On Monday, 26 October 2020 at 14:21:25 UTC, Dave Plowman (News) wrote:
As part of a re-furb in the cloakroom - new lighting and different
plumbing, I'll have to replace the plasterboard ceiling. Approximately
1.4 x 1.2 meters. Joists along the major axis.

About half way along those, the ceiling changes to a slope - part of the
original roof design. So the joint in the pb at the bend at right angles
to the joists. And the old was cracked there - despite not being that old..

What was a sloping roof above is now a roof terrace, and IIRC the joists
for that not connected to this ceiling ones.

What would be the best way to avoid the new cracking? Suppose I could fit
noggins to support the ends. I don't intend having it skimmed, as that
would require trades brought in. (The old was skimmed but cracked anyway.)

--
*Women like silent men; they think they're listening.

Dave Plowman London SW
To e-mail, change noise into sound.
Noggins will certainly help. As you do not intend to skim, presumably you are going to use drywall filler on all the joints in that case joint tape will prevent cracking. Apply a thin coat of filler either side of the joint press the joint tape into the filler with scraper then overfill the joint and tape. Allow to set then apply final coat of filler feathering it out for at least 150mm each side of the joint.

Richard