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Are these screws ok for OSB3 on my flatroof?

Discussion in 'Building' started by SS-ProjectBuild, 10 Dec 2020.

  1. SS-ProjectBuild

    SS-ProjectBuild

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  3. Funtimes

    Funtimes

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    Hi SS, I've done a couple of flat roofs and used decking screws (for OSB use a length of at least 2.5x the thickness of the board). Those linked are for internal use only.
     
  4. SS-ProjectBuild

    SS-ProjectBuild

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  5. Funtimes

    Funtimes

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    Yeah sound, something like that, think the ones I used were a shade longer at 65mm.
     
  6. SS-ProjectBuild

    SS-ProjectBuild

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    The screws are going into the firrings i assume and they dont need to pass through to the joist?
     
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  8. Funtimes

    Funtimes

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    You'll fix your firrings to the joist first and then the OSB on top so the screws will pass through to the joist at the thinner end. Towards the thicker end make sure the firrings are adequately fixed to the joist where your screws won't reach the joist.

    Alternatively you could use longer screws as the firrings get thicker so it goes through to the joist.
     
  9. ^woody^

    ^woody^

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    You need to avoid the screws indenting the surface too much unless you are countersinking each hole :eek:, so a screw with a wide "double countersunk" head (self cutting) would be better.
     
  10. SS-ProjectBuild

    SS-ProjectBuild

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    What glue do you recommend?
     
  11. Funtimes

    Funtimes

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    I didn't use any glue for fixing the firrings, just screws and countersunk the ones where the firrings got thicker.

    I'm not sure I'd trust glue on its own but I'm only a diyer so one of pros might suggest otherwise.
     
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