I have had an on going problem with darks marks that won't seem to go away. These marks are not wet, greasy or even colder than the rest of the wall, you can simply just see them. They were improving and going away but have recently appeared again (Not after rain, just generally cold weather). The never grow or change in size or appear any darker than they originally did but they have just reappeared in the same place. The area underneath and to the left of the beam is plasterboard, to the right is the chimney breast.
We have had various work completed. :-This started off with having the wall taken back to brick with a salt neutralizer adding to the brick and left to dry overnight. A plaster coat applying to the area that was stripped back to brick and then a skim coat applying to the chimney wall and plasterboard area connected to the chimney wall. :- We have had the chimney repointed, chimney cowl checked and confirmed there is no problems, lead flashings and underfelt completely redone around the chimney. This appeared to solve the problem but it has shown again in the exact same place. (I have had 5 separate roofers check the work who have all said how well the work has been completed and they can't see any problems.)
Does anyone have any idea what this could be? (a leak still, condensation, salts somehow still (Despite the salt neutralizer).
Hi hoyle23, Suggest you start by checking the wall and dark areas with damp meter. This will give you a good indication as to whether it's soot staining leaching through the wall. If the wall is dry then paint it with a stain block - spirit based not water based, oil based undercoat is fine provided the wall is dry.. Regards, stoneyboy
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