Old cut-out piece of plasterboard screwed back in - how best to patch up?

fenwick458

it looks like a very tight and neat cut, so I don't think you'd have any problems with whatever you choose to use to fill it.
if I was doing the job I'd remove the board , locate the joist and mark them, refit and put plenty of screws in. (if you need to, add some wood to screw to before refitting, for example if at least half of the cuts are not on a joist)
and then my filler of choice would have to be drywall adhesive, mix it up very thin and squeeze it into all the joints, then just wipe over it all with a wet cloth. (dry wall adhesive is completely un-crackable in my experience)
then a few hours later just put easyfill of similar on top of it, and after that's dried sand and paint it.
but having said that, theres a 95% chance you could just apply readymix filler, sand it, and then paint it and it'll be ok and not crack, because it's a tight joint and it all looks smooth (from the photo)

Jeepers_Creepers

The two screws are in different vertical lines, so that suggests two studs behind there? You'll know when you remove it for a looksee :-)   

Yes, the 'proper' way is to add timber noggins at each side, half overlapping the cut board and the rest of the wall. Is this is an area where it might get bumped into regularly, or is this mostly a cosmetic job? If the latter, this is all you need to do...

1) Check - with a straight edge - that the cut board and the surrounding wall are on the same surface level. Remove the board - see what's behind it. If there are two timber studs/noggins there, then great. If only one, then fine, tho' not quite as stable.

2) Use a Stanley knife to bevel the front edges of both the panel and the surrounding hole - trim to around a quarter or half the board thickness, that's all. The purpose of this is (a) to remove all rough/fluffy/torn paper from the front of the p'board surface to leave a nice clean edge, and (b) to end up with a small 'V'-groove for filling once the board has been replaced.

3) Get some more screws - p'board screws are best, but ordinary wood screws will do. Mark lines on the panel to line up with the studs so's you'll get the screws in t'middle. Before replacing the board brush PVA onto the timber battens and also along all the cut edges of the hole and board. Refit the board, and screw in the two screws - and a few extra. If the heads of the new screws don't sink nicely below the board surface, then just tighten them enough to hold the board firmly against the battens and remove them afterwards when the PVA has dried - they shouldn't be needed any more (you may even prefer to do this so's you fill nice screw holes and not just a thin skim over the shallow heads).

4) Get some more PVA and brush it well into the V - go sideways across the slots to fill them, then along the slots to drive it in. Once you are happy that the mating surfaces are well coated and bridged, wipe off all the PVA that's on the top cosmetic surface with a damp cloth - you don't want any PVA on there when you come to fill and paint. Check that the board is sitting 'flat' in relation with the surrounding wall and not tilted so's one end is high and t'other low - you may need to brace a straight edge across it all to keep it level whilst the PVA dries.

5) Allow the PVA to dry fully. Fill the V with fine surface filler, dry and sand. Repeat with a second skim if needed.

FreeBear

Jeepers_Creepers said: 5) Allow the PVA to dry fully. Fill the V with fine surface filler, dry and sand. Repeat with a second skim if needed.

Nope. PVA should not be allowed to dry fully. Wait until the PVA has dried a little but is still tacky. this will promote adhesion between the filler and underlying plasterboard. If the PVA dries out, it forms a water resistant layer.

See this recent post after a plasterer had used PVA before skimming (plaster peeling off...) - https://forums.moneysavingexpert.com/discussion/6236189/painted-over-plastered-walls-which-seemed-dry-but-now-have-wet-patches

joe90mitch

Hi all. Thanks again for all the replies so far. Just unscrewed it and pulled it out. You can see the studs behind it in the below photo. The one that runs bottom left only shows about 1.5 to 2cm where the cutout will sit again - am a bit wary that might be too close to the cutouts edge and so might crack it? What do you reckon.

Am thinking the best bet is to screw top and bottom of the middle stud, perhaps a couple along the one that runs to the right, but do you think I'll need to introduce a baton on the left hand side and do I need to do something at the top right.

stuart45

Get some timber on the joints.

FreeBear

You'll need to fix battens all the way round the edge of the hole to support the PB when you fix it back in. The bottom left half is OK, but not the right hand side (nothing to stop the bottom bit of PB flexing).

Jeepers_Creepers

Love you lots, FB, but I have to disagree.

The purpose of the PVA in this case is to bond that panel in place, firmly enough to almost certainly result in a perfectly permanent fix. Hence it's applied to the timber battens so's the panel absolutely sticks firm and doesn't have to rely on just the screws (which can/will loosen if the panel is bumped in future) combined with the PVA which should fill the small gap and bond the cut edges back together. Between the two, that panel should be perfectly fine and ready for a cosmetic fill of the V groove.

Once the panel has adhered fully in place - ie once the PVA has dried - the gap can be filled without worrying about the gap moving or the board flexing, which would be a giant pita. The filler will adhere to the PVA. Why? Because it does, and also because the filler will actually slightly reactivate the surface of the PVA and make it the required stickiness again.

Yes Joe can add battens until the cows come home, but all I'm saying is - he doesn't need to, especially now we've seen what he has available to him - plenty supports there.

I'm not a pro in any trade, but have spent my life refurbishing my and various friends and relative's houses. I've done a fair bit of skimming (still rubbish at it, tho'), and something I discovered very quickly was that trying to skim onto 'tacky' PVA quickly descended into a comedy movie as the blob had no friction whatsoever with the slippery PVA so I was basically pushing it all over the walls with my trowel, trying desperately to flatten it out - to no avail. A quick surf revealed that it's ok to allow it to dry - it'll partially 'reactivate' later with the water in the skim. I did this, and the skim went on to the fully dried PVA beautifully (tho' my achieved the finish was still pants...)

I guess waterproof PVA might be different, as this might not reactivate. And, yes, perhaps I should have allowed the PVA to dry a bit more, but the point is, the applied PVA layer was nearly dry - tacky - but as soon as the blob of skim made contact it became slippery as 'ell.

I have commented on that other thread about the plasterer who may have applied PVA to the p'boards before skimming, but that's a completely different issue. What I suspect happened there is, the PVA on the boards over where the dabs were applied remained damp and active after the skim appeared dry, so the skim was still 'floating' on it.

It is important, however, that Joe - should he go this way - does remove all traces of PVA from the top surface of the p'board with a damp cloth, as any PVA here will reactivate when it comes to filling, and when he come to painting - both would risk messing up the neat job.

Grenage

Aye, add more battons along unsupported edges; you don't want any flex.
Then dampen the joins, fill and sand.  I generally don't use PVA unless I'm filling all the way back to something like brick.  I leave it tacky.

stuart45

Jeepers_Creepers said:I'm not a pro in any trade, but have spent my life refurbishing my and various friends and relative's houses. 

I'm different to some tradesmen, I find that people not in the trade often look at things with fresh eyes and are not bogged down with things drilled into them as apprentices and think they it's the only way to do a job.
I have found that I have learnt a lot from DIYer's.

FreeBear

Jeepers_Creepers said: The purpose of the PVA in this case is to bond that panel in place, firmly enough to almost certainly result in a perfectly permanent fix. Hence it's applied to the timber battens so's the panel absolutely sticks firm and doesn't have to rely on just the screws (which can/will loosen if the panel is bumped in future) combined with the PVA which should fill the small gap and bond the cut edges back together.

I'd suggest using a grab adhesive between PB and battens, especially if they are rough sawn - Much better gap filling properties and a stronger bond than regular PVA. Using a solvent free grab adhesive, a light squirt of water on the surface will make it a little more fluid.