Damp patches on chimney breast.

wazza99

another shot

wazza99

This is the interior of that actual wall where the damp is emanating from.

Boat_to_Bolivia

No expert, but that looks like patches from condensation.

If the walls were painted before completely dry after condensation ran down them, then you will get patches like that.

Just my opinion of course..but my bet is a condensation problem rather than a leak or fundamental damp problem.

Slinky

We had problems with damp patches on the unused chimney brest. We had the pot capped, but still had problems, came to the conclusion in the end that the pot was very short and heavy rain hitting the flaunching was bouncing up under the cap and running down inside of the chimney. The builder at the second attempt removed the pot and cemented a slate across the top of the opening which seemed to stop it.

ETA he could try drawing round the patches to see if they are increasing in size.

wazza99

Well after todays relentless rain, the patches are no more wet than before, if anything drier ! so i think i can rule out external water ingress. Im going down the condensation/salts route. Dehumidifier will reside in room for a few weeks see what effect that has, then maybe repaint with a barrier paint then either repaint or paper.