Damp Spots Coming Through Screed - What to do?

[kcdionysus]

Hi all. I'm new to here but have picked up some good information from other threads but need a bit of specific advice.

We purchased a house and are in the middle of refurbishing it. The kitchen was tiled previously and had tiles that were cracked and had lifted really high in places. I pulled them all up and found that the screed had crumbled and popped underneath. The mix in these areas did look a bit sandy to be honest and I believed it to be just badly mixed at the time. These busted areas tend to be close to the walls as opposed to the middle of the room.

I planned to use a 'deep base' leveller for these areas as they were of varying degrees of thickness, then a thin self levelling coat over the whole floor before tiling. But once I had hoovered the areas out, I could see small damp patches beneath....maybe an inch or so diameter in each 'hole' that look like the source of the problem. I also cannot see any evidence of a dpm as the screed looks like it was laid straight on a rough concrete slab. The house was built circa 1970.

The question is - can I repair/fix these areas locally and stop any damp from rising up to bust the levelling compound/tiles in the future? If so, what could I use to stop the damp rising? Would painting a liquid dpm over the patches work to block the damp with maybe some sbr mixed into a wet mix screed poured in to fill the holes?

Or do I need to lift the whole floor screed and re-do it again? If so, what's best to put down as a dpm over a fairly rough concrete base before screeding?

Any help/advice would be great.

 

[Bubblecraft]

Welcome to the forum

 

[Dale44]

I would consult a builder to make sure, but don't try doing patch work, the damp will work it's way out somewhere. Sounds like a full DPM is needed.

 

[Ajax123]

If there is rising damp a liquid DPM is not likely to be suitable. It will probably need a proper tanking membrane. Uzin ltd do a system wich is a levellernd tanking system in one I beleive. This might be an answer. Alternatively possibly an uncoupling membrane may be the answer.

 

[kcdionysus]

Thanks for the replies. The 'uncoupling membrane' is something I hadn't heard of so I read the stickie put on by Dave and it looks like a great system. A bit pricey though but if necessary, I can see it being really good. Are there other manufacturers other than Ditra that are maybe a bit cheaper?

Having looked more at my problem, I dug a bit more screed out and I can see the dpc on the brick walls is slightly higher than the existing floor. This is possibly where the damp is coming up the walls and hitting the dpc so spills over and connects to the floor?? Based on this, I reckon there could be an alternative solution but I'll get hold of specialist and see what they say.

 

[Gazzer]

If there is rising damp a liquid DPM is not likely to be suitable. It will probably need a proper tanking membrane. Uzin ltd do a system wich is a levellernd tanking system in one I beleive. This might be an answer. Alternatively possibly an uncoupling membrane may be the answer.

Any more details on this product ?