Damp on internal wall in Georgian flat

[Dampquery100]

Hi there,

In my basement/ground floor Georgian flat, I have a large patchy damp area. It is in the basement, but on an internal wall. The external walls have been damp-proofed. It is a really odd shape, and does feel cool to touch. There is a picture attached. Does anyone have any suggestions what could be causing this? And how it should be fixed? Also, should this have been flagged as an issue in my home buyers survey?

Thank you! View media item 67635

 

[Dampquery100]

Help! Does anyone have an any advice on what might be causing it? The area of damp has definately got bigger....

 

[OwainDIYer]

does it correspond to a disused fireplace?

 

[Dampquery100]

no i dont think so, the fireplaces are all on the other side of the house. The other side of this wall has a bookshelf and opens into a hallway and staircase..

 

[tony1851]

Could be a number of reasons; you say the external walls were tanked, but were the internal walls done as well?
Could it be condensation?
Water-absorbing salts?

 

[pinenot]

Look for a leak, in an internal pipe or is the wall directly below something carrying or using water? Also the damp patch is not showing up very well in the image you've posted...pinenot