Scottish roof (ply under tiles) in England...help please!

[Allthegearnoidea]

Evening all,

 

I would be grateful for a bit of help if anyone has any knowledge in this area!  The structural engineer has specified a 12mm plywood skin on our single storey rear extension with mono-pitch roof.  I'm planning to use BMI Redland Mini-mockbond tiles, as they're closest to the tiles on the main house and can handle the low pitch (17.5°).  

 

I'm at the point of building up the facia / soffit, but with the vertical battens necessary over the ply skin, I'm struggling to visualise the facia / guttering arrangement.  My CAD mockup shows the water is going to overshoot the gutter, but if I use a taller facia board I'll be blocking the breathable membrane, which needs to sit either on top of the ply or on top of the vertical battens (it will probably be Tyvek Supro if BC are happy with it, as the data sheet shows it's used for this sort of build up).

 

 

Any of you knowledgeable folk know what to do here?

[Allthegearnoidea]

Perhaps cut a proper tilting fillet and mount the gutter to that where it overlaps the vertical battens?