Do you mind looking at the chimney pic at the bottom of this page
of this site
My chimney in the back reception is like that. It backs onto another chimney in the kitchen (were they called boiler chimneys??)
Anyway the brickwork between A and C in the diagram is crumbling. In fact, it's so powdery that I can easily shove a screwdriver into each brick. This is from the hearth up to a height of about 18 inches
That is almost certainly caused by damp, but whether it's damp coming up from the bottom, or rain coming down the chimney I'm not sure. But I'll look at that as a separate issue.
What I'd value advice on is whether or not the bricks in that part of the diagram are supporting or not. Just how far can I go with digging out these crumbling bricks before I am in danger of the whole wall coming down?
Thanks in advance - and apolgies if its the wrong forum