In article . com,
"Staffbull" writes:
Can you let me know which way the plastervoards should run, with the

Usually across.

trusses or against them (long edge of the board) and which way up,
smooth paper side or rough.

You plaster or decorate the ivory side.
You may find references saying decorate ivory side or plaster grey
side, but this was for plasterboard 20 years ago, and doesn't
apply anymore. In practice, it makes little difference for plastering.

I think they should run with the truss timber, and my brother thinks
they should run against, i think they should go smoothside down
(plaster face) and he thinks rough.

A also think the short ends of the boards will be OK butted together
unsupported as the centres are only 360mm.

This can work if all your ceiling joists are level, otherwise you
end up with steps. I might not do it with 9mm plasterboard though.
Leave a 1/4" gap between unsupported edges, and start the plastering
by forcing bonding coat plaster through the gap and right through to
the back, with an excess overflowing onto the board tops. This will
bond the board edges together so they can't move relative to each
other. Apply scrim tape (nylon course netting) to the joins before
you put the finish coat on.

If you are not doing the plastering yourself, ask the plasterer if
he wants the 1/4" gap at floating edges -- some do, some don't.

--
Andrew Gabriel