I'm living in a new build (A rated) for just over 4 years. I've noticed for maybe the last year that damp patches have formed on the outer wall in the ensuite. All other rooms are fine.
The first ones to appear were the two directly above the window, on flat horizontal part of the window 'cutout' (nto sure the proper name for this). These are exactly symmetrical with each other which is unusual.
Then more recently (some time after the summer) additional ones started appearing on the wall above the window, as well as an additional one right next to the extractor.
The outer wall has insulated plasterboard on the inside of the block.
The damp is worse after I have a shower in there.
I'm not sure if it's a ventilation issue as the extractor comes on with the light (I always ensure it is on regardless of whether I need the light on or not). Also the extractor itself provides ventilation even when off.
I usually have the window open during the day, until it's really cold out.
Any thoughts on the cause of these damp patches, and whether some damage might already be done inside the wall? I don't work in the building trade so don't really have a clue about this.