rebuilding a collapsed stone wall

7 Sep 2010
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United Kingdom

Just before Christmas a retaining wall collapsed at my house as a result of tree root movement. Unfortunately the insurance says its not covered so I have to rebuild it myself.

The wall is about 200 years old. The tree has been chopped down.

The wall that has collapsed is about 25 metres long but only about 10 metres has collapsed. it is 1.8metres tall. It is built of random sized sandstone blocks. The front skin is nice finished stone but behind the wall is big hunks of sandstone rubble.

I have taken out all of the back rubble and am left with a vertical face of soil.

My plan is to build two skins of walling. a backing skin of dense concrete blocks and a front skin of the sandstone. then backfill any gap to the soil with aggregate

My issue is that because the sandstone blocks are quite randomly sized how do I tie them to the dense blocks behind because the top of the sandstone block is never likely to be at the top of a dense block. Are there any special ties available that can accomodate this?

then i though should i not just be making this a solid wall with the dense blocks being mortared directly to the sandstone blocks. Is that a better solution?

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im not sure what you mean by sandstone blocks a pic would help , but i woould of thought you should be able to cousre it with the blockwork behind , failing that you could cut strips of expanding metal and use that , i would also fill the cavity with dryish concrete :D

these are the sandstone blocks I'm on about.

I've had another thought of how to do it.

I will build the front skin of sandstone and insert butterfly ties as I go along sticking out the back. then once complete I will pour readymixed concrete down the back to lock onto the ties.

The only problem is the gap between the sanstone blocks and the soil will be about 50cm so that a heck of a lot of concrete (9 cubic megtres to be precise) so I don't want to risk pushing the wall over with the weight when its poured (it will be pumped so more liquidy that a normal mix)

so I would need some kind of shuttering solution. I'm thinking fix some plywood in between so the gap for concrete is only about 10cm. but how could I fix the plywood in place enough to hold the weight of the backfill I'd use in the rest of the gap. I'd only have 10cm to play with. maybe put some rocks at the bottom of it to stop it kicking out, then a batten across it's length so I could put some support resting on the batten and pushing against the front sandstone skin.

is this an option worth considering. I'm trying to reduce the time its going to take without breaking the bank.....

wow those blocks are huge they look man enough on there own !!

having said that putting 9 m2 of concrete behind it is a no no it will simply push the wall over and is not needed any way , your plan of 100 mm is better ,

is thier a concrete footing under your new bit ?
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The stones that fell over were set directly upon the road tarmac but I haven't dug down enough yet to see how far back the road extends to determine if the concrete pour will be also onto the road.

That's made think now though. If the road ends and the concrete just goes onto the soil does it need its own footing. when say soil I mean the soil is clay so its very firm and in effect the concrete pour is like one massive footing on top of that clay.

So i'd only be digging out more clay to put more concrete in.....

Or am I wrong and actually I need a footing?
don,t build on the clay mate its about the worst soil to build on !! better to have a conc footing and put some reinforceing bar up out the concrete 50mm behind your stonework so its in the middle of your 100mm thick concrete backwall :)

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