Another member mentioned that its ' It's only cold spots coming through on the dot & dab. It's no worry. You only need to paint over with a little help from the supplier. Just tell them what's happened & they will give you the correct paint to use... '
If the house has been unoccupied for some time without heating etc, it's probably made it more noticeable. Painting over it with a stain blocking or oil based paint may cover it for a while, but ultimately you're hiding a potential damp issue.
Dot and Dab is used to cover masonry on virtually every single new build and extension I've seen in the past twelve years. It works. It works well. If there was a common problem with oils in the adhesive leeching through the plasterboard leaving visible damage on the interior, then dot and dab would never be used. Or the adhesive would have been changed. Imagine you work for Soudal, and your R&D guy comes and says "We've made this great new product. It sticks plasterboard to masonry. Its strong, quick, cheap to make and has a long shelf life" " Thats brilliant Alan, just what we need. So no issues at all?" " No none. Except after a year the oils in the glue work through and spoil the paint in Mrs Jones nice new house decor and we'll get sued by the housebuilder" " Ok Alan, don't let the door hit you in the **** on the way out" If it is condensation on cold spots, then the wrong adhesive has been used, and problem wont go away. If it is moisture working through from the outside, it won't go away. If it is oils in the adhesive, then the plasterboard is contaminated, and it won't go away. Get a quote to get the wall re-done with insulated plasterboard. probably cost less than a grand and make for a better, warmer room.
As you’ve not bought the house yet, factor in a couple of thousand for redoing the wall into your offer, before you hack it off I would paint it with a Zinsser product (123 perhaps? Astramax would be the man to confirm which one) to see if it tempers or solves the spots, if not you’ve only lost a few quid so then remove it and fit new insulated boards.
Zinsser i have read about would this help ? Also gutters have been cleaned in the house and no leaks.
First thing is to check that the dot and dab marks are dry before any stain block is applied, if it is proven to be 100% dry paint over with paint the whole wall with Zinsser Bullseye 123 or Zinsser Cover Stain.
I hope so otherwise I’ve suggested the wrong product, however as I said, if it doesn’t you’ve lost very little and will be removing the plasterboard anyway.
Yes....only if the wall is dry, personally I would prefer the Cover Stain if it were to used to seal over a previously damp area which has now dried.