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Damp proof course


pogo
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I have a concrete barn floor which allow damp to rise through it.I was thinking of putting down a plastic DPC,as normal,but wont want a thick screed over it as I don't want to lose valuable height. It has been suggested that I could use bitumen pate,painting it on carefully to cover EVERY pin hole,and then a thin screed,or self levelling compound over it.What do you think,any alternatives,or stick with the plastic dpc?

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[quote user="pogo"]I have a concrete barn floor which allow damp to rise through it.I was thinking of putting down a plastic DPC,as normal,but wont want a thick screed over it as I don't want to lose valuable height. It has been suggested that I could use bitumen pate,painting it on carefully to cover EVERY pin hole,and then a thin screed,or self levelling compound over it.What do you think,any alternatives,or stick with the plastic dpc?
[/quote]

I will give this a go, based on experience, not qualifications;

I wouldn't put a thin screed on a membrane, because it will break up rather too easily. Membranes on concrete have a habit (IIUC) of leaching water into the walls at the extremities. I have seen some disasterous results of painting Aquaproof or similar onto stone.

I believe that the only way you can solve your problem is at source, rather than masking it. Dig out the concrete and a) build a dwarf wall with a suspended floor or b) arrange a drain and a floating concrete pad (plus insulation and DPC).

 

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By coincidence this runs very closely with a recent thread by gluestick. I had a very similar situation about 20 years ago. It was a good but sloping concrete floor to on open veradah which I was replacing with a conservatory. Height was at a premium.. I gave it two coats of some sort of suitable bitumen solution and then screeded it and finally laid quarry tiles. The screed as far as I remember ran from a minimum of about 1 inch to about three inches (to remove the slope). It is still absolutely solid with no hint of separation after all these years and despite some very extreme temperature changes.

Nevertheless I feel that I "got away with it" but I wouldn't do it on large floor area of a habitable building. You say your concrete lets damp through. Good well specified concrete is really pretty waterproof stuff and I wonder whether it would be better just to start again, depressing though such a prospect may be.

bj

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Sorry, this mght or might not help, in England i used to use a substance called Ventrot, like a bitumen but melts at a lower temp, compaired to normal flat roofing bitumen, and the floor or roof must be primed first. Then you can put a thinish screed over this ( 65 -75mm). Then tile or whatever. You will need a tar burner for this,as the bitumen comes in solid blocks which you have to break up to fit in the pot.A lot of work but will do the job.A roofing firm whould be your best source, if they do flat roofs hear. (not seen many )
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Hows this for a possible solution to your problem there are semi-rigid plastic mats designed to be used on top of wooden floors which are to be ceramic tiled.

While these mats are used for their slight flexion the idea being that ay residula movement in the timber once screwed down will be masked.

The mats however are plastic therefore may provide your dpm and tiling solution all at once?

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hi

 ok yes you can , but the floor must be spotlessly clean first. paint on the first coat with a roller and then second coat it the same ,but throw in some sharp sand as you go this will give a key for the top layer ...say tiles, screed or flaggs ??

             Dave

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This sounds like the black stuff we used to waterproof our house last year, the stuff I described to Gluestick, and it has worked admirably because the place was riddled with damp due to the earthen floors. Of course we still have a bit of residual damp in the place which is only to be expected as we are not in residence yet, but we no longer have the delightful black spotty effect on our walls and the floors are now flat, even flagstone tiles.

.

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