Instructables

How to fix and then extract a fence post with ease

Picture of How to fix and then extract a fence post with ease
Here's a video about this method.
http://www.youtube.com/watch?v=9A8i6mouohw
 
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Step 1: Traditional method

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I stopped using it a while ago, I care about my customers and myself.

Step 2: Reconcreting?!?

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when you dig up the lump of concrete you generally end up with a much bigger hole and you might have  to use a lot more concrete as shown on the picture to fix the new fence post. See for instance the havoc created at minute 0:50 on youtube video http://www.youtube.com/watch?v=9A8i6mouohw 
More work, more material, more costs. All this can be avoided.

Step 3: Keep a gap!

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this is a way to re-use the concrete foundation

Step 4: Apply the spacers

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The spacers will keep a uniform gap between the post and the bag

Step 5: Insert the post socket bag

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the socket bag is specifically designed for the purpose of fitting a 100x100mm (4"x4") section fence post. The bag is fairly robust and 900mm (3ft) long to cover any eventuality and ground conditions but can be easily cut to a shorter lenghth

Step 6: Fill the gap with dry sand

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fill the gap with dry sand and pat while doing it to create a grip between the socket and the post

Step 7: Insert some foam on the top

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the material used is off cuts of insulation pipes, this is to separate the silicon from the dry sand

Step 8: Silicon it

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seal the top with silicon to keep the water out.

Step 9: Concrete it

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insert the post into the ground and concrete it in.

Step 10: Suck it out

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to extract the post, cut the  silicon seal and suck the sand out with a vacuum cleaner

Step 11: Replace

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now you have a hollow foundation and can replace the post re-using the dry sand.

Step 12: Concrete out?

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should you need to remove the concrete foundation completely due to ground movement or change of plans, it is still far easier  to do so as the hollow fondation can be broken into pieces with the aid of a metal spike like I did in this trial. And the hole on the ground keeps more or less the original shape without getting bigger as it happens when removing a solid block of concrete.
RoBear6136 months ago

By planting the post in concrete or using a bag, you wind up holding water next to the post. This can resulting in premature rotting. Why not just put a bed of drainage material in the bottom and tamp something like rock dust in around he post? It drains after rains and you don't have any water held next to the post.

robz40 (author)  RoBear6136 months ago

I tried it, drainage is not enough. The problem is the constant presence of moisture and air which is essential for microorganism to prosper and damage the wood. In britain a moisted ground is pretty much the norm.

