Thin plasterboard - need help with hole!

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malamute5

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#289142 15-Aug-2021 18:31

Hi all,

I am by no means the handiest of men when it comes to DIY but we have not long purchased a house and while having it rewired the electrician had to remove the old and apparently dangerous electric central heating system.

This has however left a rather large hole in the wall in the hallway which I would like to patch up. It seems too large (about 300mm X 150mm) for the patches you can buy from the hardware store however the wall is only 80mm thick so am I correct in thinking that I couldn't get some gib board that doesn't seem to come thinner than 100mm and just stick it in the hole?

If anyone could suggest the best way to patch this up that would be great. Otherwise, I guess I might have to bite the bullet and get someone more capable in!!

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#2760319 15-Aug-2021 18:48

As a DIY'er (not a builder), my concern with a hole that size would be that a patch placed on top would be weak. The way I'd do it would be to cut a patch from something like another piece of gib or hardboard, drill a couple of small holes in it near the centre for running some string through. Then I'd run glue around the outside of one face. After that it'd be a matter of feeding the patch into the hole and pulling the glued face hard up against the inside of the wall using the string and holding it there for a few minutes. Later the string can be cut and pulled out and another piece of gib glued onto the hardboard. After some curing time the gaps between the existing gib and the newly installed 'patch' can be filled with the filler of your choice.

malamute5

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#2760322 15-Aug-2021 19:07

Thanks for that. The only issue with that is the wall is only 80mm thick and I can't seem to find any plasterboard that is the same, it seems to be a minimum of 100mm 🤷‍♂️

RunningMan

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#2760324 15-Aug-2021 19:14

Gib will be either 10mm or 13mm, never 80mm or 100mm. Can you post a photo?

mattwnz

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#2760325 15-Aug-2021 19:20

RunningMan:

Gib will be either 10mm or 13mm, never 80mm or 100mm. Can you post a photo?

I think some of the older gib was thinner. Pre 2002ish I know this because of a problem a builder had patching a mistake made in a bathroom. Builders are used to patching gib during builds so this sized patch shouldn't be that much of a problem.

malamute5

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#2760329 15-Aug-2021 19:25

The house was built in the '50s.

I stand corrected, I meant to say 8mm not 80mm!

Dratsab

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#2760331 15-Aug-2021 19:31

Looking at that, and given it's only 8mm, I'd put in a rear mounted patch I suggested above and simply fill it with a gib stopper. Not all in one go though as it'll shrink and crack as it dries - a couple of layers. After sanding smooth you'll only be left with the problem of disguising it :-)

People who actually know what they're doing may well have better suggestions though.

RunningMan

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#2760332 15-Aug-2021 19:37

malamute5:[snip] I stand corrected, I meant to say 8mm not 80mm!

OK, that makes a lot more sense. Rather than buying a patch sheet which will be uniform thickness (10mm) everywhere, you need to cut your patch from the edge of a full sheet. The first 60 (ish) mm of a sheet is thinner (tapered) to account for tape and plaster to cover the sheet joins. No point in buying a whole sheet - you just need to find someone who has offcuts that include a tapered edge.

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eracode

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#2760354 15-Aug-2021 21:29

This site shows the way I have done this in the past - refer to the ‘large holes’ solution. If your gib is only 8 mm thick (which seems quite strange), and your patch piece is standard 10 mm, reduce the thickness of the gib patch piece by removing the backing cardboard and about 3mm of the gypsum from the back of the patch. Then glue the patch in and skim plaster it to bring it into line with the wall face. Then sand and paint.

https://www.lowes.com/n/how-to/patch-and-repair-drywall

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larknz

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#2760357 15-Aug-2021 21:43

The wallpaper around the hole is going to make it very difficult to disguise the patch.

eracode

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#2760358 15-Aug-2021 21:47

larknz: The wallpaper around the hole is going to make it very difficult to disguise the patch.

Looks like it may be scrim rather than wallpaper. However scrim was usually nailed onto wooden sarking, not on to plasterboard, then wallpaper was stuck to the scrim.

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mattwnz

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#2760365 15-Aug-2021 22:43

eracode:
This site shows the way I have done this in the past - refer to the ‘large holes’ solution. If your gib is only 8 mm thick (which seems quite strange), and your patch piece is standard 10 mm, reduce the thickness of the gib patch piece by removing the backing cardboard and about 3mm of the gypsum from the back of the patch. Then glue the patch in and skim plaster it to bring it into line with the wall face. Then sand and paint.

https://www.lowes.com/n/how-to/patch-and-repair-drywall

Older gib seems to be about 9.5mm as shown at https://www.renovate.org.nz/1940-60s/interior-features-and-finishes/internal-wall-and-ceiling-linings-original-details/

Bung

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#2760366 15-Aug-2021 22:58

I have memories of similar wallpaper. The wall lining is fibrous plaster rather than Gib. It wasn't wrapped in paper so it was thinner.
It shouldn't be too difficult to set the support for a gib patch back so the front of the gib is flush. Alternatively there is a "California patch" method where the patch starts oversized and the edges are trimmed to fit the hole leaving the front paper overlapping.

neb

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#2760370 15-Aug-2021 23:35

To get a bit that tiny, go to your local M10/Bunnings and see if you can grab a scrap from somewhere, they often have scraps lying around which means you wouldn't have to buy an entire board. Then glue some scrap strips behind the existing gib so they cross over the opening and glue the scrap gib in place. Finally, patch the edges with any kind of filler.

The killer is going to be finding matching sackcloth to glue over the top of it...

tdgeek

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#2760377 16-Aug-2021 07:29

neb: The killer is going to be finding matching sackcloth to glue over the top of it...

I'd put a picture over it. If its low, or high, a fake vent.

chevrolux

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#2760389 16-Aug-2021 08:40

I'd be less worried about the plaster, than about fixing whatever that wallpaper is.

That hole isn't that big, I'd just pull up something on the back of the hole (like another piece of GIB), and gradually fill up the front with compound.

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