Damp patch on upstairs fireplace

[Lucyadela]

Hoping someone can help....

My bathroom has a bricked up fireplace (no air brick) recently we completed some work in the kitchen below and had to support it from below as this had not been done properly by the previous owners. Since this work a small damp
Patch has appeared on the upstairs fireplace wall which I can get rid of.

I'm not sure if it's something to do with the support underneath, the fact there is no air brick or something chimney / flashing related....or something else?

I've attached a few photos

 

[Lucyadela]

Link to picture:
//www.diynot.com/network/Lucyadela/albums/

 

[Burnerman]

Lovely bathroom, but can you be more specific as to where the damp is?
Anyway, a dead chimney really needs to be ventilated, and a pic of the outside would be good!
John

 

[foxhole]

Chimney needs a vent as stated.