Our house dates from 1850. A stretch of ground floor hallway wall has been damp ever since we moved in 5 years ago.
The wall is a mixture of brick and stone with no damp proof course. The area outside is a small courtyard belonging to our neighbour (not accessible from our property). Every time we get a lot of rain, water gets trapped in this area, then we notice that the walls feel damp especially at the bottom. Paint has flaked off and brass coated sockets have corroded.
A damp and timber report carried out when we moved in suggested that hanging baskets were to blame (hung on the wall by our neighbour). This does not seem likely as the damp is mainly at the bottom of the wall.
The advise given was to replaster.
So we did! Guess what.....the paint is flaking again. Any advise on what we really should have done is very welcome.
Like previous reply more information needed but gut feeling is that your neighbour paving is too high against your wall, usually external ground levels should be level with the solum or the ground below suspended floor or below the concrete of your concrete floor.
They either have to lower their levels, potentially put in some form of drain to remove any ponding water.
You can then have a proper damp prroof course installed and there levels should remian at least 150mm or 6 inches below your dpc, unfortunately you may have to have plaster removed.
You could look at tanking the wall, but honestly drop levels!
Sorry I can't provide an exterior photo (the window from which I could get the picture has a swollen frame and won't open at the moment).
But in answer to the questions:
There is a suspended wooden floor
The exterior ground level seems ok. It consists of exposed sandstone at ground level and pointing appears ok.
The wall affected by damp is approx 8ft long. There are two air vent bricks at one end of the wall (the damp here is minimal). The other end of the wall has no vents - and what I should have mentioned before - it is right next to our cellar. Our cellar has not been tanked so I wondered if the damp was spreading from here?
There is no sign of mould or black spots. Just flaking paint, soft plaster, and a corroded socket. There is also an occasional trickle of water down the wall after very heavy rain.
I've been told (not by an expert!) that a chemical damp proof course may not solve the problem - but replastering (with some sort of damp repelant substance??) may be the way forward.