Help with a retaining wall

31 Oct 2015
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United Kingdom
Im planning a 10m long retaining wall (430mm high) to contain sub base for a patio. The edge of the patio will sit on top of the wall. Questions:

Will a double skinned wall using std building blocks be sufficient?

What size footings will the wall need? Width x depth? (area is currently laid to lawn)
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What do you by building blocks, I'm assuming you mean concrete blocks?

Double skinned is fine , have you considered drainage?

Without drainage you risk the soil expanding and pushing the blocks over especially over an 11 metre wall

It's only a small wall and I would go with 450mm wide and 150mm deep footings

I assume you've gone with 430mm high because that's the height of two blocks? If that's the case don't forget to allow 30mm for mortar
For that height you can build it 1/2 brick thick.

The foundations need to be at least 300mm wide, and whilst the concrete could be 150mm, it needs to start at a depth where its on solid ground, which means removing at about 300mm of soft top soil and then 150mm of the harder soil you find down there.

As the patio will be solid and presumably you are draining the surface somewhere, there is no need for drainage behind the wall.

Be careful how you detail the paving finishing on the wall and the bricks or blocks, if you don't want water to just run down the wall leaving a dirty mouldy mess and a frost blown face.
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Thanks gents, yes sorry I meant standard concrete blocks (440x215x100). What density should I go for if I’m double skinning it?

I’m wanting to render the retaining wall and paint it white.

I’ll probably go with 400mm wide foundations, and down 500mm to be safe (400mm compacted type 1, 100mm concrete)

Open to suggestions on how to detail the paving to the wall

As you can tell, I’m new to this but determined to master it

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