We're working on the foundation of our run which will be >32SF for 4 standard hens (they'll get some general yard time in the afternoons outside the run -- too many cats want them for a snack when we're not around). Anyway, I've been laying large pavers on which to set the wood framed walls later.. The grass is dead due to a recent remodel and I've been basically removing the remaining grass from the run area as I go.. Is this OK for the birds once they're ready to go or should I consider planting grass in there before they move in? I think I read somewhere that they will destroy grass in a run that doesn't move... Is this correct? If no grass, do I need anything in the bottom of the run aside from hard-pack dirt? Thx!