How to repair detached ceiling plasterboard?

I noticed that my ceiling has shadow lines and when inspecting from inside my roof cavity there are areas of my ceiling that have detached from the ceiling joists where I can fit the tip of my finger in between. This detachment can be observed across 3 or 4 ceiling joists and I've noticeable this in two areas that are more open spacd. I'm just wondering if it's still possible to re-screw or whether the ceiling plasterboards need replacing?

I suspect the detachment occurred from old termite damage to the walls where the tiled roof was sitting on the homes' brick veneer back in 2014. The roof was hoisted and the walls repaired. Over time the detachment probably just got worse. The place is relatively old as it was built in 1988.

Keen to hear the community's thoughts.

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Comments

MitchellMc

Hi @nugley,

You’ll most likely be able to repair this without replacing the ceiling sheets. Use a scraper to carefully open the gap between the plasterboard and the ceiling joist, then apply some stud adhesive between the timber and the back of the plasterboard. Once that’s done, prop the ceiling back into position from below using an acro prop or a length of timber to gently push it up until it sits flush again. Then, re-screw along the ceiling joists to secure the plasterboard in place. The combination of adhesive and screws should hold it firmly.

If the ceiling joists are a bit sparse or uneven in that area, consider adding extra timber noggins between the joists to give yourself more solid fixing points. This will make for a much more secure repair.

If you can share some photos showing how far the plasterboard has dropped, that would help the community determine whether it’s still in good enough shape to re-fix or if replacement might be needed. But if it’s only sagging slightly, it should be perfectly possible to reattach it successfully.

Please let me know if you have any questions.

Mitchell

nugley

https://www.workshop.bunnings.com.au/discussion/comment/59070#Comment_59070

Here are some photos of the ceiling sag in the roof cavity as well as photos below where the sag is. It's mainly these two spots. They run across a few joists. One of them is in the middle of the dining room and the other is around the kitchen. No water stains below and paper on the back is in tact and decent condition.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/91924#Comment_91924

That's entirely repairable as per the above method @nugley. Apply some healthy dabs of stud adhesive and push it between the ceiling joist and the plasterboard. Push the sheet back up into position and then fix it with several screws to hold it in place.

Mitchell

nugley

https://www.workshop.bunnings.com.au/discussion/comment/111993#Comment_111993

Thank you Mitch. Yes, for one of the spots, I could fit a whole finger (approx. 25 mm). And looking at the ceiling below you can see shadow lines, but there's only two sheets affected by the sagging. I had a builder advise me that the whole ceiling needed replacing, but my colleagues (who are serious DIYers) thought otherwise, which is why I came on here to ask.

I tried the method you suggested along with using a damp cloth to remove dust, dirt and grime. And it looks like it's now pushed back in position. I re-screwed every 40 mm, but I might put more in so that they're spaced out every 20 mm.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/123490#Comment_123490

If you've placed a screw every 40mm, I'd say that's more than enough @nugley. I think every 150-200mm would have been sufficient. I would not add any more, as you risk cutting the sheet in half with screws, or at least, weakening it along the screw line.

Mitchell

nugley

https://www.workshop.bunnings.com.au/discussion/comment/131045#Comment_131045

Thank you Mitch. Sorry, I was meant to say every 40 cm. But I've now added more screws so that they're 20 cm apart. From the sounds of your last message, every 20 cm is sufficient. Thank you for the advice Mitch. Appreciate it.

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/135682#Comment_135682

Good Evening @nugley

A bit late to the party 🙂 But my loungeroom ceiling was as bad as yours if not a little worse, I could fit my fingers up to the first knuckle under the joists. I went a different repair route tho as the plaster would not budge and I was concerned about breaking/snapping it and then be up for a new ceiling. I didnt use a lifter tho would now 🙂 This was the first time I had worked on a ceiling.

01 22-04-2014.jpg

This end of the loungeroom ceiling joists had the "gap" I think from previous water damage but the look of it.

02 05-05-2014.jpg

If you look at the ceiling you can see how I repaired those dips you have, it was a fill and feather exercise. The dips only extended as far as you can see into the room. It wasnt too hard to do other then sanding over your head. This was in 2014 and there is still no indication that the plaster isnt level 🙂 Dodgy? mmm Nooooo It worked 🙂

03 05-05-2014.jpg

You can see the ends of the fill on the ceiling. My only note for you is to be cautious moving around in the ceiling space as you dont know what the power is terminated like.

So my suggestion is to fill and feather 🙂 How did you lift the plaster back to the trusses?

Dave

nugley

https://www.workshop.bunnings.com.au/discussion/comment/138835#Comment_138835

Thank you Dave. Appreciate your reply. I used adjustable sheet props. I was able to fit multiple fingers between the joist and board about 25mm gap in one spot. There are two joists where I didn't bud up the sheet right up to the joist but the rest I was able to bud up. Basically the old glue and screws just failed.

Thankfully I'm quite comfortable moving around in the roof cavity since I lay rat baits every 12 months and check for any roof leaks. I actually lay my snowboard across joists when I need to reach the corners and edges of the roof cavity.

Just wondering, after your fill and feather exercise did any cracks appear a couple of years later?

nugley

https://www.workshop.bunnings.com.au/discussion/comment/131045#Comment_131045

@MitchellMc @Dave-1 I have 2 spots where I glued and screwed but didn't screw the board flat against the joists. The glue has cured already, is there any way I can remove the glue and then screw the board flat to the joist?

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/135688#Comment_135688

Is there a particular reason you feel you need to fix it, such as the plasterboard visibly bulging when viewed from inside the room, @nugley? If the sheet looks flat and tidy, and you’ve already glued and screwed it, it’s not necessarily a problem that it isn’t sitting perfectly flush against the joist. There’s usually a slight gap anyway due to the thickness of the adhesive. So, unless you can see a noticeable bulge or unevenness, it’s really just an aesthetic issue rather than a structural one.

If the glue has already cured and bonded to the back of the plasterboard, trying to remove it will likely damage the sheet beyond repair. The only way to fix it properly would be to cut out that section of plasterboard, clean off the adhesive from the joist, and then patch in a new piece. If it looks fine from below, though, I’d suggest leaving it as is.

Mitchell

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/140940#Comment_140940

Good Afternoon @nugley

Lucky I am on a flexi 🙂 Tho really should be outside working on the privacy fence.

11 years 6 months ish later and still going strong.

04 10-11-2025.jpg

Only cracks I have are in the cornice above the header, most probarly from fixing the loungeroom floor that was dipping die to no studs between the beams holding the floor up above the garage.

Nice prop work, I have used something similar fixing the beams in my garage but much more heavy duty 🙂

Dave

nugley

https://www.workshop.bunnings.com.au/discussion/comment/138839#Comment_138839

Thank you for the response Mitch. I've decided to follow your advice and leave it as is. It was purely for aesthetic reasons.

nugley

https://www.workshop.bunnings.com.au/discussion/comment/142510#Comment_142510

That's held up really nicely. Thanks for showing me your works

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