Cavity Tray Experts required...........

[Bob6789]

We've got a flat roof (original build) which has leaked at the abutment for 8 years (since new) despite many remedial attempts.
Our rear offshot has a ground floor extending about 2m further out than the gable end on the 1st floor, so in effect we have a full width aperture below the gable wall.
The flat roof abuts the gable wall for the entire width.

The big question is....does the cavity tray design make sense to you?? See pics.
The design uses a one-piece membrane, but there are no stop ends used - instead, the membrane is mortared directly into the outer leaf of the wall.
As you can see - it does not slope down towards the outer leaf as it moves across the cavity into the outer leaf, at both ends.
NB: The mortar gap shown was filled correctly at the time!

It seems to me that water easily can track to the underside of the membrane? (= disaster).

Expert opinions welcome.

 

[^woody^]

Is that thing chased into the inner leaf? It should be.

 

[Bob6789]

There's a plastic angle bar chased into the inner blockwork, then Protan membrane is welded to that.

 

[^woody^]

If the ends are inserted into wall ends or returns as you seem to state, then it should be fine as long as it is above the flashing on the external leaf and there are weep holes at least every four bricks.