Very exciting indeed!
I found this site:
http://www.naturbauten.org/index.html
It's in german and has some great video's on this topic. This guy is growing houses!
http://www.treedome.com/index.html
This is an English site but with less information.
His theory is that by grafting branches together diagonally, eventually the branches will become thicker, close the gap and become a solid wall.
I couldn't find examples of walls where this has already happened, but I think it's really interesting.
I put some willow cuttings in the ground arching over a small stream and will try to grow a bridge this way.
