Strange marks on wall

I moved into a newly build apartment in December 2001. In March 2003 (15 months after property was built \ moved into) a strange effect has appeared on certain walls. The effect looks like someone has put their fingers in grease and dabbed them sporadically over the walls. There is no pattern to this and it has only happened on the inside walls that are next to an outside wall, neither are the walls westerly facing. No mould marks have appeared and the effect does not feel damp to touch. I did have a picture frame on one of these walls and the backside of it (i.e. facing the wall) was covered in mildew. I brought the builders in to inspect it and they put it down to lack of ventilation and the moisture in the room had attracted to the walls causing this effect. They have suggested treating the wall with a ‘stain block’ product and re-painting (although they are prepared to supply painters). So the questions I have got are:
1. Is this correct what they are telling me i.e. lack of ventilation causing moisture to attract to the walls? 2. What should I use to treat the walls so that this effect will not show though when I re-paint?
Thanks,
James
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Does the house have an open plan kitchen ? Or is there a doorway through from the kitchen to another two parts of the house, e.g., one through to the hallway and one through to the living room ?
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snipped-for-privacy@earthling.net (james Mc) wrote:
Hello james

Maybe, but surely that's their pigeon if they built the thing?
It *could* be what you describe - somebody had oily or stained fingers when installing the plasterboard, and the bulk emulsion they slapped over the top won't stop it coming through.

An oil stain blocker. Used for watermarks on ceilings quite often.
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