Damp seal paint or anti mould paint?

purplestar133

Hi everyone,

I have an area of painted plaster wall where the paint is crumbling off. The only thing I can think that could be causing it is condensation. It is in a cold area, next to the back door and next to the bathroom (downstairs bathroom). I try really hard to ventilate the bathroom after showers. There is an extractor fan and I always open the window, but I can't think what else it could be.

I was thinking of sanding it down and painting it with damp seal paint but I believe that paint is to stop damp coming from the inside of the wall? Whereas my problem is the damp (condensation, that is) is hitting the wall surface from the air. I heard someone talking about having mould on a wall who was recommended to use an oil based undercoat and then ronseal 6 year anti mould paint. I'm wondering if something like that would be better as, although I don't have mould, the cause of mould is similar to my problem in that wet air is hitting the surface of the wall?