I’m wanting to make a round pen with sand to be able to use when my regular arena ground is slick (it’s heavy soil). What size round pens do like and what depth of sand do you recommend? What do you recommend I do to the ground before adding sand. The area I’m considering putting it in is currently a grass area but nice and flat. Should I pre work it or can I add sand on top? Im worried if I pre work it and then work the sand in my sand will take on the heavy clay and be useless. All advice appreciated. — ?looking for recommendations.

Bump

The area of the country you are in and the moisture and rockiness of the soil determines what goes underneath.  The base needs to drain. . If you have ground that holds water for DAYZZZZ  after a rain then you may need to put a base layer.  If your soil is already loamy and drains well then adding sand on top makes sense.  the depth of the sand depends on your discipline.  Im assuming you are exercising barrel horses so I would recommend about 3-5 inches of sand.  deeper than that is more for cutters with hard stopping and they typically prefer around 6 inches.  Also you need to make sure you have something around the base of the round pen so all the expensive sand that you hauled in doesnt just run out.  one clever idea I have seen is someone cut stall mats in strips about 2 feet wide.  they attached them vertically to the base of the panel with some screws looped over the rung of the panel and they kept the sand in.  Also if a young horse got fresh and kicked then the stall mat is soft.  

We live where it is very rocky and the soil does NOT drain and it turns into gumbo, sticky mud when it gets wet.  its the absolute worst.  When I put in the arena I wish I had made a thick rocky base then covered it with some sort of landscape paper to keep the rocks down and the weeds from growing then put sand on top.  Instead I asked at least a dozen "dirt guys" around here how to do it and they all said to put red house foundation dirt down and pack it and it would stay hard then put sand on top and the rain would drain through the sand and off the top of the foundation.  It kind of works but I feel like had I done it the other way it wouldve drained faster.  Of course its way too late for me to change it.  I am going to scoop out some of my run outs from the barn and try the rock trick at some point and see how it works.  Im so tired of the mud.

I would be interested to see what other folks have to say.  These are just my thoughts.