best way to joint fill gaps

[Snowbound]

Before I get my ceiling plastered I need to tape and fill but there is one joint that is about 10mm wide and one that is about 15mm. Is it still OK to tape and fill as normal or will I need to do something different??

 

[PrenticeBoyofDerry]

I'd fill the gap first with filler, let that set then sand as it may belly, then apply your tape/scrim.

 

[Richard C]

If I’ve understood correctly, you’re going to plaster it They are very large gaps to have in ceiling boards, how long are they & how did you end up with them? Is there any support (joist) behind the gap? You must fill the gaps before taping & plastering or you will see it & it will certainly crack.

I normally use Bonding plaster to fill gaps & then stick 3 overlapping layers of reinforcing tape over it before plastering but 15mm is one huge gap to leave unsupported in a ceiling & I wouldn’t be confident it won’t crack. One solution may be to cut a strip of plasterboard & stick it in there first using wallboard adhesive if you have any or a decent grab adhesive will do it; fill the smaller gaps with Bonding, tape & skim as before.

 

[NickB_99]

One solution may be to cut a strip of plasterboard & stick it in there first using wallboard adhesive if you have any or a decent grab adhesive will do it; fill the smaller gaps with Bonding, tape & skim as before.

Rich C - Before I read the solution, I would have gone with the p/board strips as you suggest, but filled around the strips and other small gaps with wallboard adhesive.
Not contradicting - but is there a reason why you wouldn't use wallboard adhesive, and prefer Bonding for this?

 

[Richard C]

Rich C - Before I read the solution, I would have gone with the p/board strips as you suggest, but filled around the strips and other small gaps with wallboard adhesive.
Not contradicting - but is there a reason why you wouldn't use wallboard adhesive, and prefer Bonding for this?

Both Wallboard & Grab adhesive will shrink back on curing, Bonding plaster doesn’t. So stick it in there with adhesive, fill it out with Bonding; no shrinkage = flat surface to tape & skim.

 

[renia]

The planes don't line up flush but I prefer not to cover and realign them. So can I fill the joints with compound then tape, then paint? The joints have been painted, wallpapered, and repainted with resulting bubbles and cracks in the paint. It's a 1910 farmhouse. Thanks!