Grunff wrote:
Chris Bacon wrote:
Squirt in some 3:1 PVA, don't rake out the cracks first.

Or just fill with some flexible decorator's filler...

Ahbut, sticking it together does a far better job, if the crack is
"fine", say 1/2 mm, caulk won't take up the movement. The PVA treatment
is also excellent for plaster & lathe ceilings, as it glues up any sandy
stuff which would otherwise fall from above, bulging any paper and
displacing filler... try it!