Okay so, our Easter holiday chicken run project is well underway! Our next step is deciding on flooring for the run. Background: We live in the UK, so expect quite a bit of rain. Our run will be 1/4 to 1/2 covered with a solid roof. The run is 3m x 2m. And also has a raised chicken coop. It will house 3-5 Silkie Bantams (depending on how the hatching goes) and they will also be allowed to free-range the garden when we come home in the evening. Currently the ground is mud. We are going to level it out. Secure wire mesh across the whole floor (added security from the local fox) and then add a membrane/ weed matting across the whole floor to suppress the weeds and mud coming through. The Question: Now we are just deciding on substrate. In my head I have sand or gravel. What are your experiences, advice and thoughts on these choices?