i am about to repair , or try to repair a hole in my plasterboard celing, but i am a little lost as to how i can do this. correct me if i am wrong but i was under the impression that when i cut back to the celling joists and place a new board in... it should lie back 2 or 3mm to allow for the finish to be applied .
But where i am missing the point or being just stupid if i put a 12.5mm new board to the allready 12.5 mm excisting board how is it going to lie back the 3mm needed to apply the finish as surley it will be flush.I know you can buy 9.5mm board but i was allways told for cellings it must be 12.5mm board anything less would crack .
Have you had a look at the DIY projects area of DIY Doctor: http://www.diydoctor.org.uk/projects.htm There are several projects relating to repairing holes in plasterboard and also plastering that may be of some use to you.
Hi rnd, if your ceiling has already been skimmed, when you cut back to joist and place say 9.5mm board, if 9.5mm board was what original ceiling was boarded with or 12mm if 12mm, the depth of the skim should give you your 3mm difference as the board you are using for repair has no plaster skim on it, so you can apply plaster and should be able to fill out to level.
If the ceiling was not originally skimmed over but joint taped and filled out using joint compound different application maybe need! unless you intend to skim whole ceiling?
How big is the hole you are repairing? if only smallish hole there are other methods.
If you need more help do not hestitate reply, I hope that the above info was of help.
thank's very much for the advice its been a big help.
the hole at the moment is around 18 inches as it stands before i cut back ,the celing is boarded with 12mm plasterboards . furthermore is it true what i have been told that a ceiling with pedestrian traffic above it, i.e, a loft conversion has to be boarded with 12mm board or it may crack, or is this just an old wife's tale.
with a hole that size your best option is to continue cutting back to joist and with joist generally being about 16 inch or 400mm apart you should be quite close to them.
I have always boarded ceilings in 12mm, I doubt overhead traffic would cause a 9.5mm board to crack any more than a 12mm board. But it does offer greater fire resistance.
Glad to be of assistance