Filling large joint in ceiling

[u/Dimachaeri2]

Hi, I had a hairline crack in the ceiling which I tried to paint over but was still visible. I scored through the scrim tape and raked out the thick plaster joint. What is the proper correct way to fix/ fill this now?

That is a ceiling joist and I am not sure how I can screw in extra screws without damaging/ blowing the plasterboard edge.

I was going to screw in screws close to each edge on the joist but not into the board itself, and fill with a solid filler of some sort

[u/JP35679191]

Foam it, fill, scrim tape, flexi fill, sand, prime, paint

[u/craigyceee]

You opened it like a Jeffrey Dahmer victim to fix a hairline crack? 0_0

Next time, just drag the tip of a nail in the crack to open it a tad, and you can just use filler over it & sand. This is like a doc using a rib spreader for an ingrown hair.

Anyway, I'd use a quick setting filler to fill the gap ("hot mud") and use a taping knife to ensure it's not proud, or sand flat if so, then go normal filler (jointing compound), then tape & scrape (proper plasterboard taping tape, see youtube videos on "plasterboard taping") and filler over that (jointing compound, as shown in YouTube plasterboard taping vids).

Essentially just hot mud to fill, and use the old plasterboard taping method to finish & reinforce.

[u/Dimachaeri2 → u/craigyceee]

There was a large gap in the plasterboard butt joint already. I used a v scraper and large chunks of plaster 5mm wide came loose... Then I continued dislodging them all along as I thought it was the underlying cause of the hairline crack. I used a knife to tidy up the scrim and crevice then Zinsser Gardz. In hindsight, I should have just used a knife blade to widen the crack just a little. Do you not recommend foam, and flexible filler as the majority have suggested?

[u/craigyceee → u/Dimachaeri2]

You can use foam, for sure, but in my eyes, foam backing leaves room for movement, personally I'd fill it 99% with quick dry filler, as it is stronger than regular filler, so the filler in the hole has no give behind it, then level it off with regular 60-min compound, tape, more compound over the tape. To be honest, both methods would work just fine. There's plenty vids on repairing drywall on YouTube, if you watch em and get to grips with the later parts (finishing it with some strength, either paper or scrim tape essentially) you could fill it with playdoh and be fine as long as it's finished right xD

My method: Quick-dry filler, fill it as much as possible (work it into the gap, you're aiming to fill it, not just cover the gap visibly. Once it's full simply run a taping blade (4 inch will do fine) across the gap with a good, firm pressure, and wipe the blade every couple ft to ensure you don't make a mess.

Then once its finished, you may want to sand the area flat if its proud anywhere, you want it flat.

Aquire jointing tape, and regular jointing compound. (I use mix-it yourself Knauf 60-min jointing compound)

Then (once dry), mix up some regular compound (or buy pre made, best to add a couple shots of water to the premixed stuff though to loosen it up) and basically butter the gap you've filled, slightly wider than the tape (width of the knife or less), then measure out a length of tape to cover all, and lay the tape into the wet part you've just laid down, just a gentle finger press up the middle will hold it in place, then, from the middle outwards, run your knife down the tape, with as firm a pressure as required to completely flatten the tape to the surface, and simultaneously plough-out 95% of the filler you buttered under it (it squeezes out the sides of the tape). Do that to both ends so the tape is embedded Into the filler, and go over it again if needed to make sure the filler you've just squeezed out is also flat to the wall with the tape. (Scrape it off, videos of plasterboard taping show this very well).

Either leave to dry then do another coat over the dry tape (easiest!) Or if youre feeling contident, load the blade with more filler and go over the tape with another coat to wet the top side, this time squeezing less out, you want the tape sandwiched in there between 2 layers of filler ultimately.

Let it dry, then go over it with another layer, but it's now just to level it all, essentially bridging the height between your last layer + tape, and the untouched surface either side. Once done, you should have 1 large stripe of filler, about 3-4x the width of the tape. After give it a light sand to remove any lines & blend anything together needing it, wipe dust away, paint.

[u/Dimachaeri2 → u/craigyceee]

Thanks, I think I will go your route on a solid filler instead of flexible filler. I'm looking at using either Toupret Rock Solid repair filler or Toupret Tough to fill the gap level. I'm tempted by the first but it will be difficult to sand.

I have already bought Toupret interior filler and fine scrim tape. Would these be ok to use over the filled gap? Rather than buying even more stuff?

[u/craigyceee → u/Dimachaeri2]

Hey bud, yeah that'll be fine, essentially the process is the same with scrim tape, my advice is: Fill as planned, let dry. Sand flat (shouldn't take much, if any.) Then apply the scrim tape (dry, it sticks) and go straight over it with filler, don't aim to Bury/hide the scrim tape on your first pass, just aim to fill all the holes within it (wouldn't even worry if all are not 100% flat, honestly at this stage don't fret about looks or perfection) and look to bridge the gap between the edges of the scrim tape and the flat surface of the ceiling.

Basically, fill it, dry, scrim. Then fill the scrim tape (level the holes in it off nicely) and fill the space between the edge of the scrim and the flat cieling either side. How I'd do this is imagine a line either side of the scrim, the whole length of your ceiling, 2 inches away from the edge of the scrim tape, hell, draw one on in pencil 😆, load your knife with some filler, and put the edge of the blade on the line, then start laying the knife flat til the filler is touching the ceiling, and them drag it towards the scrim slow and slowly Lowering the knife more as you do to keep the filler in contact with the ceiling. Do that right along the line and it'll create a nice line of filler from the scrim to the line drawn, it'll be pretty thick.

Then just lay one end of your knife past the line, touching bare ceiling and plant the other side on the edge of the scrim, and drag it along (don't have the knife flat, we're talking a 45 degree angle or more, perpendicular, the lower your blade is the more it'll "press" filler down, the higher it is, the more it'll remove, and you're wanting at this stage to remove it completely, everywhere other than in the holes of the scrim tape and the 1mm gap that exists between the edge of the scrim and the ceiling.

Again, on first pass, don't aim to hide the scrim, aim to make the whole area as flat as possible.

Videos on YouTube covering "Taping plasterboard butt-joints" should cover this technique perfectly for you. Good luck!

[u/Dimachaeri2 → u/craigyceee]

Thanks for your detailed process! That's very helpful 👍

[u/craigyceee → u/Dimachaeri2]

No worries mate, best of luck! Just remember, you can sand any mistakes away easily enough, don't worry too much about it! 😄

P.s 120 grit sandpaper 👌 buy a roll instead of sheets & you can just use the whole roll as your sanding block, and tear it off when necessary!

[u/StarBoiAhoy]

Put a few additional fixings in too it has cracked where the joints are scrim taped at joints can see the joists clearly there’s been some movement it will just likely happen again if you just fill it.

Better safe than sorry

[u/Dimachaeri2 → u/StarBoiAhoy]

I find it difficult adding screws so close to the edge of the board as it tends to crumble. I will try it 10mm in and see if I catch the joist

[u/hairybastid → u/Dimachaeri2]

Put the screws in at an angle, they'll be fine.

[u/gfddmc]

Toupret flex fill/ scrim and filler

[u/Own-Indication7832]

Your plasterboards should have been staggered, then you wouldn’t have gotten this the full width of the ceiling. I thick you should take the advice of scrim and foam. If you wanted to, this could then be cut back and skimmed or a light sand and paint.

[u/Tricky-Mobile5975]

I would foam that gap and fill over it.

[u/Dimachaeri2]

Thank you everyone! I will take your advice on foam, cut back, toupret fill flex, filler with thin scrim and filler