How to fix a sagging ceiling?

[ivanptr]

Hi,

We have a water-soaked insulation batt that caused the center of the ceiling plasterboard to sag.

We've already stopped the leak before the water managed to get through the batt and damage the ceiling board itself.

Since the sag is in the center of the plasterboard, and we're just rookies, we did some research.

It seems the first step is to use a plasterboard lifter (or T-brace) to push the board back into a flat position ? 

 

After that, we should use Zenith 8G x 50mm Gold Passivated Bugle Head Plasterboard Screws to secure the board back into the timber joists—does that sound right?

But what if there are already screws in the joist? Should we use a scraper to remove the surface layer to find and remove the old screws? 🫠

Then we’ll use self-adhesive reinforcement tape to cover the crack.

Is there a very strong tape you'd recommend for this?

[ivanptr]

@MitchellMc @EricL 

No, the joist is completely behind the cornice — it doesn’t extend beyond it at all. Today, we used a multitool to cut along the cornice joint without removing the cornice .

 

Feeling excited — making small progress today ! All the sagging sections have finally been removed. 🫠 heaps of thanks for guiding us

The blue line joist is fully occupied by the adjacent existing ceiling board, and the yellow lines are available for the new board.

1. What are the best locations to install the timber battens?

2. Which screws should we use? The joist thickness is about 3.4 cm. How many screws do we need on each side of the batten?

3. For the timber from Bunnings — what size and type should we get ?

[MitchellMc]

Hi @ivanptr,

As mentioned previously, the first step is to cut the opening back to halfway across the thickness of the roof joists. If that can't be done in some places, you would need to install batons in those areas. Currently, you have numerous edges that are not cut back to the nearest joist. Perhaps your blue line above is, but all other sides are not and are unsupported. Every edge and join needs to be supported behind with timber.

100mm long screws would be suitable, and I'd use 70 x 35mm Pine for shorter batons and any longer lengths 90 x 45mm.

I've marked in red below where you'll need batons to be placed.

Mitchell

[ivanptr]

Hi @MitchellMc ,

Could you please reupload the picture that shows where to place the battens? It looks like the image didn’t attach above.

Thank you so much.

[MitchellMc]

So sorry @ivanptr. The battens need to be placed all around the perimeter of the cutout section.

Mitchell

 

[ivanptr]

@MitchellMc 

The red line marks a joist that’s located behind the cornice, so it's not accessible to support the new plasterboard.

The yellow lines indicate the exposed joists we can use, and the white lines represent the timber battens we’re planning to install.

Does the new plasterboard need to be supported on all four edges by either a joist or a timber batten? We’re unsure how to support the bottom edge, as installing a batten there would require it to be quite long and difficult to secure.

Or if possible , could you mark where you think the timber battens should be installed?

 

 

[MitchellMc]

Hi @ivanptr,

If you take a look at the image below, you'll see how every edge of the repair sheet needs to be positioned over a joist. If you can not cut the boards back so the repair sheet is over a joist, you need to install new timbers in those positions.  
 

You've seem to have noted in white most of the required location, though there are still unsupported areas, as pointed out by the arrows below.

Mitchell

[ivanptr]

Hi @MitchellMc , today we managed to solve an issue. We used a multitool to remove the cornice on one side. The cornice remained intact, so there's probably no need to replace it

This means that side of the new plasterboard can now be secured directly to the joist without needing a timber batten — saves us some elbow grease 🫠

However when we inspected the other side with cornice , we noticed that the original plasterboard wasn’t secured to any joist at all. 

 

 

 

 

1. So we still need to install a timber batten. But there's a metal plate blocking the area, making it difficult to screw the batten in. What should we do?

 

2. If on one side the joist is too close to the brick wall, and there isn’t enough space to use a screwdriver to fix the timber batten. Is there another way? Can we use some L-shaped metal brackets? 

 

 

[JacobZ]

Hi @ivanptr,

Anywhere that you can't get in behind the truss to screw back into your timber, you can use either Dunnings 60 x 60 x 70mm M10 Galvanised Angle Brackets or Pryda Joist Hangers - To Suit 45 x 90mm to attach your timbers.

To deal with the nail plate on the truss, you can attach a piece of timber to the side of the truss that is long enough so that you can screw it into the timber on either side of the truss. You can then attach your batten as if the nail plate weren't there.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob

[ivanptr]

Hi @JacobZ @MitchellMc ,

We found that the holes on the angle bracket are too big for our screws

(Zenith 10-8 x 100mm Galvanised Countersunk Rib Head Timber Screws - 50 Pack).

What do you think about using a different-sized bracket 

A medium-sized one?

Or a smaller one?

 

We are using 70 x 35 mm timber (Framing MGP10 H2 Blue Pine), and each batten is less than 100 cm in length.

[JacobZ]

Hi @ivanptr,

Some smaller brackets would be fine as long as they have at least two screw holes on each arm of the bracket.

A pack of these Carinya 40 x 40 x 40 x 2mm Galvanised Reinforcing Angle Brackets would work well at a relatively low cost.

Just make sure you use at least 2 of the screw holes on each side of the bracket.

Let me know if you have any further questions.

Jacob