I always thought that before you skim coat a wall/ceiling of plasterboard, you need to put skrim over the edges/gaps in the board and pop some filler in the gaps. Its normal straight edge board btw. I've just seen a plastering video, and the chap on there was skimming over the skrim, with no filler in the gaps.
Is this normal? Is the filler only necessary if there are large gaps between the boards?
Thanks in advance
James