Fitting sheetrock(plasterboard) to a ceiling, to be taped and skimmed. Should the joints be tightly butted, or leave a gap, of what size?
Tight.  Sheetrock doesn't &quot;move&quot; like wood does. Fit it as tight as you can, but don't go overboard on the labor.   I've seen some pretty sloppy jobs of hanging rock that got muudded and taped and turned out OK. Problem is sometimes if the gaps are too large, the mud eventually shrinks  and they open up and you get some cracks.   Best practice is as tight and clean as possible when hanging rock.