Chimney Problems or just an old stain showing up?

[ergr]

Hi,

This is my first post so hope it makes sense and people might be able to help.

I moved in to my 'cottage' flat (1st floor - I have the roof space!) and everything seemed great. About a 6-9 months after moving in I noticed a yellow stain on my living room ceiling. There used to be a fireplace (internal wall) close to where the stain is but it was removed before I bought the flat. The chimney stack has been removed to below roof level and the roof re-tiled etc. At the open top of the stack there is a vent in the roof space which I assume would help with ventilation. The previous owner had this work completed and also put other vents in the roof space. Apparently the chimney was leaking (and causing damp) and so was dealt with.

Should I worry about my yellow stain?
The ceiling has been wallpapered and at places in this stain it has bubbled away from the ceiling. Yesterday I touched a bubble (out of curiosity) and it just flaked away.

I went to the loft and pulled back the insulation and it does seem slightly wet or at least there has been some moisture present but I cannot see how it got there.
I have also pulled away some more paint and took a tiny circular part of the bubble down to the plasterboard.
//media.diynot.com/193000_192505_49736_99886081_thumb.jpg

I'm concerned that I have a big problem here. Any advice would be great.

 

[Blagard]

I would suspect a leak. The source is not always obvious. Try to eliminate things like water pipes (can even be condensation on a pipe that does not leak), leaking tanks etc. The roof is always on the suspect list, so try checking out the loft when it has been raining heavily. Roof leaks may manifest themselves some way from the actual source of the problem because water can run down felt , rafters and even from lower places when in exposed situations due to wind driven leaks.

If you can spot the "leak" in action it helps no end when otherwise the source is not obvious.