rising damp caused by damp proof concrete floor

[peggowski]

It's really unusual to get rising damp on just one wall, especially when it is an internal one

You don't think the house has had a damp proof course some years back and that one wall was missed do you?

no sign of a dpc being installed at any point, especially as it is 2 foot thick walls with rubble infill i would guess! its stone built and at least 200 years old, possibly as much as 300 years old.

[stuart45]

The old flag floor use to breathe or if you like let the damp out into the air, now its sealed the water is coming up the bricks.

Spot on. A common problem with old cottages. People are now starting to realise that the floors and walls need to breathe as their construction was different to a modern house.