i recently purchased a 1930s detached 2 storey house of cavity wall brick construction. The ground floor seems to be dry as a bone but we have damp staining on the first floor chimney breast at around ceiling level. It is not wet but damp/sticky to the touch.
the pointing to the chimney stack is sound as is the lead flashing. externally it looks as if the area around the stack has been re-rendered at some point historically but i am not sure why or when. Additionally, there is no sign of a leak in the eaves above the ceiling so i am at a bit of a loss.
the fire place at 1st floors level has been sealed up but there is no aur-vent/brick internally on the stack. would this be a potential cause of condensation and damp penetration?
the breast and ceiling have backing paper on them which feels damp and the paper paste is sticky to touch. upon removing the paper at ceiling height there is a lot of salting or efflorescence underneath. could this be hygroscopic chimney salting? any ideas how to eradicate permanantly if it is?