New strip/membrane details

[pudding]

Hi,

 

Attached is a current sketch detail of my new extension slab/wall junction, with radon/dpm membranes.

 

 

Had a meeting with builder/structural engineers last Friday. They, especially the builder, were keen to take the radon membrane back down the outside of the lightweight block and underneath the EPS/concrete block (think mainly as he thought it would be less fiddly and easier to do), and then wanted some kind of cavity tray detail with the DPM and were concerned about water getting in through the bottom of the Pavatherm. They mentioned maybe taking the current DPM back under the timber soleplate, and then maybe using another piece of plastic to form some kind of sloping out cavity tray. Like this:-

 

 

Any suggestions or comments on either?

 

Cheers.