Our builder came in to hack off damp plaster which has been an ongoing issue since we moved in, we chose to wait and do this as part of a kitchen renovation.
We found behind the damp plaster, that the original slate damp proof course is about 3 courses of brick above the floor level. With no damp proof course in the section of the wall that used to be the chimney flue. This has caused water to bridge the DPC and cause the bottom of the wall below the DPC to be sopping wet, with the bricks and mortar now in quite bad condition.
Over the years, this has been treated in various ways by the previous owners, including a membrane run under the floor tiles, tanking various sections of wall and even putting a border of tiles to waist height on OSB with roofing felt behind it!
Our builder has recommended tanking the entire wall, with SBR/Sand and cement render and then plaster over, but we can see that the brick where the wall has been tanked has begun to crumble, this is bad enough to mean one wall will need to be rebuilt.
The damp wall is a party wall (several houses built like this), so doing anything just on our side, probably won't resolve the issue.
This isn't our forever home, so we're keen to do the right thing, but without bankrupting ourselves in the process.
Any advice on what to do to keep our kitchen dry, would be much appreciated.