I just moved my 5 week old hens into their coop and run over the weekend. The coop is raised with a wood floor so I use pine shavings and its nice and dry and fine. The covered run has a concrete floor and the first night and day it rained and I did not have gutters so the rain dripped down the hardware cloth and the pine shavings got wet. I cleaned it all out because no matter how much I sifted and mixed it throughout the following days, it would not dry out. I had gutters installed today. I hesitate to add pine shavings back in and have been thinking about adding a layer of pebbles and then construction sand over top. I'm in Maryland and we've had an unusual amount of rain over the past year so I'm anticipating the concrete retaining some dampness. Even though the gutters will solve the "flooding" I had, I know I will always have some moisture on the floor after rain so my hope is with sand it will offer the fastest drying time out of all the bedding options. Does anyone have any experience with using sand or other bedding on a concrete run? Thanks!