I have a raised wood floor with vinyl flooring, with wood shavings for bedding. It works great, but I had to make sure every opening was blocked against the rats. My coop also withstood a furious raccoon, who screamed and shook the door. (I slept through this, but my neighbor did not.
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My DSO has a dirt floor in his coop. He doesn't have problems with moisture, but the rats do get in, eating feed, and occasionally eggs.

My DSO has a dirt floor in his coop. He doesn't have problems with moisture, but the rats do get in, eating feed, and occasionally eggs.