I have damp coming through an internal floor and will be removing the concrete floor totally as it has neither insulation nor a membrane. The property was built approx. 1800 and has a slate DPC, but it has broken down. We are planning to have a chemical DPC at the same time as the floor comes out. The new floor will be below the new DPC assuming the DPC is 6” above ground level. When the new floor goes in, it will have a damp proof membrane installed as well as insulation etc. The question I have is what do I do with the exposed end of the membrane above the floor? I have read on this site I can ‘Tank’ the walls, I assume I do this before laying the floor, but it still leaves the gap between the membrane and the ‘Tanked’ wall as a potential route for the ingress of moisture.
I am thinking I should rake out the mortar just below where the DPC has been injected and tuck the membrane in? In the same place as the membrane would be laid if I were building a new house. This would seem logical and I assume would do away with the need for ‘tanking’, but I am concerned as the best I can hope for is 15mm penetration of the membrane into the mortar of the 9"thick wall, rather than the membrane going all the way through the course of bricks? Is this enough or am I barking up the wrong tree?
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