DPC/DPM in wall below external ground level.


22 Jan 2010
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United Kingdom
I'm rebuilding a 9 inch wall (on the existing foundations) and I just wanted some advice on whether I've got the right set up in regards to the DPC and vertical DPM.

The external floor level (concrete) is about 45cm higher than the internal floor level. Currently there is no dpc/dpm in the wall, so lots of damp on the inside wall. The internal floor is tiled, and I wont be lifting the tiles.

Q1. Is the detail in the attached drawing correct? am I missing anything in this set up?

Q2. What is the best vertical DPM to use in this instance? At the moment the options are:

1) Insert a 1200g plastic DPM sheet between the inner block and outer brick .
2) Build the external leaf first and then paint it with a liquid DPM (eg Black Jack DPM) and then build the internal leaf.
3) Build the external leaf first then stick Bituthene 3000 on the inside part of the engineering brickwork, and then build the inner block wall.

The internal room is a shop - I would prefer to have the DPM sandwiched so the tenant doesn't puncture the DPM if they ever drill into the wall. Access to waterproof the wall externally is restricted.




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Thing that springs to mind... will you not be using ties to bridge the block and brick skins together? If so these will have to puncture the DPM, as your sketch. That said it's presumably better than what you currently have.

I've no experience of Blackjack, so can't comment.

Good sketch btw. (y)
Yes that did cross my mind. But I was planning on using the first row of ties starting just above the dpc. I presumed the first 6/7 rows of bricks below the dpc would be ok without any ties.
Any thoughts on what would be the best vertical DPM to use out of the 3 options above?
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Ive decided to go with Liquid DPM painted on the inside of the external leaf.

I have another question which i'm hoping someone can help me. I need to run a soil pipe through this wall (above the external floor level, but below the DPC level). I know I will be penetrating the vertical DPM, but I wanted to know what would be the best way to seal this penetration in order to keep the water out and to ensure the vertical DPM stays fully effective?


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