Cavity tray behind vapour membrane?

[Moira Niedzwiecka]

Please can anyone offer some advice on where the cavity tray should be fixed?

External wall of the timber frame is OSB covered with membrane.

We will then have a 50mm cavity before the external ironstone.

Should the cavity tray be fixed behind the membrane and the membrane then overlapping the cavity tray so any moisture between the OSB & membrane is ducted outwards?

[Russell griffiths]

You've got it, imagine gravity pulling moisture downwards look at everything so it overlaps in a way that moisture will always have a pathway down and out. 

[Moira Niedzwiecka]

Thanks Russell.

I think I had answered my own question as soon as I had posted it.

I am just wondering what is the best thing to use. 

A preformed cavity tray similar to the Manthorpe one or taping some DPC to the timber frame under the membrane.

How would a plastic one be attached?

Would that be taped to the frame so water couldn't get behind it, or with some other fixing?