 
Cheers,
Dave 
* See Strangerep's article -   http://www.renovateforum.com/f196/ti...76/#post876556

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## davewastech

> Two thoughts come to mind. Firstly a local steel fabricator could probably make something like the Stur-D and get it galvanised. It looks like a reasonable solution. Secondly, are there any standard post stirrups that could do the job. I had a similar situation at Turramurra and found that TP posts didn't last in the damp ground. Similarly, the only thing that hardwood fences were good for was a regular supply of firewood. In the end we went with colourbond fence with steel posts.

  I had a look around online and in Bunnings but didn't find a post stirrup suitable for this job. The concrete that the posts are set in is about 250mm across. I could mimick the Stur-D by bolting a length of 90 x 90 treated pine side-by-side to the above-ground part of the existing pole and then bolt onto the pair a length of galvanised pole going 600mm below ground. Fill up the hole with concrete. The purpose of the 90 x 90 is, as with the Stur-D, to avoid the old concrete footing. Wouldn't look pretty, but it will be behind some bushes. 
Thanks for reply,
Cheers,
Dave

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## shauck

Seriously, just use cypress posts. They're naturally rated for in-ground use. I also wouldn't use treated pine for sleepers but red gum all day.

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## davewastech

> I like to use cypress posts 125x75. Not concreted in but cement stabilised dirt. So a few shovel fulls thrown into the dirt and mixed and then backfilled and tamped. Get the posts out and replace, I reckon.

  Hi Shauck, 
A couple of questions (I've never built a fence before; or even repaired one):
1.  getting the old concrete lumps out of the soil looks like serious work. So replacing just the posts (and saving the rest of the fence) might just not be worth the effort because I'd have to get the lump out to make room for the new post(?) 
2.  Are there any issues in having cypress posts supporting a treated pine fence? I've seen plenty of 50 x 50 steel posts used in treated pine fences, but can't say I've noticed cypress. Maybe I just assumed they were all pine. 
3. I've seen guys just mixing up cement with dirt (clay in my case) and backfilling. Apart from being easier and cheaper than mixing concrete, is there any advantage? I'd worry that it might not be as strong 
Thanks for the info,
Regards,
Dave

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## shauck

> Hi Shauck, 
> A couple of questions (I've never built a fence before; or even repaired one):
> 1.  getting the old concrete lumps out of the soil looks like serious work. So replacing just the posts (and saving the rest of the fence) might just not be worth the effort because I'd have to get the lump out to make room for the new post(?) 
> 2.  Are there any issues in having cypress posts supporting a treated pine fence? I've seen plenty of 50 x 50 steel posts used in treated pine fences, but can't say I've noticed cypress. Maybe I just assumed they were all pine. 
> 3. I've seen guys just mixing up cement with dirt (clay in my case) and backfilling. Apart from being easier and cheaper than mixing concrete, is there any advantage? I'd worry that it might not be as strong 
> Thanks for the info,
> Regards,
> Dave

  Probably the best method I've seen for removing a post (although it was not with concrete, but can't see how it would be that different), crow bar to loosen soil around the post, or in your case, around the concrete. Pour water in around the post, loosen as much as is reasonable without killing yourself. Attach a block of timber to the post at desired height. If replacing rail then you'd just cut it off next to post and use what remains as the block but in your case, I'd imagine you're saving the rails so un-fix them from post and remove palings in the way. Get your hands on a high lift jack. Sit it on a solid piece of timber, such as a piece of redgum sleeper, wedge it under the block and lever the post out.  
There are no issues using cypress posts with treated pine as far as I know. Naturally durable for inground use, naturally termite resistant. Cheaper than treated pine or redgum, at least in my experience. Probably what you have seen is treated pine but personally I've gotten used to using cypress for fence posts, decks, subfloor stumps, etc.  
As far as I know, concreting timber in the ground is more of an issue that leads to rot. Stabilised dirt is a better option for timber fence posts. Yes it's very strong and sets hard. Use same method as dirt backfill, tamping as you go. Sit post on a sole plate.

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## davewastech

> Probably the best method I've seen for removing a post (although it was not with concrete, but can't see how it would be that different), crow bar to loosen soil around the post, or in your case, around the concrete. Pour water in around the post, loosen as much as is reasonable without killing yourself. Attach a block of timber to the post at desired height. If replacing rail then you'd just cut it off next to post and use what remains as the block but in your case, I'd imagine you're saving the rails so un-fix them from post and remove palings in the way. Get your hands on a high lift jack. Sit it on a solid piece of timber, such as a piece of redgum sleeper, wedge it under the block and lever the post out.  
> There are no issues using cypress posts with treated pine as far as I know. Naturally durable for inground use, naturally termite resistant. Cheaper than treated pine or redgum, at least in my experience. Probably what you have seen is treated pine but personally I've gotten used to using cypress for fence posts, decks, subfloor stumps, etc.  
> As far as I know, concreting timber in the ground is more of an issue that leads to rot. Stabilised dirt is a better option for timber fence posts. Yes it's very strong and sets hard. Use same method as dirt backfill, tamping as you go. Sit post on a sole plate.

