Replacing a fence that has come down. Tried to dig a hole for the fence post
only to find the area has concrete just below the surface of the top soil.
Tried 3 or 4 other places along the fence line and this was the same. What
are my options? Looking on HSS hire website they have 'Demolition hammers',
is this my only option? Are there any 'add on' bits which can be fitted to
regular electric hammer drills to try and break up the concrete?
Would appreciate any comments, thanks
Sounds perfect. Bolt steel fence post bases to the concrete and drop the
posts in.. rather better than digging a hole, putting in a post and
filling around it with concrete to stabilise it.
If you really want to remove the concrete, it depends on base+thickness+
reinforcement. If it is on a rock base, is many inches thick and
reinforced, forget it. If it is on soil, a couple of inches thick and
without reinforcement, hit it with a sledgehammer. Only in between these
two do hand tools have a place.
Forget electric hammer drills. If that can do it - a sledge hammer will,
much more quickly and easily.
An electro-pneumatic tool is good in places where you can't swing a
sledge hammer. eg stood on scaffolding/ladder.
The alternative is a *proper* SDS-type drill tool with a *drill* bit.
Run a line of holes around and in the bit of concrete that you want to
remove and then hit that with a big hammer (or a bolster/chisel/etc).
Concrete is very strong under compression - so always break it in the
direction it is free to move, so that it fails under tension. eg slabs
on a solid base - break *upwards*. slabs on soil - break either up or
down. slabs against a wall - break away from the wall..obvious, really..
The concrete is not level, appears to be 'chunks' of concrete along where
the fence used to be. On the other hand, if I cannot break the concrete,
may level off the area and do as you suggest above. Thanks.
It sounds like the fence posts were put in by the method Sue describes, ie
digging a hole, putting in a post and
filling around it with concrete to stabilise it. This is the most common
method, because it's quick and it's cheap. Unfortunately it's the most
inconvenient when the posts rot off at soil level, which is usually only 3
years or so. Of course when you re-do the fence, you'll probably be wanting
to put posts in at 6' spacing which will be exactly where the lumps are.
Dig 'em out. Then you have the options of using concrete posts, or wooden
posts in Metpost sockets, stuff like that.
The moral of the story is (although this won't get you out of your
predicament) never concrete posts in. They rot off at ground level and then
there is a problem of getting the concrete out.
Posts should be rammed home with brickbats and stones. This takes effort,
but it's a lot more satisfactory (provided the ramming is done properly.
Mostly it isn't, so the post gets loose quickly.) I have two gate posts that
have been there 20 years and they are not concreted in, are not loose, and
cope with a 12 ft wide gate.
Having been in that position, the only answer is remove the concrete. I used
a heavy hammer and a large cold chisel to make a few lines for it to crack
along. I then used a sledge hammer to break it up into manageable chunks. I
did not fancy doing the job again in a few years time so bought concrete
posts and concreted the posts in. They have lasted thirty years so far and
now the problem is not the wet weather that rots the wooden posts but the
high winds that seem to be a regular happening round here. My fence is still
OK but the neighbour's fence isn't.
Regards Robbie in Surrey
If you want a long term solution, and it seems like you intend to remove the
concrete anyway. Use concrete posts and plinths, these don't rot or need
painting. Fence panels then slide in place and can be replaced relatively
easily in years to come.
I recently dug up 22 conifers and erected a concrete post and plinth fence.
I used a petrol hole borer and post mix to fit the posts. Once the trees
were out it was a straight forward job.
I am borrowing a friends Demolition hammer today. Going to have a go at
breaking up the concrete, or at least try and level it and then follow some
previous advice from here and bolt a fence post base to the concrete. I do
not want to spend huge amounts of money for a couple of reasons:-
1) We are moving, so long term stability is not my primary concern
2) We don't own the fence......no ones does apparently (bit of a grey area,
the Land Registry do not know who owns it), but the fence is a divider
between two levels (about a 2 foot drop) and is dangerous.
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