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this relates to a previous question that I asked here: making good a hole in plasterboard

I've patched a hole in some plasterboard, which is against an external wall, by gluing it to some wooden strips that the surrounding plasterboard is also glued to.

hole waiting to receive patch Patch glued in place

To the left and right, the patch is level to within a mm of the surrounding plasterboard. The trouble is in the middle at the bottom where the patch in inset by about 2mm.

Plasterboard bows out relative to patch

The patch itself is flat, rather the plasterboard bows out a little. My concern is that the next stage in this is to apply fibre glass jointing tape and the surface it needs to attach to is now uneven. I'm unsure if I should apply a plaster skim to the patch to get the level up before applying jointing tape and then skim over the top or to just lay the jointing tape as is, which will either leave a diagonal slope over the patch or result in a fold as it goes around the corner of the 2mm ridge.

I've never done this before and I guess part of my uncertainty is I don't really understand the role of the jointing tape. Why not just apply plaster across the lot without it?

Advice is appreciated.

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The role of the mesh tape is to prevent cracking of the compound when it dries and if there is any movement of the joints. All that matters is that the tape is embedded in the compound, it does not have to be at a particular level. Slap some compound on first to get deep into the joint. You may want to notch out the joint a bit first for better adhesion and to clean up the paper edges - use a box knife to create a "V" notch. Lay the tape over the joint (don't overlap) and lay a thin layer of compound over it to make sure it's embedded nicely. Let that dry and then you will need a few coats to bring the patch to level with the existing surface.

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  • Thanks DJ, I have a couple of questions which might seem odd if you've done this many times. I bought the fibreglass jointing tape in a roll but haven't started unravelling it; i imagined it would be self adhesive, but you think it requires compound to stick? Second question is, the jointing compound seems to only want to be layered on 5mm thick max; if I embed it into the joint then that could go far deeper (12 mm). Should I be doing this in stages to keep the depth down?
    – aghsmith
    Commented Oct 31 at 0:27
  • Yes you do it in stages, And yes you can stick the tape on dry if you like and push the mud between the mesh to force it into the joint. I just like to get as much as possible into the joint first but that's just my preference.
    – DJ.
    Commented Oct 31 at 0:31

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