Husband and I are working on our coop, and after reading everyone's posts about the benefits of a sandy run, we're thinking of doing that. A lot of people seem to suggest boxing in the run floor with pressure treated wood, but I have heard that the chemicals in it aren't good for the chickens. I also was wondering if it breaks down--even pressure treated it's still wood buried in the ground! We were thinking instead of using cinder block (with gaps between for drainage) lined with that pourous gardening cloth (although now that I think about it--it's probably chuck full of chemicals too. hmmmm). Anyway, I'd love your opinions!