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Advice For Filling Holes In Plasterboard

Posted: Mon Sep 16, 2019 3:27 pm
by mrsparks
I've had a few holes to repair in our plasterboard walls recently and when I've painted them over I've never been happy with the finish. The walls are dot and dab and pretty sure they're lined with lining paper and emulsioned. So, for example, I needed to remove some old rawplugs. Dug part of them out with a stanley knife, filled with polyfilla, sanded and painted over with a roller. I'd swear that I've sanded to the point where the surface is flush but when I roller over them you can always tell that they've been filled. They surface is slightly proud, I suppose - a slight dome shape. What am I doing wrong?

Advice For Filling Holes In Plasterboard

Posted: Mon Sep 16, 2019 4:04 pm
by wine~o
pics of the offending areas might help. Could just be the paint flashing

Advice For Filling Holes In Plasterboard

Posted: Mon Sep 16, 2019 4:47 pm
by mrsparks
wine~o wrote:
Mon Sep 16, 2019 4:04 pm
pics of the offending areas might help. Could just be the paint flashing
Will do. Need some natural light though.

Advice For Filling Holes In Plasterboard

Posted: Mon Sep 16, 2019 5:43 pm
by mrsparks
Light was OK, as it turned out. Example attached.
Poorly Polyfilled Hole.jpg
Poorly Polyfilled Hole.jpg (158.92 KiB) Viewed 326 times

Advice For Filling Holes In Plasterboard

Posted: Mon Sep 16, 2019 7:51 pm
by OchAye
Before I saw the photos I thought I knew the problem, but having seen the photos you are correct in your description. My only "guess" is that the filler is cr@p, once you paint over it it expands by absorbing juice from the paint (too much gypsum too little else that might have kept it more stable). I am only saying that because I am a Toupret fanboy.

Advice For Filling Holes In Plasterboard

Posted: Mon Sep 16, 2019 8:22 pm
by mrsparks
OchAye wrote:
Mon Sep 16, 2019 7:51 pm
Before I saw the photos I thought I knew the problem, but having seen the photos you are correct in your description. My only "guess" is that the filler is cr@p, once you paint over it it expands by absorbing juice from the paint (too much gypsum too little else that might have kept it more stable). I am only saying that because I am a Toupret fanboy.
Interesting theory - and it would absolve me of all blame! Honestly, when I ran my hand over it after sanding it felt perfectly smooth. I tend to use ready made Polyfilla in a tube, which is quite old (very old actually) so maybe I need to try something different and newer. I've used Toupret Acrylic Filler in a cartridge for caulking but it would be a bit fibrous for holes like this I think but I presume they do an equivalent to Polyfilla powder. The other thing I notice when applying from this tube is that it is difficult to spread and get a tidy finish with a filling knife - it's like the moisture gets sucked out of it immediately and starts to go crumbly. At that point I stop because playing with it further just makes more mess.

I hate the dot and dab walls. Apart from the problem of getting the right plugs when hanging something heavy, filling and sanding is a nightmare. There's a previous layer of paint, lining paper, then the paper lining on the plasterboard and it's hit or miss whether you're in a dot. My previous house had proper plastered solid walls, so was much easier to deal with. At least you could sand without fear of doing any real damage.

Advice For Filling Holes In Plasterboard

Posted: Tue Sep 17, 2019 2:16 pm
by mrsparks
Thinking about this further, I guess I've come to the conclusion that (apart from using a different filler) when I'm repairing, say a rawlplug hole in my dot and dab, paper lined and emulsioned walls, there's no point filling slightly proud and sanding back. And especially avoid filling beyond the actual hole itself, because sanding down an area that's going to have, from out to in, filler (albeit not much), previous emulsion with a textured finish from rollering, lining paper, and then plasterboard, is not easy. Clearly you need to avoid sanding beyond the lining paper but if you don't go far enough you're not going to have a finish that blends in.

