Damp Proofing

Dampness under carpet along length of external wall.

Anonymous user 16/03/2024 - 2.52 PM

## We are in the process of redecorating a room in our house. The room has two external walls. One short one with a window and radiator, and one longer one. When we took the carpet up, we noticed that the underlay under the carpet was damp all along the length of the longer external wall, and the wooden carpet grippers were rotting and mouldy. The surface under the carpet is some sort of tiling, and likely sits on top of concrete (I’ve been told this is fairly common for places built in that era (1970s/80s)). There is no visible sign of damp in the skirting boards or the wall itself. On inspection of the outside section of the wall, there do appear to be some large patches of damp going up the wall, as well as some patches of white on the brick itself (assuming maybe mineral deposits?). There is a roof terrace belong to a neighbours flat above the room. The patches of damp appear to reach up to roughly the level where the roof terrace would be. I’m of the understanding that the wall is a cavity wall and that the pipe that drains the roof terrace runs through the cavity and into the drain beneath, and that it is roughly in the location that the patches of damp coming through the bricks are. I suspect that this is the source of the issue, but if this is the case, I’m confused as to why there are no signs of damp on the exterior wall / skirting boards. I’m far from an expert in the area though. Was hoping someone could provide some advice.