SAND "Contractor Type" > Some Contractor sand is almost play sand, a fine grit many times rust in color or grey. This is not the suggested Sand. Look for the contractor sand that have various grit of many sizes (tiny to medium pebbles) which is almost gravel from the bottom of a stream bed. Some of the particles digested by the hens are useful for digestion and larger grit or pebbles simply act as a loose floor base material. Eventually a large percentage of the sand mix will be absorbed into the soil and disappear eventually.
Naturally, hard clay will retain water at its surface, so I prepare sufficient top soil and contractor sand mixed together to make a 5 to 6 inch floor covering in my coop. Add the hay or straw over the top of the floor adds another benefit to moisture control. Include the Diatomaceous Earth to control mites, etc.