HI, Just decorating a house from the late 70’s early 80’s build and the painted over wallpaper has separated at the joins, it looks like it’s gone back to the plasterboard, can I just seal it with unibond pva clear adhesive and the paint and wall paper or should I get the plasterboard replastered?
If the paper is firmly stuck then you’ll need to fill the joints level with polyfilla and rub down so the joint is not obvious. However, you may find the water content in the filler will cause the joints to swell, thus causing more problems. The same would be true with your PVA suggestion.
The best way to avoid this is to seal the joints with an oil-base paint first. It doesn’t really matter what kind of paint you use, any undercoat or general purpose primer will do so long as it is oil-based.
Give it 24 hours to fully cure before applying the filler and that should do the trick. When you have smoothed down the filler you’ll need to seal this in order to get a uniform base on which to redecorate.
You can use a thin coat of water-based paint to achieve this. You should then be able to redecorate without the previous open joints become visible.