Ceiling hairline cracks

[hr21]

Hi all, I've got an old ceiling which seems to have been reskimmed at some point. Not a good finish at all so I am looking at a textured paint at some point (unless there are better options?)

However, we had some French doors fitted and there was a hairline crack running across the entire room. I was going to repaint the ceiling and decided to scrape back the cracks with a Stanley knife, fill (with red devil filler), paint with mist coat and then with paint itself (dulux matt white)

Hairline crack has come back (though far less than before) seemingly through the filler.

I am wondering what I should do next in order to get ceiling sorted?

There is a partial issue with the floor (seems to flex a tad, though not a structural issue) which can of course lead to these cracks reappearing.

Any thoughts or opinions on this?
Thanks

 

[sparkwright]

Have you access above?

If so, fit wooden noggins on the top of the ceiling over the length of the crack.

And then fit screws into the ceiling either side of the crack into the noggins.

 

[sparkwright]

Easi-fill may help you to improve the finish of the whole ceiling, where it was badly re-skimmed.

 

[hr21]

Easi-fill may help you to improve the finish of the whole ceiling, where it was badly re-skimmed.

Thanks,
yes I think noggins would be useful across the centre, what wood would you advise to use here?

Easi fill gyproc? Which one, 20, 60?

 

[sparkwright]

Nearly any kind of soft wood would do. 2" wood perhaps, depends on what available space there is.

Best to fit the noggins to nearby joists (before screwing through the ceiling) to ensure nothing can move.