Once the builder has lined your walls and ceilings with gibboard, you need an interior plasterer to fill in the joins of gibboard sheets and screws which are created when the gibboard is adhered to the timber frames.

What type of finish do you require?

What type of plaster is used and how many times these areas are plastered, sanded and then plastered again depends on what sort of finish you require i.e. wallpaper finish or paint finish.  A paint finish is normally done to a L4 (Level 4) finish or superior finish - this means that once the painters paint the walls the join and screw holes are not seen.  A wallpaper finish is a little more forgiving due to the thickness of wallpaper -v- paint.

What is the difference between gibboard and plasterglass ceiling sheets?

When you use gibboard you use two different products - a paper finish on top and the plaster used to fill in the joins.  When you use Plasterglass Ceiling Sheets, you get the best finish as you are dealing with plaster on plaster.