Damp patches on party wall

[Davet1]

Hi folks, I wonder if you would be kind enough to offer some advice?

My wife and I are in the process of buying a house built around 1890. The survey reported damp as an issue, so we've taken a look for ourselves. The ground floor external walls are bone dry inside and out, but there is a fairly large section of damp (noticeable to the naked eye in discolored wallpaper, though not really to touch) at the bottom of the party wall in the dining room, about a foot high and maybe 3-4 across. There is no obvious cause in the room (no visible pipes etc) and no visible issue with the same wall upstairs. We had a word with the neighbour who said he was occupying his Dad's house, and he thought there had been some damp in there that had been fixed, though he couldn't be specific.

We're just wondering what to do. Could the damp be residual from this earlier problem, and could we get around it by dehumidifying the room? Or as it's presumably come through from next door, are we likely to need bigger, specialist repairs? The house doesn't seem to have a DPC due to the age, but as I said the outisde walls seem fine.

I'd appreciate any help you can give as this is our first non-rented property and it's all Martian to me!

[stoneyboy]

Davet1,
Most likely rising damp and for such a small area it's probably leaving and see what happens in time.
end

[Davet1]

Thanks Stoneyboy. We're being advised to get a damp survey. Probably going to push back on the vendor - don't see why we should pay to investigate a problem with a property we don't own yet - and may not end up buying depending on the outcome.

[Detective]

Party walls can hold damp for some time especially if the walls are painted or have washable wallpaper. Is there a chimney in this wall?