Hi, I have a problem with damp in one of my rooms, the main part of the house was built in the 1700's and an extension was built in the late 1800's early 1900's. The damp is occurring on an internal wall adjacent to a bricked up fireplace in the extension. the wall behind where the damp is occurring used to be an old fireplace to what was once the original kitchen to the house (this fireplace is now blocked up). We have an internal flood (washing machine) in the main part of the house a few months ago and this damp patch appears to have started then. The walls between the extension and the original house are a couple of feet thick, solid stone walls and there is a cellar below the 'extension' which is dry. The walls in the extension have been skimmed with modern plaster over what I think is the original lime plaster.
I have had one builder tell me it is rising damp which I don't think is the case. I suspect either some water has got through from the flood and penetrated the wall somehow and that water is trapped behind the plaster or the damp is coming through from the old kitchen fireplace.
Would you suggest removing the plaster from the wall and seeing what the damp is like behind the plaster or shall I open up the blocked up fireplace to see if there is damp there?