Any help / advice here would be greatly appreciated. I have just bought a c.1900s terraced house and at the top of the stairs on the left where the wall adjoins to our neighbour's we have a damp patch about half a metre square. The damp also continues on to the wall which has the bathroom and basin behind.
My immediate thought was that the basin was leaking somewhere but this does not appear to be the case.
My second thought was that it could be a problem seeping through from next door. I had a word with the neighbour and he mentioned his bath. This made me think that he's probably had a problem with it before. He then said he'd get a plumber out to fix it. This has now happened but the damp is not drying out.
Could water be getting between my house and my neighbour's terraced house and if so where could this be coming from? What other signs should I look out for in order to ascertain the cause of this damp?
Please bear with me as I am entirely new to DIY!
Many thanks, Paul.