  Thanks Shauck, 
Yeah, I read an old thread that stated that concreting the post makes it rot faster. Reason given was that it was like building a little dam around the bottom of the post to trap the water in. The water presumably mostly soaks down the post from above. Perhaps stabilised dirt drains better (?) At least I can say some of my posts have rotted through, and they were set in concrete - although the top of the concrete was about 250mm below the surface for some reason not obvious to me.  
Seems to be a range of opinions on concreting though. 
Cheers,
Dave

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## shauck

> Thanks Shauck, 
> Yeah, I read an old thread that stated that concreting the post makes it rot faster. Reason given was that it was like building a little dam around the bottom of the post to trap the water in. The water presumably mostly soaks down the post from above. Perhaps stabilised dirt drains better (?) At least I can say some of my posts have rotted through, and they were set in concrete - although the top of the concrete was about 250mm below the surface for some reason not obvious to me.  
> Seems to be a range of opinions on concreting though. 
> Cheers,
> Dave

  You'll always find different opinions, no matter the subject but I've heard plenty of support for dirt backfilling timber fence posts over concreting them. I've also heard that timber posts in concrete can rot at the top where the concrete starts. Was the concrete sloped away from the post, even though it was 250mm below the surface? Any concrete filled post/stump hole should be sloped away, to allow water to run away as much as possible.

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## davewastech

> You'll always find different opinions, no matter the subject but I've heard plenty of support for dirt backfilling timber fence posts over concreting them. I've also heard that timber posts in concrete can rot at the top where the concrete starts. Was the concrete sloped away from the post, even though it was 250mm below the surface? Any concrete filled post/stump hole should be sloped away, to allow water to run away as much as possible.

  Yes, the concrete was sloping away from it, although the concrete was rather rough on the top. Any idea why the top 250mm of the hole wasn't also filled with concrete? 
Also my posts were just 50 x 150mm. Once my 50mm had rotted down to about 20mm of soggy pine the post just wobbled around with almost zero strength left in it. I suppose if the posts were 75mm then they would last longer. 
Cheers,
Dave

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## shauck

I don't think it's unusual to finish the hole off with tamped dirt. I've done that before on subfloor stumps. Concrete most of the hole and tamped dirt to make it solid straight away, walk away, finished rather than it still moving about on you, waiting for concrete to set. 75mm would have to be better than 50mm.

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## phild01

Have always laid aggregate of some sort in post hole for post to sit directly, then laid concrete around post only and finished above ground sloped away.  I thought this was general practice.

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## davewastech

Well from reading around in this forum, and in some of the links, and various authorities, and from looking at my own fence I can only conclude that there are several variations of usual practice for setting a TP post:
1. As Phild1 describes - aggregate in the bottom, concreted to above ground.
2. Quite a few say that aggregate just produces a pond for the water to drain into and rot the post.
3. As Shauck and others describe - cement mixed up with soil and tamped.
4. Somewhere I read concrete at the bottom, tamped soil in the middle, and a concrete collar at the top.
5. Mine were concrete, but the top 250mm was just soil. (Failing after approx 8 years) 
Alarmingly the article   Timber in the landscape suggests that the penetration of preservative into sawn radiata pine is variable, but typically only 30% to 40%.  :Shock:   No wonder some posts quickly rot - maybe regardless of how they're set.

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## phild01

Soil conditions may come into play. Ponding might be an issue with higher than normal water tables.  Encasing the post in concrete would be worse as it provides permanent water capture for the post.  Mixing concrete with soil should be ok.  I am wondering if your post was cut short with an untreated cut and if this makes any difference.  What you describe as failure ...is the soil soggy or very wet?

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## davewastech

> Soil conditions may come into play. Ponding might be an issue with higher than normal water tables.  Encasing the post in concrete would be worse as it provides permanent water capture for the post.  Mixing concrete with soil should be ok.  I am wondering if your post was cut short with an untreated cut and if this makes any difference.  What you describe as failure ...is the soil soggy or very wet?

  Soil is clay, and it's at the down-slope end of my property. I dug a hole down about 500mm to check out the post and concrete, and it was quite damp but water didn't pond in it after our recent rain. I didn't dig to the full depth of the concrete so I don't know if post was cut short, but given that there was concrete down to 500mm and further, I guess not (but ?). There used to be 4 big pine trees along that fence, but I had them removed 7 months ago, so those trees would have sucked out some of the water. There was also black plastic sheet about 200mm below the ground and covering from the fence to at least 2 meters away, the full length of the fence - possibly that trapped the rain water above it and kept the exposed part of the posts wet (?). The plastic looked very old.

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