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Waterproofing a Semi-Underground Wall That's Part of Extension

Postby Kenny000666 » Wed Apr 04, 2018 11:54 pm


My property is on a slope. The extension we are building projects from a flat ground level to a raised ground level, where the new back wall effectively becomes a retaining wall retaining 600mm of ground.

I was unable to locate and standards that deal with this type of wall (nhbc, building reg approved docs etc.) I would like to understand what the best way to waterproof this is.

I anticipate the existing DPC level will continue through the new extension. However, to prevent any breaks to the DPC, it will need to remain on the same level when it reaches the retaining wall.

Assuming that tanking will be applied externally from foundations up to ground level, we should have all angles covered, (rising damp, penetrating damp), but I believe we are still missing the risk of splashing water on the raised ground level hence the general need for the DPC being 150mm above GL.

Would we need to do a vertical DPC around the blockwork and up to the supposed 150mm level? Or would we do 2 DPCs? Or maybe tank it 150mm above the raised ground level?
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