Upstairs chimney breast damp/staining?

[ginberry4]

Chimney breast in DS’s room has many damp patches / staining which are not wet to the touch but certainly look it.
The fireplace/chimney had been blocked downstairs with no ventilation for a number of years, this has now been fully opened and swept (it was also heavily birds nested). It is also ventilated in DS’ room. The chimney stack has a vented cowl on it which the chimney sweep said is the correct fitting to allow airflow and prevent rainwater getting in. We’ve had the pointing inspected on the chimney stack & external wall & this is due to be repointed in the next few weeks.

There is no guttering or pipework on that side of the house so no other place water can be getting in. I think we’ve done everything we can to resolve the problem externally - so now just want to know how we can get rid of these patches internally. If anyone has any suggestions it’d be much appreciated. Thanks

Chimney breasts need ventilation

If they’ve been blocked a vent needs to be fitted.

See at our house there is absolutely no water source above it. It’s the gable end of our house, there’s no guttering or pipes, no bathrooms or boilers. It’s been re-roofed, the chimney was all repointed, lead flashing re-done, etc etc. The pointing is lime, and has been repointed where the builders said was necessary but maybe it’s failing more than we realise.

We have a dehumidifier running in there constantly, my son keeps the door shut all the time which doesn’t help & could well be the cause but he has a lot of Lego & we have a very stupid cat that would/does try to eat it if it gets in there so not much choice on that really. Window is open for ventilation as much as we possibly can.

Ours was salt damp.

We used a salt neutraliser on top of plaster but it didn't work so we stripped off the plaster and are in process of using tanking slurry to cover the bare brick. Then we'll reboard with a foil backed plasterboard to create a moisture barrier and replaster.

We're the same as you, absolutely no chance it's a leak so we worked our way through a list of possibilities.

Loads of videos on YouTube, DampSam explains it better than I can.

Good luck!