4 damp chimney breasts but only in certain areas

[asbo2010]

Help please, I have a chimney which runs up through the house which has the living room/ dining room back to back and two beds above back to back. All 4 of the fireplaces are open and the flaunching and re-point etc has been done on the top. The problem is that in each of the 4 rooms there is an area on one corner only of each and just at ceiling level down approx 12" which is damp. The damp meter shows this but the remainder of each breast is fine. There is yellow staining on each. The levels of damp have not changed over the last year and it does not seem to be affected by rain. Also the chimney where it goes through the loft into the roof is fine according to the meter readings. Does anyone have any ideas what is causing it and what I can do about it. I really want to decorate but seems pointless at the moment.
In addition I have a wall at the bottom of the stairs in the centre of the house where an area at the skirting approx 6" square is extremely damp. I am about to have the floorboards up to run a heating pipe (not one there at mo). Can anyone tell me what I am looking for as the cause here? seems odd that not an outside wall and only a very small patch. (only noticed when the wallpaper lifted)
Any help appreciated as only a simple girly!! Ta.

 

[asbo2010]

not sure if this makes a difference but my house was built in approx 1890 so the interior walls are the traditional lathe and plaster and the damp proof slate on one of the walls has been breached but it is approx 15ft away from the interior wall (and chimney) and I cannot see that there is any problem up to the point in wall with the damp at the bottom. This wall is also side on to the outside wall where the damp proof is knackered. Please help as the proffesionals have given me so many diagnosis I am getting very confused - lets hope its not all of them!!!!

 

[stuart45]

Hygroscopic salts are produced by open fires which leach into the plaster.
These attract condensation at a relatively low R/H. This is quite a common problem with old flues. Hacking off the plaster and re rendering with sand/cement/added waterproofer/salt retarder if this is the problem.

 

[asbo2010]

Thanku I did have an inkling it might be that but would it still be that if fires not been in use. I moved in a couple of yrs ago and I have not used them but have cleaned them out? any idea anyone bout the interior wall that damp?

 

[stuart45]

Thanku I did have an inkling it might be that but would it still be that if fires not been in use.

The salts would be in the plaster from earlier use.