Fixing plasterboard over celotex

Discussion in 'Builders' Talk' started by wb1627, Oct 26, 2009.

  1. wb1627

    wb1627 New Member


    I'm fixing 12.5mm foil backed plasterboard over 45mm celotex insulation in an loft conversion. There is also 100mm celotex in between the rafters. My plan is to fix the 45mm celotex to the rafters with nails to hold them in place then use 100 mm drywall screws to go through the PB and the 45mm celotex into the rafters. I don't want to use battens as I want to achieve as much head height as I can. Does this method seem reasonable and how many screws would you suggest I use per sheet? I reckon about 40 or so?
  2. Dear Wb1627,

    Try using Everbuild Dry Fix it's magic! You squirt the stuff on the back of the plaster board around the edges and across the centre, leave for 5 minutes and then press the board onto the Celotex. Make sure the the board surface is Celotex surface is dust free.It sticks like you know what.

    Video demonstration is easy to find on U Tube or Everbuild site.
  3. lamps

    lamps New Member

    if you have one layer of celotex why do you want another?
  4. wb1627

    wb1627 New Member

    I'm using 45mm over 100mm as the 100mm is inbetween the rafters and the 45mm faces over it. It has been stipulated by building control (and seems quite popular looking at other blogs)
  5. wb1627

    wb1627 New Member

    I have never used 'no nails' or similar. Thanks for the post but I prefer old fashioned nails and screws, particularly for something as big as this!!
  6. geraldthehamster

    geraldthehamster New Member

    Your method sounds sound. I did something similar (75mm PB screws through PB and 25mm Kingspan) and it's solid. I put screws in about 300mm apart, but perhaps someone who actually knows what they're talking about can give you better advice ;)

  7. nearnwales

    nearnwales Member

    why can't you use insulated plaster boards saves you doing it twice
  8. nearnwales

    nearnwales Member

    you want 6 screws in each row on a 8x4.
  9. dryliner essex

    dryliner essex New Member

    CL how are you going to fix the celotex good enough to stick p/board to it ???????
  10. imran_

    imran_ New Member

    Sounds fine. If you tape the celotx edges I don't think you need a vapour barrier as well???
  11. wb1627

    wb1627 New Member

    Thanks for the advice. I was reckoning on about 40 screws per sheet...... sounds a lot but I don't want it moving. I will tape any seams too, but building regs stipulate foil backed PB and the difference in price with non foil backed is minimal. Better off doing it right at the start that trying to remedy a problem later.
  12. jedwood

    jedwood New Member

    100mm drywall screws are fine. the celotex just need to be held in position and the screws do the rest. I'd say 5 screws across the width of the board on each joist - if it needs 40 'cos there's 8 joists so be it!

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