my girls shed has a concrete floor so it gets really cold (great in high summer though) I use a large piece of fake vetbed (from Wilkinsons) on the floor, plus large litter boxes full of hay for eating, and megazorb litter, which keeps it dry. Quite often though, they sit on the cold floor next to the door - and they chew and dig the vetbed too, so I'm glad it's a cheap lookilike!