It can't be long now - life for both parents seems solely about feeding the babies, and I have seen the little ones standing on the beam the nest is built on, and flapping their wings. Their first flight could be very difficult as the closest daylight is a "window" covered by chicken wire, and the floor of the granary is still completely covered in building materials.
I wrote the above on Wednesday: yesterday morning I walked into the granary and it was silent, and the nest empty. All except for one tardy soul who had made it to the next beam and was peeping pathetically. A couple of hours he was still in the granary, with mummy sitting on an onion box outside and making encouraging noises.
It's big and scarey out there...