Replacing Corner Fence Post (8ft) 4"x4"

4 Sep 2009
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United Kingdom
i had to replace corner post and having spent quite some time removing old post and concrete base and am now left with a 'L' shaped hole, about 12" by 12". also the earth around the top of hole is sandy and not clay like or hard. has anyone any ideas as to how to proceed! the hole is around 30" deep and was thinking of using postcrete. i have heard of shuttering but no experience but thought maybe of tamping down earth to reduce size of hole might be worth a try
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Trying to get away with using just part of the hole is not going to work. So, shuttering is out of the question, from the conditions you describe.

I would be tempted to see if you could go deeper still, digging a narrower hole in the middle of your now huge hole. Will need a longer post though.
Or, just bite the bullet and fill the big hole with concrete.

Postcrete is more expensive than buying ballast and cement, and it sounds like you'll need a lot!
Hi Wabbitpoo, apologies but the hole is approx 20"x17" which is much larger than the 12"x12" i want. as the images show i had just started thinking about shuttering before your reply. i do not really want to place post in the middle of the hole as this would affect one of the boundaries which cannot really be changed due to a very large tree nearby. also i'd rather not go any deeper. i agree with you though that i think a lot of concrete is going to be needed if the only solution is to fill this crater!

only solution that will provide a solid post is to fill the hole around teh post with concrete. its not that big a hole. anything else will simply allow the post and concrete to move over time.
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Hi Thermo. would that be 1 part cement 5 parts aggregate? in terms of the finish could i leave the concrete 2" or 3" below ground level and backfill with soil and slope concrete away from post. what would be best for stability? thanks for your reply :D
pretty much spot on. put the mix in dry into the hole and ram it well in, then when its all lined up and your happy add the water and let it soak through.
now that you have found it such a job to dig out the old post (did it rot?) you might be in the frame of mind to use a concrete post next time. At least it will not rot so you may not need to do the job again.

That's what led me to resolve to use only concrete posts.
Much better to leave the concrete a few inches higher than the surrounding ground, sloping away from the post. A handful of pea shingle 'pebbledashed' into the exposed concrete will soften the visual impact of exposed concrete.
That way no part of the post will be in contact with soil and will be able to air dry after it's been rained on.
opinion appears to be divided as to whether the concrete ends above,at or below ground level so probably not that significant (but agreed to slope away from post so no moisture remains)
above is certainly better if you have wooden posts, as it can help reduce water ingress. But it will get down the crack in time and the post will rot, near the junction between "in the ground" and "in the air" where there is an ideal mix of air and water to support rot.

If using concrete posts, which do not rot, you can have the concrete just below the surface so it doesn't show.

A handy tip for making post concrete look neater, is to finish the great mass of it below ground, then put a small frame round the post a few inches high and put the last mix into it, so the concrete showing above ground is a small neat piece. A square frame can be made with scraps of wood, for a round one you can cut the bottom off an old bucket or large plastic tub or flowerpot
Hi Thermo,
i am still thinking about your suggestion to resolve my problem.

the top of the hole from corner of the L shape to the other corner at ground level is about 3' (36"!!) and the position of the post is off centre (towards the corner of the 'L'). Would i need to widen the hole to make the post the centre? (more concrete) would you advise on making the hole square. Or is it a case of filling with concrete and hoping for the best

As things stand, just adding concrete would create 'V' shaped (top heavy) concrete base,

i could perhaps dig a bit deeper and create a pyramid shaped/bottom heavy concrete base and finish the concrete 6" or so below ground level...this would mean the base of the post completely surrounded by concrete..

can anyone advise if shuttering is not a very good idea generally for post holes, or just in my situation.
shuttering between the concrete and the sides of the hole is not a good idea. The concrete should be surrounded by firm, well-compacted soil that has not been dug up. Hence you have to dig out all the disturbed soil and replace it with concrete. If you use shuttering, and then backfill afterwards, the concrete will only be supported by loose soil.

digging out the bottom of the hole will be good so that the base is surrounded by concrete and can't move towards the softer ground

if the hole is very big you can, for economy, pack round the post with large pieces of clean brick or broken concrete, so long as the mix packs tightly around then all and they set into a single solid mass
can anyone help regarding
put the mix in dry into the hole and ram it well in
do i add water initially to the proportions to create a dry/firm mix and then add water at the end of the day. thanks
If using postcrete then water can be added later, you could water the hole first, to moisten it but let any excess drain away before adding the mix.
Hi Deluks, due to amount of concrete required i have decided not to use postcrete on this corner hole but to mix my on concrete can you advise re my question regarding when to add the water to the mix

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