Wall tanking - whats supposed to happen at the edges? (pics)

[chrisu]

Hi, a wall in my house is partly below ground level and so has, I believe, been tanked. I hope that is the correct term for the ridged brown plastic sheet that has been built into the wall between the damp bricks and the internal plaster. This seems to be working OK in most places but at the bottom the the wall the damp is getting through.

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• chrisu
• 1 Sep 2008
• 1

I used a small chisel to get through the surface layer and could see the sheet stopped about an inch above the floor. Once inside the wall it was easy to scoop out the damp sand to see the back of the bricks

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• chrisu
• 1 Sep 2008
• 1

It seems obvious to me that something proper should be happening at the bottom of the wall - but What ?

Thanks in advance for any ideas (even whacky ones)

 

[FreshAL]

I don't have a clue what needs to be done there, but if no-one pops up here with a solution, I do have an idea.

I had 3 separate damp-proofing specialist companies come to my flat and quote (free of charge) for the work. They were all happy to discuss the problems in detail. In the end I went with a firm who were happy to work out between us which bits I could do and which bits they would do.

Can't hurt to get someone in to have a look for free.

 

[kevintaylore]

It looks like a cavity drainage plaster membrane - e.g. http://www.newton-membranes.co.uk/newlath.htm or http://www.safeguardeurope.com/products/oldroyd_p.php

These are normally tied into further cavity drainage membrane laid under the floor. Additionally, in basement systems, there is usually a drainage channel at the wall-floor junction - as per the following CAD drawing http://www.safeguardeurope.com/cad/XV-001.pdf

 

[^woody^]

Any tanking has to be either continuous and sealed around the wall/floor junction, or there would be suspended floor and a sump pump to remove water below.

It really depends on what system was installed

 

[chrisu]

Hi, thanks for the ideas.

"It really depends on what system was installed" - I think the problem is that NEITHER was.

A link suggested lead me to this http://www.newton-membranes.co.uk/baseboard.htm which is basically a drainage channel hidden inside a skirting board which looks like just the job.

Chris.

 

[kevintaylore]

That would probably work. Another option (provided that you have enough headroom) is to lay the normal drainage channel around the perimeter of the room and fill the gap with 50mm insulation board. With either option you still have to make sure that the drainage channel drains to a gravity drain (e.g. in the case of a house built into a hillside) or a sump and pump (in the case of a full basement).