Q. Since we moved into our house over 3 years ago we have suffered from 'water ingress' into the first floor bedroom.  Subsequently we had the chimney lowered and the roof done as we feared this may have been the cause. Some, but not all of the plaster on the offending chimney breast was hacked off and replaced. Since then, however, it would seem that the plaster has remained wet and stained despite our assertion that the water leak has gone away. The stain manifests itself through the cornice and the ceiling too. I would be interested in your opinion as to whether you think this is a hygroscopic salts issue caused by the fact that the chimney breast was re-plastered too soon without being allowed to dry properly or whether an application of a primer-sealer type product will help. Would a solution be to hack off the plaster again, allow time to dry and re-apply a lime based plaster?  Would this preclude the use of an emulsion paint finish? Having suffered this stain/wetness problem for many years and having sought many people's advice it has become somewhat of an enigma. Can you advise please??

Submitted by: DA 

A. There is a strong likelihood that any moisture ingress that has occurred in the vicinity of a chimney will bring with it hygroscopic salts which are abundantly present within the flue as a result of burning coal. You do not state a time scale of the events so it is difficult to advise with any certainty. Read this article on our web site and in particular the section titled 'What price a correct diagnosis?' as it sounds like what you have may be a similar tale.

There are ways to cover the problem if salts are causing it. It the newer plaster as badly affected as the original plaster? Does the intensity of the visible dampness vary subject to weather conditions? The cornice and ceiling plaster are also likely to be salt contaminated.