Flat warm roof construction

[Benway]

I understand the layers of a warm roof.

GRP
18mm OSB T&G
130mm Celotex
VCL
18mm OSB
Firrings

But what do you screw all this stuff down with? A nice long 200mm screw through the whole lot?

Thanks.

 

[Notch7]

We generally use 180mm x 6mm csk pz3 screws on 125mm celetex.

 

[^woody^]

The furrings are fixed to the joists and you don't need to fix the deck through them into the joists - well at least at the thick end.

 

[Benway]

But the deck does need to fixed somehow. The question was if long screws were the way forward.

Cheers.

 

[^woody^]

Yes you'll find that screws are better than glue, but the point is that they will only need about 50mm of fixing into a joist or a furring and do no need to go in to the joist at the thick end of the furring. So yes 200mm may well be fine

 

[Benway]

Thanks. Can't go the glue route as my vapour control layer isn't fixed to the lower deck. Off to Toolstation I go!