damp at bottom of chimney breast

[boulderburns]

I started stripping a ground floor room for redecoration, and found damp, flaking plaster at the bottom of a bricked-up chimney breast. The breast is in the centre of a shared internal wall and has a vent at approx 18 inches up from the floor. I have opened the vent and cleaned all of the accumulated guff from inside the chimney (there wasn't very much of this) but the breast hasn't dried out yet (a few months later). There appears to be no damp anywhere else anywhere in the room, nor anywhere else in the house for that matter, and on this breast the damp is confined to the bottom 12 - 18 inches, and mainly at the side of the breast. Am I right to suspect that improving ventilation may cure this? Can I safely put airbricks in the sides of the breast? Any ideas would help. Cheers in anticipation..

 

[Zampa]

The chimney lining may have goen....id get that checked too

 

[TexMex]

This kind of problem is quite often caused by the lack of a DPM in the fireplace. Although the brickwork includes an adequate DPC, the fireplace in front of it, is often set onto some concrete and loosefill, laid directly onto the oversite, with no DPM. Damp then rises up through this and across onto the brickwork of the Chimney, above DPC level.

This was another of those foibles our venerated old craftsmen were quite happy to install. Try lifting some floor boards around the fireplace and check for signs of damp there.

 

[boulderburns]

Thanks for the ideas ,peeps.
Problem is that there are no floorboards to lift, it being a concrete floor (soz, forgot to mention that). As you can imagine, digging holes around the chimney is going to cause more upheaval than the problem possibly warrants, there only being small areas of damp. (Or am I just fighting shy of opening a can of worms?) As you may have guessed I'd like to get away with as little collateral damage as possible, so I was really wondering whether;
A) at 18" off the floor, the existing vent is too high, and therefore shifting it down the face of the chimney breast by 12" say,may improve airflow where it is needed, or
B)installing extra vents, ie. air bricks on either side of the chimney breast at low level may do similar, or
C) a cunning combination of A) and B)
It may or may not be worth mentioning that there appears to be no hellish, major dampness problem, and none at all above 18".