Patching plasterboard - joints?

[Lobster]

An existing stud partition has a large bit of plasterboard which needs replacing. I've cut a new piece of board to fit the hole. Question - do I cover the joins? Do I use jointing tape as for a new wall? The issue is that the old boarding has been skimmed, so if I apply tape it will create a raised area over the joint. Do I just have to live with that; ie, and re-skim the whole wall so it has a thicker layer of finishing plaster to 'bury' the proud tape? I've tried picking off the old skim layer around the join without much success.

Thanks David

[BigWallop]

The existing plaster should be cut back to at least 50mm away from the new edges you've created and then skimmed over so the whole patch is smoothed to blend in with the original skin. To remove the existing plaster skim is easily done with a model knife. Just make a cut through the skim and not the whole depth of the plasterboard, then tap it with the handle of the knife so it chips off along your cut.

[The Natural Philosopher]

V notch the join and just use bonding plaster in the groove.

Then skim.