Hi, I realise that this might be a duplicated question but....
I live in a converted victorian building and have just noticed dampness in my bedroom and lounge on the exterior walls. It is a kind of greeny/black, very fine "fur" for want of a better word. I am presuming this is a type of damp however it does not appear to me to be penetrating from the outside wall. Is it possible that it is a result of my bathroom and shower? I must admit I rarely close my door when having a shower.
Thanks