Mystery soot ingress

[jb2410]

Hi all,

Noticed some soot like dust lying on our mantle randomly the other day.

Removed the mirror and the wall is covered in what I am possibly wrongly assuming to be soot underneath?

Assume this is a damp issue of some sort causing this, just confused as to how it’s coming through the wall - Staining I would understand at least!

Happily I am looking to redecorate in the not so distant future and want a log burner in with flue liner etc instead of the almost never used open fire, but how do I actually fix the plaster issue to stop the soot leaching through again?

The wall was painted with some stain block stuff before this paper went up but that evidently doesnt seem to have done the job.


Cheers for any advice

[sherman]

Best solution will ve to strip the wall back and replaster.
You have a cold damp wall. You need to reseal the wall.

[essayer]

Not sure soot would get through a wall and wallpaper.. looks like mould to me. clean it off and see if it stays gone while the mirror is removed?

[jb2410]

Thanks folks, it’s quite dry and powdery which is what made me think soot but yes mould would make sense too!

Whichever it is I brushed it off earlier so will see how quickly or if it returns. Must admit I hadn’t considered damp properly as it’s not an external wall but could be coming in through/down the chimney I am sure.

Not the end of the world as there will be plastering needed once the stove goes in anyway.

[paulwirral]

Best remedy is old school , strip the existing plaster off and re render - plaster with sand and cement with a damproofing additive in the mix then plaster to finish .
Make sure the existing chimney is vented bottom to top .
I speak from many chimneys and fireplaces experience.