Black marks on ceiling

[Shutpa]

Had an extension built 3 years ago and last year black marks appeared on the edge of the ceilings in the bedroom at the front of the house and on the shower room at the back of the house. A plasterer neighbour suggested that it was condensation and that a coat of Dulux steam and moisture paint for bathrooms would solve the problem. It hasn't. Any suggestions as to how I could sort this out once and for all? I have a feeling that perhaps the loft insulation may be at the root of the problem but it's only a feeling. Some of the spots are circular in appearance could this be the location of screws?

 

[noseall]

do you have mechanical ventilation in the bathroom?

as the problem is occurring at the peripheries of the room, and, i assume towards the outside wall, then it sounds as if condensation will be the most likely cause.
it is probably a mould growth brought about by the condensation.

 

[Shutpa]

Thanks Noseall. Yes I do have an extractor in the the shower room. But I don't have one in the south facing bedroom where I have a similar problem. Remedy?

 

[noseall]

condensation forms where moisture laden air meets a colder surface and the water trapped within that air is released as condensation. it is especially prevalent during cold winter periods.

you can combat the effects of condensation either by reducing the temperature differential through the use of insulation or by reducing the damp within the building, via ventilation or common sense.

read this too.//www.diynot.com/forums/viewtopic.php?t=76924