I have saw on here were allot of people have problems with muddy runs and drainage problems + smells. My solution came by accident- I started my chickens out in my old gravel dog runs. I have not had any problems with drainage or smell. The past two years I have been puting hay on top of the gravel so it would be softer on there feet. Plus with this method you get free grit. I'm starting to think the hay was a bad idea because I'm starting to have a problem with smell. I'm thinking about just puting another layer of gravel down on top and forgeting about the hay. My chickens free range most of the time so I don't foresee any problems. My question is does anyone use just gravel in there runs?