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Footing depth for concrete block retaining wall

Postby Justaddwater » Thu Jul 08, 2021 9:54 pm

I'm looking to build a retaining wall, probably in standard concrete blocks laid flat. It will be about 7m long and minimum of 1.3m high and will be filled behind with hardcore.

The ground I think is chalk, but my questions are:-

1. Will a 9" wall be ok without piers?

2. Am I better off making the wall wider by making it a cavity, or using hollow 'H' blocks?

3. What Depth and width should the footing be?
Justaddwater
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Postby stoneyboy » Fri Jul 09, 2021 9:06 pm

Hi justaddwater
Laying solid concrete blocks flat will be fine but use a strong mortar mix 4 or 5 to 1. Probably worth adding a pier at either end.
You will need 18” wide foundations but the depth will depend on ground conditions - you will have to dig deep enough to reach a very firm base ie a spade will not go in very far.
Regards S
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Postby Justaddwater » Fri Jul 09, 2021 11:33 pm

Thanks Stoneyboy.

Nice straightforward answer. I am just a bit concerned about the amount of weight on the footing with just the height of blocks on top
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Postby stoneyboy » Sun Jul 11, 2021 8:38 pm

Hi justaddwater
In terms of the depth of the foundation itself you will need to make them at least 200mm, you could add rebar if you do not get down to a solid base.
Regards S
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