I also have concrete floors in my coop & run's, I live in an area the devil calls home when it comes to the weather. The concrete is so easy to clean, and maintain. The chickens think it's great. I have never had any sickness or disease with my birds and I like to think it is because I can keep the whole area disenfected. After I shovel and sweep up, I then hose it out pour some bleach on the floor and hose out again. I poured it so it wiil drain very nicely. I don't know why more people don't do this, Maybe they think it's to difficult or expensive, Plus since I don't have a dirt floor I can spray down walls and nest boxes twice a yr without having a muddy mess. My coop is 12'x22' with 2 runs 12'x12 each both coop's & run's are cement floors.
AL