I hear stories all the time about predators gettting into the coops around here on this board. here is a suggestion:
Heard a story about some local who put in a floor in an existing building- bags of concrete mix from the store. It was an old run down thing, not worth the hundreds to pour a floor, and a lot of work to mix in a wheelbarrow or tub.
So he dumps the dry mix on the dirt floor and rakes it "level" and sets the hose on it. and waters it carefuolly, voila! concrete floor.
i tried this myself though my tiny shed has divisions in it and each costs about 1 or 3 bags concrete. took me a year orr two to finish as i hd it to pick up the concrete. it probalby cost about 20 to 25 to put in an inchor two 10' x 16'
the spray of water has to hit a board or something or it digs a hole in the dry mix. A light spray is best to make it even but expect a very pebbly floor. you can always go over it with some fine mortar, same method.
my floor is very friendly (it waves) but is rat proof, and when the shed gets demolished then the thin crete can be broken up and thrown into a hole.