I have been around several different types of commercial bird houses.
The one in my backyard (my mother's - she raised parakeets (2k breeding pair)), had a cement floor. We would cover it with sand. Once a year or so, we would do major cleaning (I assume after a molt - I was a kid). Every box got washed and scrubed, floors jot scraped and new sand was put in it. It is a warehouse now - hard to tell it housed all those birds for 20 years or so.
When I was a little older, I cleaned pullet houses. They had a dirt floor - but the poop would get an inch plus thick. We would use pitch forks to get under the poop, and would stack layers of it caked on the fork untill it was worth throwing it in the trailer. I think when we built them, they had a cement beam supporting the exterior wall - no digging under that. (I did not help build those - I did help build other dry houses. The dry houses did not use cages).
I also helped build wet houses. Those are the laying houses that everyone associates with the evils of commercial poultry. The floor was all cement, with troughs and walkways. The cages were hung above the troughs, so the poop that fell could we washed out. Since those houses were secure - I think they used a fairly large mesh wire.