I can be so stupid sometimes. I thought it would not reach the sub structure. Thank you.
There ain't nothing stupid about posing a question or thought...and whether the DE is still viable at earthworm depth is questionable, but there's a lot more good bugs than just earthworms.
I'm sure there are others that would defend the use of DE. It all depends whether you want to establish an ecosystem within the coop/run that will naturally handle the chicken manure and add some health/nutritional benefits. Best wishes,
Ed