Hi, About 6 months ago, I got a damp proof course put in. The walls were tanked (over 1 m high) with tanking slurry plus base and top coats of sand and cement with water proofer (sika 1) were applied. I've now painted on the mist coat (watered down Dulux). The dpc seems to have worked, as the exterior walls are almost completely dry (though there are a few blotchy patches of damp – roughly one small patch per wall – where the mist coat is darker than in the dry areas). The main problem is that on the two internal walls (either side of the stairs), there are multiple patches of damp all over the bottom 1 m of the wall (where the wall was wet due to rising damp). The damp patches don't start at the bottom of the wall and go up. Instead, the damp is in blotchy patches on one of the walls, and in more of a band on the other one, which you can see in the photo (though it's not a continuous band, and there are still blotchy patches, e.g., one a few inches from the ground on the far right of the wall, not in the photo). The downstairs rooms all have floorboards (no cement next to the two affected walls). The other side of each of the two affected walls (the walls of the cupboard under the stairs) seems fine – there was some salt coming through the mist coat, but no damp patches. The damp proofer/plasterer who did the job came back and isn't sure what's going on. He suggested painting the next coat and the top coat, as it might be that the affected patches are just cold patches on the wall. However, some of the mist coat had already began to peel, and when I painted over it, that coat too began to peel in places due to the damp. (Btw, the patches are damp to the touch, but his damp metre apparently wasn't picking up any readings of damp, so I'm not sure how to interpret that – he said the metre gave readings for the top layer of plaster.) I don't think the dpc has necessarily failed, but I was wondering if anyone knows why the damp patches have occurred given that the plaster is supposedly protected by the tanking/water proofer. And why does the damp occur only in certain patches? Please let me know if any more details would be helpful to work out what the problem is. Thanks for your help.