I had a coop basically on the ground - just 2.5 inches above it - which I thought was clever until I needed to clean it. Not directly on ground, good, but less than 3 inches above it gave rodents a very nice haven.
All the coops I've built or bought since have been elevated. One is 8x4, so it's only elevated the height of concrete blocks, which means I will have to get on my belly and use a rake or stick or something to chase out any chickens who have taken shelter there. However, I've been lucky in that none of the chicks, chickens or bantam chickens have needed to be retrieved from under that coop. They may go under there on really warm days to chill out in the cool dirt beneath it, but always come out to go to their respective coops to roost at night.
Elevate your coop(s).