1. The plasterboard does not need to have any PVA applied – you are fine to just apply the plaster direct. However if the plasterboard is old or you are concerned for any other reason -then applying PVA will not cause any problems. Applying a small amount of plaster to test the suction is always a good idea.
Regarding this, can you skim straight onto plasterboard?
Apply a skim of plaster over each of the plasterboard joint and scim or angle beads that are on the plasterboard wall. Start in the top left hand corner of the wall and pull the plaster in from the side. If you hear the plasterers trowel scraping across the plasterboard stop! You are not applying plaster.
Subsequently, question is, how long can you leave plasterboard before skimming? Plastering on to plasterboard will dry much quicker (about 2-3 days) than on to backing plaster (about 4-6 days). As a rule plaster should be left for about a week before painting or tiling.
Moreover, does plasterboard need to be skimmed?
The stud partition walls, and often the inner faces of the outside walls too, are lined with plasterboard, but this is not skimmed with plaster. As you have discovered, plasterboard is very absorbent (so care should be taken not to get it too wet, lest it loses strength), so it has to be sealed.
Can I seal plasterboard with PVA?
PVA can be used to seal any type of porous surface,including plasterboard and if it is done properly it will give you a much much better job than working on unsealed walls. To seal a wall the PVA should be dilted at about 20 – 25% PVA to 80 – 75% water.