BiFolds in inner leaf?

[foundationer]

Question for you clever ppl:

Why are doors stuck in the outer leaf? Ease of weatherproofing?

Seemed more efficient to me to put them in the inner leaf with a nice rendered reveal on the outside but nobody seems to do that.

 

[Gazman16]

Maximum off the shelf external cills are 220mm as standard (you can get 250mm but only a few company's do them and they are not a color match to all makes). A 220 cill with a minimum 30mm external over hang would mean the back edge of a 70mm frame would be 10mmaway from the internal blocks. With a heavy door this can make fixing it impossible without non standard building practices.
Also why would you want to make your rooms smaller more expensive and harder to do?

And yes weather proofing comes into it too.

 

[foundationer]

They're all good points. Outer leaf it is.