Lowering ground level with trench - how wide?

Postby peelypost » Tue Sep 22, 2009 3:15 pm


We need to lower external ground levels to below DPC and have been advised that we need a good 800mm width excavation. Does it really need to be this wide? I can't see how 800mm will be any more effective than 400mm with a grate on top.

What do you think?


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Simply Build It

Postby Perry525 » Wed Sep 23, 2009 5:38 pm

Its simple really, the idea behind lowering the ground outside, is that heavy rain bounces, depending on your location and how exposed you are, the rain will bounce and make the wall wet above the dpc.
The recommended level is six inches below the dpc, the width whatever you like, if your guess is wrong you can always deepen or widen the hole. (or both) I find that having pea shingle in the hole stops the rain from bouncing.
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Postby peelypost » Thu Sep 24, 2009 9:40 am

That explains it - thanks. I was thinking of hydrostatic pressures and just needing to break the ground contact - hadn't thought of the rain splash.

Pretty obvious really!

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