On Sep 1, 7:21*pm, Andy Dingley wrote:
Damp patch inboard *of an outside chimney, with no obvious cause or
broken thing to fix.

Late-Victorian three storey, with an external brick chimney for the
old kitchen range.http://quercus.livejournal.com/24010...43408#t1343408
The chimney is capped at the top (paving slab), but unventilated at
the bottom. It has a lead gutter into the corner of the roof. *Access
is a pain, as I don't have ladders to do it and there's also a
protruding conservatory beneath.http://quercus.livejournal.com/324272.html

Had a laddery chap up there a while ago to tidy the other chimney
stack, and he reported no obvious cause.

Inside has been damp for some years, to the point of peeling paper and
the plaster starting to fail. As there's nothing visible outside, and
I plan to insulate inside anyway, I've now started hacking the plaster
off inside. I hope to find an obvious damp spot, otherwise to tunnel
out onto the roof from the insides (at least with an endoscope).
Pulling the plaster showed at least three vintages of plaster on
there, so I think it's an old problem with some partial repairs done
in the past.

Now I've found thishttp://quercus.livejournal.com/324272.html?thread=1343408#t1343408
This is staring at the inside wall of the chimney, from the turn of
the staircase onto the top floor. *There appear to be two holes into
the chimney from inside, as if they were flues(?), blocked off by
bricks placed into them afterwards. *Beneath the lower one, there's
also a horizontal length of timber set into the brickwork beneath the
plaster. Support for the staircase? It's a bit low to be a plate
supporting the floor joists.

Why would my kitchen range chimney have "flue holes" in it two floors
above? *Was this common? *Some temporary construction measure?

Any thoughts on de-dampening would be welcome!

If that chimney is out of use, I'd consider removing it and slating
over the hole.
It will always be a problem and always need maintenance. It could even
fall on a windy day at some time.

The cap is too small and the lead flashing has not been properly
installed.

You could consider some flashband as a temporary measure to fix both
problems.