RSJ x Tony tray

[Olf]

On one end of the extension (at the existing building wall) the roof joists are suspended from an RSJ, that creates a new challange: junction of the beam and the wall.

 

With the load imposed by the beam I'm worried that any membrane I'd try to use to form 'Tony tray' would be thinned to the point of becoming permeable, defeating the whole point.

 

The other issue comes from the small size of section of the wall requiring this treatment - that effectively makes it a 3D 'cup' around the RSJ end to be formed. That got me thinking about using joist seals, has anybody tried that route?

 

Actually '3D' aspect should also show at the ends of standard 'Tony tray' - would you fold & wrap the membrane at the end of the wall, or for simplicity just leave this one junction potentially leaking?