I'm a research nut, so before we built the coop, I crossed referenced problems with coops from every aspect conceivable. We don't put any water or food in the coop except for harsh weather conditions (like 7-degree temps). We used decking, then coated it twice with a food grade sealant, then...
White plastic made for walls at Home Depot does the trick. We (almost forgot to add, we applied a sealant first to the decking) then glued and screwed them down tight, then added fine hemp mixed with potting soil for moisture control which has worked beautifully. No scraping and only will...