coop run extension

Wondering what to use for the "flooring" of my chicken run? It's currently dirt, but I am worried about the upcoming winter in northern MN. More dirt? Hay? Sand? Leaves? I will soon have access to a ton of leaves... not sure if that's a great option or a slippery messy one. :) The run is covered...

I have a coop/run that is average size and fits about 8 chickens. The run part of it is not really big enough to leave the chickens in for any length of time. So, I am looking for a run that is around 4.5' to 5' high, and about 8-10' around. Well, in my search for one, I have found some really...