Stall flooring preferences vary with facilities; however, here are some general recommendations for dirt floor stalls.

First, the barn site should be elevated several feet from the surrounding area with a suitable pad. This decreases incidence of water infiltration into stalls from surrounding runoff.

Second, the sub-base of the stalls must allow for drainage: 8 inches to one foot of small rock (inch rock) is a suitable material. Above this sub-base, place about one foot of clay to clay-loam type soil.
This base will provide percolation of urine to the sub-base, yet should pack enough to provide a level floor. Bedding should be placed above the soil base.

Exceptions to this include barns that use wood flooring above a rock sub-base instead of soil and barns that use sloped concrete floors with rubber matting instead of the rock and soil base. No matter, use of bedding that absorbs moisture assists in decreasing need for percolation and drainage.