That's similar to what I'm doing. Mine's about 2' deep and I only have 5 birds. I periodically fork down deeper to loosen the soil and give them access to giant grubs. The soil at the bottom is so much richer than it used to be.
Thanks for posting this! I saw that video when I was designing my coop and incorporated some of that design into mine on a smaller scale. I dug down and built the coop on a foundation of rows of cement blocks. It's not as deep as a meter but it still works really well!
