Cracks in ceiling plasterboard

[jesteh]

I am trying unsuccessfully to fix cracks in plasterboard ceiling with following problem. Plasterboard has been fitted on a vaulted ceiling around Velux windows. The plasterboard is 12.5mm and the joints are unfortunately at the corners of the window making it a weak point. As a result, plaster cracks from corner of the window straight up and down the ceiling.

As a first attempt, I raked out and re-filled the cracks. They re-appeared after couple of days.
Next attempt - I raked out the cracks, sanded down the plaster around them and re-filled with toupret elafib and taped with toupret scrim again bedded in elafib. I then covered the whole lot when dry with surface filler and repainted - this time cracks re-appeared after a week.

So really - I am at a point of giving up unless there is another solution?

 

[PrenticeBoyofDerry]

It would only be a weak point, if there was nothing secure to fit the boards to?
Have a picture of your problem?

 

[jesteh]

Just looked at it again and the flexible filer did not crack - what cracked instead was the surface filler applied over the top of it (Toupret Cachet Bleu).

Once I sanded back the surface filler, no crack showing through the flexible stuff. Not sure if that means I applied filler on too thick or something else? What am I doing wrong?

 

[PrenticeBoyofDerry]

not sure, not product i use, so do not know how it behaves!
I prefer easifill

 

[roughcaster]

Instead of putting on one single length of scrim tape along the plasterboard crack/s, I put on a lot of small 3 or 4 inch pieces of tape, "across the whole length of the crack ".
It takes a little longer and you use a bit more tape, but it's far stronger because each single piece of tape is a separate barrier. Once the tape is on, go over it with a couple of thin coats of ready-mix, feather it out, then sand it down when dry with a 150 grit sandpaper. I do it that way all the time and it works a treat, even on minor cracks in lath and plaster. Try it and see.
Be sure to check too, that there's no movement in the plasterboard, and if necessary, put in a few extra screws before you attempt any repair.