Flat Roof VCL and Closing Cavity on Parapet Wall?

[Woody3]

I'm about to order the materials for my flat roof (2 x layers 18mm OSB3, 120mm insulation, VCL, etc).

My material supplier has asked what I want to use for the VCL, and to be frank, I haven't a clue. He said I can use 500gauge polythene or polythene with a reinforced grid or a more expensive foil/reflective membrane . Is standard 500g polythene ok to use? Or do I need something more expensive?

I will be installing foil backed plasterboard to the ceiling if that makes any difference and it is of warm roof construction.


Next question - I need to close off the cavity on top of the parapet wall. Obviously the cavity closer will also be used to support the roofing membrane underneath the coping stones. I've been to my local cavity closer manufacturer and they don't make anything that is wide enough for me. I need something that is suitable for a 100mm cavity and has 50-75mm "leafs", so around 200mm overall. Are there any alternatives that I can use to close off the cavity?

Cheers!

[astroarcadia]

500g poly ok for VCL.

DPC to close cavity with 18mm WBP ply, depends on the roof edge detail. Will there be an edge trim/profile/drip?

Edited by astroarcadia on Monday 31st August 07:48

[roofer]

http://youtu.be/HoLHb7ptGfI

As said cap cavity across its width with ply/ Osb and the upstand as well.

[BigRickus]

I would have thought a length of thermabate could close the cavity, defo available at 100mm. Ply would make the joint under the coping stones write chunky. Would have thought the roof membrane may be suitable to close cavity though if it laps under the coping stones??

[Woody3]

Thanks chaps. Found a cavity closer that has wide enough "flanges".

I'm going to use 1200g dpm for the VCL - seems to be somewhere in the middle in terms of quality and I have two rolls of it in the container.

Cheers again!