# Forum Home Renovation Plastering  Best way to plaster and cut gibboard for ceiling that has to be dead flat

## Renovate2019

hi, 
i have a ceiling that is below the other part of the ceiling and which was dead flat and needs to be again after repair and replacement of gib board and plastering.
What is the best way to cut the gib for plastering, so that the result is dead flat at the joins? Would it be a good idea to cut all edges (for joins) so that it is tapered to allow for the tape and plaster? The edges would then be very weak and chip off if they are screwed? It would then be very hard to plaster??  
I am going to use the sticky fiberglass tape 
thanks

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## phild01

Difficult to understand your issue but I take it is a patch repair of a plasterboard ceiling. Back blocking and not using fibreglass tape (instead of paper tape) is the best approach.  Seldom are butt joints perfectly flat but with wide blading of the base and final coats will give an undetectable result.

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## Renovate2019

hi Phild01,  
Thanks for your response.It was a definitely a patch repair.My issue was that i had to cut the gib so that the edges were tapered it so that the finish would be absolutely flat to the existing gib as there were cupboards that had to open and there was only several mm clearance,and thus i had some deep gaps to plaster at the joins where the tapered edges cracked off,and the plastering was cracking in the first 2 layers of plaster i put on but i think the 3rd will now not crack at all.Thanks for your recommendation of the paper tape. There is also a light there that seems to show anything not flat on the small ceiling,so i was wondering what the plasterer had done to make it dead flat.Was it dead flat?? It looks like it to me.(?)  
thanks

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## droog

If you need the plaster to be dead flat with a butt join you need to put battens behind the repair with packers so the screws will pull the edge of the sheet below the rest of the surface.
I will see if I can find a diagram of what I mean.

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