I built my playhouse coop out of a little tykes playhouse. I put a wood floor on it and did my best to seal all windows etc. I've been using pine shavings about 4-5 inches thick and after a while the bottom gets very wet. Last week I switched to sand to see what it would be like. I'm not sure if rain is somehow getting in but in some areas the sand is completely soaked and I am getting what appears to be mold. The mold seems to be growing literally overnight. The picture below literally appeared overnight. 9PM yesterday I closed up the coop. I checked on them at 7PM today. Any suggestions? Are people getting wet sand in their coops? The top layer may dry a bit but under 1/2 an inch it seems wet. Would a fan blowing on the sand help?