Damp stone wall

We have a wall in our sitting room which gets wet when it rains. It is a party wall with our neighbours house, they do not have a problem. It is a stone wall and only the bottom half gets wet. We have been tested for leaks and there are none so suspect a water course of some description that fills up in the rain. When it dries out we have flaking plaster to deal with. Any thoughts?

I think you are right John. I wish the walls didn’t look so different though!

Hmm, a tricky one Helen as it's the almost clasic mortar dusting you get with rising damp. The floor looks good enough to be on some kind of sub floor rather than earth. I am not sure though so difficult to give any real answer. Your neighbour may not have the problem if they are resident all the time as they can evaporate any damp away as you do after a few days.

Sorry John, here is the offending wall! The first photo is the good one!

Hi John. Attached 2 photos of the wall, the damp one (now dry because we have been here for a week with heating/fire on and no rain) and a dry one. They are either side of the fireplace. As you can see the floor is tiled and I beleive the floor underneath was just a dirt one. We don’t have a cellar so built straight on the ground some 300 years ago. The flaking I refer to is the stuff inbetween the stone, looks lie a beach after a week or so!

Helen, when you say you have flaking plaster, can we assume without a photo that the wall has been plastered/rendered at some point? You are correct in trying to locate the source of the damp, what are the stones, limestone? Limestone does soak up water but is also very good at evaporating moisture away providing it can breath to do so. Modern plaster may impede this. A coat of lime plaster/render on the other hand will allow the water to evaporate away.

What is the floor made of? It is quite common for concrete to be a poured floor in old buildings and that to prevents evaporation so the damp under the floor will find a point where it can make it to the surface.

It is not easy without knowing more or having pictures.