re: Bonding a warm roof, polythene VPL

[MisterBoy]

This old post covers almost exactly my situation: https://www.diynot.com/diy/threads/bonding-a-warm-flat-roof.406838/

Except I have very shallow pitched roof but same scenario. Joists, 22mm subdeck, cheap polythene (Visqueen?) VPL, 120mm Ecotherm, 22mm OSB top-deck.

Like OP I have fears about putting load of holes in my VCL and my ability to hammer/screw through 165mm and hit the joist!! He started his thread asking about bonding his roof and I'm in that exact same position. Sounds great except I worry how to strongly bond my VCL to the sub-deck and the PIR. fears of the whole roof peeling off!!!

OP was advised not to bond but use very expensive fixings. Would welcome advice how to do this given it will be done by handy person but not a roofer. Bond or screw or nail? How are InsoFast better than big old woodscrews - how many per 2400x1200 sheet is enough?

Tx

 

[MisterBoy]

Looking at them fixings, they talk about counter battens: https://www.ancon.co.uk/products/wall-ties-restraint-fixings/the-staifix-range/warm-roof-nails

Not seen this before looks like instead of a top deck you just use battens. Then put your tiles right on top?! Doesn't sound great for walking on later or am I mistaken... Wouldn't an outer OSB deck be ok?

 

[MisterBoy]

BC chappie demands a dedicated VCL which makes bonding sound a bust if you cant bond to plastic VCL. Other VCL seems a lot more ££ unless anybody can recomend something.