Patching holes in plaster - when is a hole too big for filler?

[stuartheth]

At what point is filler no longer useful and the plaster needs a piece replaced? 

 

 

[MitchellMc]

For any hole over 10cm wide, you should consider installing a new piece of plaster @stuartheth.  You can use a reinforced plaster patch for any hole between 5-10cm. Anything under 5cm, I'd be filling. A problem arises when you try to fill a hole bigger than a 20-cent piece where your filler simply falls into the hole. You can build it up with several smaller applications waiting for them to dry in between. Alternatively, you need to find a way to back the hole and prevent the filler from falling in. There are a few ways to go about doing this. The first, if the hole is large enough, is to pack the cavity full of newspaper, and then when you can't stuff anymore in, slide in a folded piece of cardboard. Once it's inside, unfold it, so the newspaper pushes it against the back of your hole. Extra points if you remove the top paper layer and expose the rippled internal section on the cardboard; that's a great bonding surface for the plaster. The other option is to glue a couple of thin strips of timber inside the hole with Liquid Nails. I've created a rendering below to illustrate.

To answer to your question, it really comes down to how solid the repair is. You don't want a large section of wall where if the area is lent on, it caves in. The better support you can add to the inside before doing the repair, the larger the hole can be before you need to use sheeting.

Please let me know if you have any questions.

Mitchell

[RosemaryK]

5cm *6cm4cm

 HI - just tacking on to this post-  I have seen a few videos and seen the other post on this from someone else. The two holes are on your borderline I think -the bigger one is 5 *6cm and the smaller one is 4cm. I want to do this without taking the fans down or cutting up bits of wood. Would the patch kit work here on the big one? What about the smaller ones next to the fan?  Could I just use filler in those ? Could you also recommend the best filler for the jobs?    I am DIY challenged.  The fan installers just assumed I would have someone to do this for me. I don't   

[JacobZ]

Hi @RosemaryK,

Unfortunately, I would say both of these holes need a patch or backing. The smaller hole is on the borderline, but because of the proximity to the fan and the vibrations it will likely experience, it is likely to crack if it is not supported by a patch or backing.

I'd suggest using a Builders Edge 100 x 100mm Plasterboard Wall Patch for both of these holes.

You can cut one down, so it fits around the fan using a good pair of scissors. 

Once in place, you can use a plaster filler, like this Gyprock CSR 2.25kg Less Mess Multi-Purpose Joint Compound, to coat the patch. Use a joint knife or plastic scraper to apply the plaster, ensuring you give it a good mix before applying to ensure it is nice and smooth.

Do your best to apply it fairly neatly, then allow it to dry. Once dry, use a sanding sponge to sand and smooth the plaster filler, then brush it down, prime it and paint.

Nothing about this repair is particularly difficult if you take your time.

Let me know if you have any further questions or require further support.

Jacob

[RosemaryK]

Thank you Jacob!

[RosemaryK]

Hi just thought I'd show you my patching results. I used the aluminium patches with filler - sanded and then two more layers of filler with sanding in between. Then I primed and painted. I was pretty pleased with myself. Thanks for your help and encouragement . When you said it's not too hard I thought yeah I can do this!  Very satisfying - thanks Bunnings workshop people - always helpful. 

PS Yes I will get rid of that bit of masking tape at the base of the light fitting.

 

[JacobZ]

Hi @RosemaryK,

You've done an absolutely amazing job; you can't even tell that it's been patched.

Congratulations on learning a new skill that you will now have for the rest of your life. You should be proud of what you've achieved.

Jacob