Which Plasterboard (UK question)?

The ceiling is a cold roof (block and beam construction), insulated below with celotex/kingspan.

Should I be using vapour board or moisture-resistant board at 9.5mm or 12.5mm thickness?



Forgot to say: It's a bathroom

Update 2:

There were 2*2 battens fixed to the underside of the block & beams, which supported previous ceiling.


I've filled between and 2" of board over,( fixed with 75mm screws) (so 4" celotex altogether) .

Intention is to screw through the celotex to battens with 100mm plasterboard screws.

4 Answers

  • 8 years ago
    Favourite answer

    how thick the celotex ? with celotex the room should be warm enough without more insulation ..if block and beam ..how are you going to hold the boards up? how is the celotex held in position?..i will presume there is a lathe on underside ..12.5 foil backed ..ADD .why not add another 2x2 to existing 2x2..you still have your 100mm celotex ..and a solid timber to fix boards to ..

  • 8 years ago

    You should really include the thickness of the board when calculating the amount of insulation you need. However the thickness of the board is not important for any other reason, as the roof is inherently fire resistant. You need a Vapour Control Layer to prevent interstitial condensation, this would then cause the timbers to rot and your ceiling to fall down.

  • 8 years ago

    Since it's a bathroom moisture-resistant board at 12.5mm thickness.

  • 6 years ago


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