Fixing plasterboard to plasterboard

[Conor]

Hello all

I have a bathroom which has insulation backed plasterboard on the ceiling, I'm going to need to put new plasterboard under the existing plasterboard. What would you suggest I use to fix the new board to the old one?

I'm guessing a screw just through both bits of plasterboard won't be sufficient, will I need a very long screw to get it up into the wood above? If I do this what are the reasons for not using a standard easily gettable long screw over a long plasterboard screw?

Sorry for all the questions, I've been doing some searching and can't find too much.

 

[Richard C]

Your correct in that you can’t just screw into the existing boards, it will fall down pretty quickly. Normal method for over boarding is to screw through both boards up into the joists above providing the joists are sufficient to take the extra weight. Don’t use ordinary screws, use the correct drywall screws.

Don’t know where you’ve been looking but they are readily available in lengths up to 100mm from local builder’s merchants, B&Q & from Wickes/Screwfix (where I usually get mine) & there are many more on-line supplies like this one;
http://www.leofixings.com/productde...e=242&hdnGroupCode=2758&hdnProdCode=QjfEDDSgO
How thick are the existing insulated boards?

 

[Conor]

Thanks for the reply.

I've been excavating and found that the boards that are up there are only just over 30mm, I had thought that they where thicker, so your right that it shouldn't be a problem to get long enough dry wall screws.

Thanks.

 

[PrenticeBoyofDerry]

30mm plasterboard?
Could it be lathe and plastered ceilings, 30mm seems a bit thick for plasterboard, even if it's had half dozens layers of skim on it, unless it has already been over boarded?

 

[Conor]

Sorry for not being clear, the plasterboard and insulation attached to it is 35mm thick, not just the plasterboard.

 

[PrenticeBoyofDerry]

Are the boards fixed with the thermal insulation removed around the timber joist so plaster surface straight to woo or are the fixed with insulation sandwiched between joist and plasterboard, So you need a screw that will fix 12.5mm board carry through 35mm above and at least 35mm into stud. you can get 100mm dry wall screws.