I couldn't have a dirt floored coop because where my coop sits isn't level. So my coop is raised with 3/4" plywood floor that we already had. I was going to put vinyl down, but I found a 4x8 sheet of wall board that goes in a shower surround up in the top of my garage. It was slick and waterproof like vinyl, so I used that instead. I had to buy another sheet and found it at Lowes for 12.00. I nailed it down with those short roofing nails with the big heads. Works great. Now...I just built my coop last July so I don't know how long it will last, but I keep the waterers in the run and so have had no issues with water inside the coop. I have 6-8 inches of shavings in the coop and a poop board under the roost. I also use shavings on the poop board with a little Stall Dry or Sweet PDZ for smell/moisture control and also sprinkle DE on occassion, makes for easy clean up. My run is a pvc hoop run that is covered with a tarp so my run doesn't get all wet and mucky. I can keep their feed and water out there with no issues. I made two Christmas cookie tin water heaters for my plastic and metal waterers, they have worked great! My house has no insulation or interior walls so wasn't able to extend the flooring up the walls. It sounds like what you have planned will work just fine!