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How to fill corner gap?

Hey all, wondering the best way to fill this gap.

It's in the corner of the wall near the front of our house. It's been like this for 8+ years, so pretty confident it's no longer moving, we've just been lazy about fixing it.

The wall on the other side appears fine.
I was wondering if the move is to just to remove the old loose material, fill it up with sellys no gap, sand it back, and paint over it? Or is there a better technique for this job?

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MitchellMc

Hi @Jarrod1,

The first step would definitely be to clean out all the loose or crumbly material that has delaminated from the corner, so you are working back to something solid. From the photo and your description, it does look like a reasonably large gap, which suggests there was some significant movement at some point in the past.

If you are confident there is no longer any movement, you can fill the gap using a sandable gap filler, allow it to cure, sand it back flush and then repaint the area. That will give you the cleanest visual finish. If, however, there is any chance the corner could still experience minor movement, even seasonal, a paintable silicone or flexible gap filler would be the safer option as it will tolerate a bit of flex without cracking.

Because the gap appears fairly wide, you will almost certainly need to use a backing rod, around 6 mm is typical. Push this into the gap just below the surface so the filler or silicone has something to sit against rather than disappearing into the wall cavity. Once filled, if you are using a paintable silicone, smooth it off with a wet finger to form a neat, consistent line between the two walls before painting.

Either approach can work well; it really comes down to whether you want a rigid repair or one that allows a little ongoing movement.

Please let me know if you have any questions.

Mitchell

Jarrod1

I've cleaned out the loose parts, and yeah the gap is quite big now, around 1cm.

There seems to be a void behind it, so not sure I'll be able to get the backing rod to stay in place, are there any alternatives?

Based on the cleanup, it seems like there was existing paper in the corner, not sure what product is best for going that way, or some sort of metal angle plaster trim instead?

JacobZ

Hi @Jarrod1,

The backing rod should be a little bit wider than the gap and compressed between the two surfaces when it is pushed into the void. It should still work, but there is a risk that it could be pushed through the void quite easily after applying your sealant over the top, so you might like to consider using another method.

Considering you found paper, which is almost certainly paper tape used in a plaster jointing system, and it has failed, likely due to the size of the opening, my suggestion would be to use a rigid metal plaster trim such as this Siniat 30 x 2400mm 90° Internal Angle Plaster Trim.

They can be fixed in place with staples, then overcoated with a coat of base coat followed by a coat of topping compound. The process is much the same as the one shown in How To Attach And Plaster An External Angle, except you are using an internal angle.

If you have further questions about the process, please let me know so I can assist further.

Jacob

Jarrod1

Thanks Jacob, just want to confirm I'm getting this straight.

With the area clean, I would stick this into the corner https://www.bunnings.com.au/siniat-30-x-2400mm-90-internal-angle-plaster-trim_p0730709

I nail it into position with plasterboard nails https://www.bunnings.com.au/paslode-30-x-2-8mm-500g-plasterboard-nails-250-pack_p2360595

I go over it with this, giving it a couple of coats https://www.bunnings.com.au/gyprock-csr-2-25kg-less-mess-topping-compound_p0173348

Then prime/paint it.

Or am I missing something? I don't really understand what is meant by base coat / top coat, is that just the same plaster material but 2 coats?

MitchellMc

Hi @Jarrod1,

That's correct.

Jacob has linked both the base coat and the topping compound. The base coat is used for the bulk of the filling over the angle, which you'd then sand down flat. The topping compound is the top layer, which is a finer particle and designed to get a better finish. You'll skim coat this over the previous basecoat layer and then sand to a smooth surface. Then you can prime and paint.

Mitchell

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