I dont think it is mandatory to paint but I would highly recommend it. I used Impervo which is a hard enamel paint that I used for the interior trim in my house. In my old coop I used it on the floor and walls. For my new coop I used it on the walls and the poop board. The last thing you want is for the floor to get damaged by water or aggressive cleaning, the paint really helps to protect the wood. It is amazing how a few chickens can really dirty up a place. Just the other day my waterer in my brooder leaked out all over the floor and another older chicken had a broken egg and a some diarrhea. The stall mats work great but if moisture got trapped underneath it could be a real problem if the wood was unsealed.So do you think I could add the horse stall mat over my plywood coop floor instead of painting it for protection. I'd like to try to avoid any kind of paint only because I know it can be toxic to the chickens especially when it's first applied.