We've lived in our 1900 terrace property for over 3 years and have not had damp problems to date. At the beginning of last week we noticed a fairly strong odour when we came home and on Friday we noticed black mould appearing on the adjoining wall with our neighbour.
The mould is in the centre of the wall and is at the top near the ceiling; so far we have not been able to catch our neighbours in to establish the root cause.
We have no pipes in this location, they run through the centre of the house and as it's an interior wall, we do not think this can be down to a leaky gutter.
The neighbours only moved in 3 months ago and shortly before then the previous neighbour installed new furniture in the bathroom, (including a very noisy jacuzzi bath :x ). The wall with the damp problem is situated directly below their bathroom. Is it possible that a leak on their side could be causing the problem?