I recently purchased a first floor maisonette, my first problem is that in the corner of 1 room (first floor) 2 damp /black mouldy patches are appearing slightly above skirting board these patches are in 2 different corners approximately 10 feet apart there are no adjacent pipes and this is an external wall with no external rainwater/soil pipes or no guttering as gable end!
My second problem is in a different room at the other end of the maisonette where again I have black mould appearing internally around the double glazed window frame!
I would very much appreciate any advice
Many thanks