If you don't have any run litter at all, the run can get quite poopy and gross, and muddy when it rains. And it will freeze solid in the winter. If you are up for regular cleanings, that can help the poopiness issue, but it will still get muddy or frozen. I have a very low maintenance setup where I never clean the run, and it never gets poopy or muddy. It only ever freezes if it's exceptionally cold (single or low double digits). I have a deep layer of organic matter of different sizes and textures - wood chips, dry leaves, grass clippings from mowing, and other miscellaneous yard waste that I rake up from my yard. The nitrogen in the poop mixes with the carbon in the plant matter and forms an active compost, which the chickens stir constantly. It doesn't smell, and I don't have to clean it. The larger particles (wood chips) provide great drainage so it doesn't get muddy and there are no puddles after a rain. And, again, because of the good drainage, the top layer dries fairly quickly and doesn't freeze in the winter. The deeper layers that stay wet longer will freeze, but the top usually stays loose. I got my wood chips from a dead tree that got shredded, and all the other material is yard waste, so everything is free. I collect dry leaves in the fall and use them throughout the year. I top off the run with leaves or wood chips as needed, and throw the clippings in there every time I mow the lawn. I love this method and highly recommend it!