Advice For Filling Holes In Plasterboard

Posted: Tue Sep 17, 2019 4:35 pm
by wine~o
Don't "dig" the old rawlplug out, drill it out. then fill ... I find a powdered filler better than premixed. Fill slightly proud then with a wetted filling knife swipe over the filled area to smooth.

Advice For Filling Holes In Plasterboard

Posted: Tue Sep 17, 2019 7:48 pm
by OchAye
Like Wine~o I am with powder fillers. Bog standard toupret, 2Kg between £7-8. The thing with filling any hole on a painted surface that has orange peel is that you introduce a flat surface. You can sand a bit around it but still it is difficult to hide (and no, do not sand through to the lining paper). The only way I have is to go over the patch with a mini roller gadget with the same pile as what I use anyway, and then revisit a few times whilst the first coat is still wet. Or in other words, I am trying my best to create orange peel which I can do any time when I do not want it.

PS. There had been another thread with some guy filling cracks and once he painted the filler became proud ...
PPS. All gypsum based products have a shelf life, ready mixed even more so, and once opened ... a few weeks at best.

Advice For Filling Holes In Plasterboard

Posted: Tue Sep 17, 2019 8:03 pm
by mrsparks
wine~o wrote:
Tue Sep 17, 2019 4:35 pm
Don't "dig" the old rawlplug out, drill it out. then fill ... I find a powdered filler better than premixed. Fill slightly proud then with a wetted filling knife swipe over the filled area to smooth.
Thanks but not quite sure I understand how to drill it out? Do you mean by using an oversized bit?

When filling slightly proud, would you overlap the edge of the hole? I'm guessing one of my mistakes is spreading the filler too far I'm afraid of sanding to vigorously in case i damage the underlying lining paper.

Now I need another hole to practice on. Actually, I've got a whole bunch of them on a wall adjacent to our bathroom. When we had the bathroom refitted, the lad who removed the existing tiles was so aggressive that he popped a load of plasterboard nails on the other side of the wall - in a bedroom. I've filled some and sanded down but in a certain light I can see that they are showing the same problem as the example I posted in the photo.

Sorry @OchAye, I'd composed this before you posted.

Advice For Filling Holes In Plasterboard

Posted: Tue Sep 17, 2019 8:13 pm
by mrsparks
OchAye wrote:
Tue Sep 17, 2019 7:48 pm
PS. There had been another thread with some guy filling cracks and once he painted the filler became proud ...
PPS. All gypsum based products have a shelf life, ready mixed even more so, and once opened ... a few weeks at best.
The tube of ready mixed Polyfilla I have is years old. I'll be looking at Toupret filler in future. Problem is, of course, when your average DIYer only does a job once in a while it's impossible to buy a small enough quantity just for that job, so you either end up throwing the remainder away or keeping it for years until it eventually runs out, or goes off.

Advice For Filling Holes In Plasterboard

Posted: Tue Sep 17, 2019 8:29 pm
by OchAye
mrsparks wrote:
Tue Sep 17, 2019 8:13 pm
The tube of ready mixed Polyfilla I have is years old. I'll be looking at Toupret filler in future. Problem is, of course, when your average DIYer only does a job once in a while it's impossible to buy a small enough quantity just for that job, so you either end up throwing the remainder away or keeping it for years until it eventually runs out, or goes off.
I know! I am a diyer too. By the time I get off my posterior to do something, and pay e.g. for Crown Trade Paint prices not B&Poo 15lt for £20, using some filler knowing the rest will be wasted is a choice I make. You can't get toupret powder in less than 2Kg, so it is best to decorate more than one room at a time :-)

I will let wine~o explain his method but on holes I do not fill proud or shallow. I let the knife slide over and the height is given by the surrounding surface. As the knife flexes and if you have a big hole - or in your case plasterboard with a void behind it - you will end up filling low if you do my method. Fine, a second fill when the first has set will bring it level. My sanding is not to reduce the height of the filler but to remove imperfections and particularly at the edges of the fill to blend it with the rest. I certainly overlap the hole onto the rest of the wall (back to the orange peel problem). Wine~o may have something there on how to fill the hole without spreading the filler :cheers: