Having just moved into a new house, we have stripped most of it back to basics, and under the wall paper on the lounge chimney breast discovered some damp patches.
The chimney is strange that it obviously used to be a large arched opening (you can tell by the brick pattern), but has since been made smaller and concreted to make it square. In adition to this a secondary reduction of size was done by adding a moulded fire back thingy (excuse my lack of technical terms)
We took out the moulded piece by breaking it into pieces (the only way), and have taken the opening back to the larger but still reduced from the original opening.
We also then discovered that to the right of this opening, there was a second, smaller opening that had been bricked up, which when we took out a couple of bricks reveled another chimney.
We think this secondary opening would have been an old bread oven or something similar (the house was built in 1898 by the way).
By using our video camera, we looked up the secondary chimney and found it had been sealed at around ceiling level with a concrete slab of some kind.
The symptoms are that after rain (and only after rain), these damp patches appear on the wall around the top of the fire opening.
It's hard to describe, so I have inserted the image below.
What we have done is added a sealing cowl to the unused secondary chimney pot, and an anti-downdraguht cowl to the used open fire chimney pot. We have ensured the mortar on top of the stack is not cracked by replacing it all with fresh. The flashings around the stack on the roof have been repaired and where the roof slates didn't meet the chimnery stack, has now been fixed.
However, we are still getting the damp patch, and are at a loss as to why.
Can anyone ofer any advice please?