I have a coop and run on my back patio, the run is a dog kennel on the concrete. I have the top covered with a pitched tarp. I use straw in their run and a thick layer of it on top of the concrete. This has worked like a charm for me and once every few weeks I rake out the straw, hose down the concrete, let dry and refill. IN the coop I use pine shavings. It helps that they free range everyday so they dont use the run often unless it's rainy outside. Their beaks stay nice and trimmed up as well as their toe nails from filing them down on the concrete.