I live in a 18thC terrace cottage. All out walls are single brick with an internal block skin. The party wall is still single brick. We have recently lining papered and painted the lounge that abuts the party wall. Before we papered we noticed a skin of thick paint on the wall that had a rubbery texture. For the most part we just papered over this, but where we removed the dado rail some of it came off. We have since seen discolouration of the wallpaper about 1m up the wall and runs in a horizontal band about 10cm high and about 2m across.
The guy next door has a chimney that is directly behind this wall. It is not currently working as he is in the process of renovating the property.
My assumption is that damp is either rising up and coming through. Or there is a problem with the chimney lining and water is dripping down. Either way is is affecting our wall.
So I suppose my questions are:
1. Does this sound like a damp problem?
2. As it is a party wall and is essentially his chimney that may be causing the problem is it his responsibility to fix, and to what extent is he obligated to carry out works to a party wall that is affecting our property?
You need to find out whether a dpc has been added with concrete rendering up to 1+m.
If the whole ground floor has one (including the party wall) then your best option is to add more rubbery texture paint to the dado rail area.
If a dpc has not been added you could consider having this done to the party wall.
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