I'm in the process of converting my old 20'x16' 3 sided horse shelter into my first coop. I live in northern WI where winters get to -20*+ before windchill. The shelter currently has a dirt floor. Should I leave it and just add some bedding on top? or put some pallets down and lay some linoleum on top? I would imagine the pallet idea would rot and cause a mice problem. Any suggestions?