Hi All, I'm about to embark on a project to pull down my existing lath and plaster ceiling and replace with plasterboard, prior to having it professionally skimmed. I plan to use 12.5mm square edged boards, and would be grateful if anyone could advise on the following: 1) Should the boards be laid with the long edge across, or along the joists? 2) Do all edges need supporting? (i.e - will I have to fix noggins between the joists along each unsupported edge?) 3) I've received conflicting info about what length of screw to use - some people have suggested 38mm, some have said not to use anything shorter than 50mm - who's correct? Thanks for any advice! Dave.