We have 3 or 4 small patches of damp just below ceiling height on the wall above our solid fuel fire. I have uploaded some pictures - you can just about see the patches below the cornice to the right of the window. They were there when we bought the house 10 years ago and we put up with it, but recently I think they are getting worse. The chimney breast is external and we have recently had the chimney stack repointed and the flashings looked at. We also have a U.F.O MKII chimney cowl fitted (mounted for solid fuel). I am therefore assuming the problem is unlikely to be external rain penetration. I am left thinking it is condensation within the chimney. If we get a burst of heavy rain the patches get darker and then slowly lighten up as they dry out. We don't use the fire much so I suppose it is not regularly 'dried' out from inside. Do we just put up with it or do we go down the expensive route of having the flue lined? Any advice would be most welcome. Thanks
Thanks for replies to date.
Update as follows: General consensus seems to be the patches are due to hygroscopic salts drawing in moisture when the weather is damp. I have had a damp proof specialist round who has said he will remove plaster etc to a suitable depth in order to be able to cover the relevant area (from the window on the left to a width of 1.5m to the right, under the cornice and above the dado) with a damp proof membrane to stop any further penetration from the salts. He will then skim over the top. I am concerned this will just 'move' the problem and make the salt penetrate somwhere else. I just don't want to make the problem worse. Please help!
Read more: http://www.diynot.com/forums/building/damp-stains-on-chimney-breast.379258/#ixzz2j11hFWd6
Thanks for replies to date.
Update as follows: General consensus seems to be the patches are due to hygroscopic salts drawing in moisture when the weather is damp. I have had a damp proof specialist round who has said he will remove plaster etc to a suitable depth in order to be able to cover the relevant area (from the window on the left to a width of 1.5m to the right, under the cornice and above the dado) with a damp proof membrane to stop any further penetration from the salts. He will then skim over the top. I am concerned this will just 'move' the problem and make the salt penetrate somwhere else. I just don't want to make the problem worse. Please help!
Read more: http://www.diynot.com/forums/building/damp-stains-on-chimney-breast.379258/#ixzz2j11hFWd6