f1dd13r1 year ago
Nice .
Where to get large amounts of silicone? and where to get the bags from?
robz40 (author)  f1dd13r1 year ago
bags from http://myworld.ebay.co.uk/easyfencing , you don't need a large amount of silicone about 1/2 tube per post and you can get good prices from ebay or use flexacryl which is much stickier and better but more expensive.
really interesting
Mr.Miz4 years ago
Couldn't you just put the plastic bag around the post and then stick it in concrete then the concrete wouldn't bond to the post? I've never tried it, but wouldn't it make a concrete sleeve?
robz40 (author)  Mr.Miz4 years ago
Not advisable, the post is never perfect and it would be just as hard to extract it. You need a gap, trust me on that. Or you can make an experiment ;-)
rimar20004 years ago
Maybe this work worth if you think to extract the post soon. But for me, when I put a post I think it will last many many years.
robz40 (author)  rimar20004 years ago
"But for me, when I put a post I think it will last many many years." fair comment, posts should (underline should ) last many years but it all depends on ground conditions, execution and natural events (eg storms). On the video I posted, the pictures at minutes 0:36 and 0|:37 do actually come from one of my customers and the fence had been previously installed only 3 years earlier. All because of this http://www.metoffice.gov.uk/corporate/pressoffice/2009/ht20091117.html
Well, do not feel bad. What happens is that here in Argentina, or at least in the area where I live, the posts are almost all of break-ax (quebracho), a very hard and heavy wood that will not rot, and therefore they are plowed under without cement aggregate. Moreover, here the storms aren't frequent, and hurricanes are a very rare thing.
robz40 (author)  rimar20004 years ago
All comments are welcome rimar2000 and I still feel good because my customers love the new system :-) I live and work in Britain and here the weather is pretty fresh, damp and windy, that's why fence posts may not last many years. In Britain fence posts are generally made of pine wood treated with CCB compounds (Chromium, Copper and Boron). CCA compounds (A stands for Arsenic) were used in the past and were more effective but it has now been banned thus making the posts last even less than they used to.
Here some people process the soft wood posts (spruce, eucalyptus, palm, etc) with hot tar (asphalt), it seems it enhances the protection, but I don't know details. Your system is good, surely.
paperrhino4 years ago
This is a very clever solution though it would not do much good in an area that has a highly mobile clay like soil (e.g. North Texas). When we need to replace a fence post in this area, it is often because the ground moved, causing the post and concrete foundation to tilt, eliminating the possibility of reusing the foundation in this way.
robz40 (author)  paperrhino4 years ago
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robz40 (author)  robz404 years ago
Hi paperrhino, thank you for you comment. Even on clay soil it is a win win situation. Let me explain. This method leaves a gap of about 25mm all around the post so even if the foundation moves a little there is still margin to manoeuvre by leaving a non uniform gap around and keep the new post straight when it gets fixed in the same way. Should you need to replace the foundation completely it is much easier to break up in pieces a hollow "cement pipe" than a solid lump of concrete. Pictures added to illustrate the result
dchall84 years ago
On the surface this looks like a great idea, but it is a lot of extra work for the original installer.  He has to dig a bigger hole to fit both the sand and concrete.  He has to use considerably more concrete (twice as much??).  There would be more materials required with the addition of the sand, the extra long Subway sandwich bags, and the little pieces of foam and tie wraps.  And there is additional labor involved in bagging the post before dropping it in the hole. 

The video does a good job of showing the various ways of extracting an old post, and implies that extracting this post would be easier.  I don't understand why that would be. Yes you don't have to hoist the concrete, but you still have to get a grip on the post and pull it out somehow.  Seems like the traditional extraction methods are still needed. 

As for reinstalling a new post if you ever have to: that was really glossed over in the video.  If you have removed the post and vacuumed the sand, how do you put a new bagged post in without ripping the bag on the concrete?  And if the new bagged post goes in that easily, wouldn't it be loose?  Or do you set a new, bare post and then just fill with sand around it? 

Are posts supposed to last longer using your method?  It would seem like they would if they are kept dry. 
robz40 (author)  dchall84 years ago
Hi dchall8 Tx for your comments, they are a good contribution.
the method requires more work but not considerable more work. the diamater of the socket filled with sand is about 190mm=7&1/2 inches so if you dig a standard hole 1ft wide that leaves a gap between the post and the ground of about (300-190)/2= 55mm=2inches. Personnaly I do not use ballast and cement but sand and cement for the job either dry or wet according to the job. The added material cost per post is about £5 (maybe 8$) but replacing a concreted broken post is considerably more, typically I charge at least 100$ because of the labour and extra materials involved.

the post socket is 900=3ft long to cover any conditions but can be cut to size to fit a 500 or 600mm (2ft) deep hole s I normally do.

Traditional extraction methods are not needed.When the sand is extracted there is nothing gripping the post and it comes out with ease.

The bag is quite robust and can be reused as it stands. I concede that accidents might happen and a new bag is needed. That is not a problem as you insert the bag first into the hole , a bit of sand then the post and fill it with sand which will expand the bag

As you said keeping the moisture out of the base of the post makes it last longer. Should any water penetrate anyway you would not be in a worst condition the the traditional post and concrete method and as a precaution you can always add boron salts at the base of the socket. The water would dissolve the salts with would penetrate the wood thus preserving the wood.

I have been using this method for 3 years and no customers has called me back to replace any of the posts.