I would build the BIGGEST coop/run area you can/allowed Chicken Math is terrible and when the time come, easier to downsize than enlarge. The minimum space often recommended is 4sq ft per chicken in the coop & 10sq ft per in the run. When Hubby built my Chicken House he went 8x12x7=96sq ft, my figuring is 14sq ft per so limits me to 6. I've since had 5 Wyandottes with no squabbles but won't keep more than 4BOs as it "feels" crowded to me. Helps keep me from getting carried away I know HDPE ... Didn't know what it was called, Hubby used it for his boat & I used some to line my poop board. Great stuff I do a modified DLM on clay dirt floor, girls are confined ... Toss in shavings and that's in. No leaves (here) like you all have so I basically use shavings & toss in grass clippings when I mow the lawn. Pick up the big stuff & they mix it up scratching. Just keep adding more shavings as needed, cushy makes for less chance of Bumble Foot. Maybe once or twice a year I rake out some out to fill low areas or spread in the yard, works for me.