On Monday, 26 October 2020 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.)


Scrim over the joint. Retrofit on existing plaster by grinding away the plaster on either side of the joint, Apply the scrim with Polyfilla of similar.
https://www.randjbuildershardware.co...astering-tool/