I have a lounge that has one external facing wall which is getting damp on the inside of that wall. The entire room was replastered about 6 months ago and since winter began it has now started to get damp with a bubbling effect and black mould on the inside wall.
The area on the outside of the wall is not concreted and I have dug away about a foot deep below the surface then painted the wall with a Damp Proof membrane hoping that when it rained the water would be below the dpc which is probably non existant in an old 1920's house.
Presumably where i have dug away has actually made it worse and the water is collecting in the furrow then been drawn up the wall.
From your description what you have done is to form a membrane at low level on the wall and any water getting into the wall at higher level is now forced inside. Can only suggest you treat the whole wall with a few coats of silicone dampseal to stop water entering the wall.
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