I have recently bought a 200 year old stone build cottage, (it is the end of a small terrace). Since the weather went colder I have noticed that around the windows on the top floor I am getting black spots of mildew / condensation stains.
The windows are less than 5 year old UPvC, and the windows on the lower floors are fine - no black spots!
Is the problem ventilation on the windows? Is it penetrating damp? Is it condensation?
I need help on this one as the missus is going MAD!!