Gavi85, good evening, and as this is your first post? hope you find a load of info in here??
Your post does not give any clues? OK there is a damp patch, but?
1/. How old is the Property?
2/. Has the external wall bee filled with Cavity fill Insulation, if so do you know when?
3/. What is the external like any chance of a Photo?
Any more info would assist in getting some ideas on what may be causing the camp patch?
Sorry if there is no easy answer, but limited info given.
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