Replacing a DPC

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Manchester
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Hello all,

About 18 months ago I got around to gutting my living room because it really needed it. I took the walls back to the brick and then dry lined it and skimmed it. A few months later I started to see damp patches along the base of one wall. This got worse over a period of a couple of months and some minor damp patches were beginning to show on a couple of other walls. I think I have managed to damage the DPM whilst removing the old plaster. The DPM was the original one and the house was built in 1951 so it's a good age.
My first attemp at correcting this has failed miserably. I used DryZone last May or June but, with the rain over the last month or two it's obvious that it hasn't worked. I am now planning on removing a course of brick and replacing the DPM. I have spoken to a builder that has done loads of work for my old man over the years and he has told me that it can be done but it takes time. He actually did this job for 3yrs at one time for Manchester council so he should know his stuff. He explained that it's done by removing 3 bricks and then leaving the 4th one in then removing the next 3 and so on. Then you can replace the 3 that have been removed on a bed of mortar along with the DPM. Once these have set you wedge above them with slate before replacing the brick that was left in and then pointing it all up. This all sounded great until I went away and thought about it and realised that this would mean overlapping the DPM. Is this possible, surely the fact that it's overlapped will mean that damp can get through. I can't speak to the fella that told me this cos he's working away in a sunny place for the next few months the stuffy bugger.

Hope this explains my problem clearly enough, if not let me know and I will try to explain in more detail

Thanks in advance of any replies

Peaee
 
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could it of been condensation when you dry lined the walls?
are the walls cavity?if so every 18" - 2' make a hole through the wall about 2 bricks wide and high and clear the cavitys from the inside,it could be that with all the rain youve had the dpc has been bridged.
 
Gregers,

They were my first thoughts but, I did it during fairly warm/hot weather so that kind of rules out condensation and the bridging theory doesn't hold up cos one of the walls is a single skin. I think using the power chisel to remove the old plaster has caused enough vibration to damage the original DPM, more fool me really, I should have took my time and removed it the old fashioned way!
 
single skin,external wall?or internal?check the pointing etc,maybe spray with a grangers type fluid to repel the water.
wouldnt think what type of weather you had when doing the job did you think about installing a moisture barrier?condensation will happen when the condidtions are right or wrong,and also consider air flow.
 
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The single skin is internal. The damp only reaches a certain height which os why I'm fairly confident that it's rising. Also the house is well heated and I'm not shy when it comes to keeping the place warm.
 
I did mention in the first post that I have done this on one wall and it's failed. I don't want the bother of doing it all and having it fail on me. I would rather do the job properly and then I know it's done. Don't want it coming back to haunt me in 18 months when I've redecorated the place. I just need to know the technique for replacing the physical DPM and wether it'sOK to overlap it.
 
Were not talking a small river rising up through the brickwork here, if any did manage to it would be minimal, overlapping will be fine, kind of like long runs of lead flashing, made up of multiple peices.

I guess it could be done with one bit, but it would be slow going, remove three, replace the first one, remove the next and so on.
 
Overlap is fine ...saw this done by an old boy when I was apprenticed 1973...as you described.
 
i know you said it in the 1st post,why not try a spirit based fluid rather then redo using this cream?
 
I don't know really. I suppose having had one chemical traetment fail on me has made me wary. At least if I physically replace the DPM, I know it won't fail, cos it can't.
 
Chemical DPC's don't usually 100% stop the damp, but slow it down. It really needs to be backed up with a sand/cement render with added waterproofer/salt retarder. BRE do advise the use of this method, although they do state that a physical DPC is the best method. You can lap the DPC, as this was done on site with the older type rolls as they were much shorter.
 
We always used to overlap by at least 4 inches. The damp won't penetrate the overlap.
 

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