Dear Cody,

With both an indoor and outdoor arena, site selection is important. A good-level site should be selected and built up high enough to facilitate drainage in both cases. Arenas and training areas can be of any configuration you desire. However, you need to keep wind direction and topography of the land in mind before laying out your horse barn and arena. In addition, consider how the horse and rider will enter and leave the arena during all riding times and seasons to plan for maximum safety and convenience.

The process for developing the arena floor is similar for both an indoor and outdoor arena. Careful excavation, selecting quality base and footing material, and correctly installing the materials will ensure an arena's long-term success. The arena floor is composed of three layers:

Sub-Base – the layer of soil directly below the topsoil.
Base – 4 – 6 inches of added material (usually ground limestone) over the sub-base that defines the arena floor.  This layer is often packed at a slight slope to allow for drainage of an outdoor arena.  
Footing (surface) – 2 – 3 inches of surface material that comes into contact with the horse’s hooves.

The sub-base and base can be engineered to aid drainage in an outdoor arena. Various riding surface materials are available, with 2NS sand being one of the most cost-effective and common materials used for outdoor arenas. 

There are some great resources for developing a riding arena that will discuss the many footing options and go into detail about installing a good base.  Below are some resources that may be helpful: 

Finally, we have a short course through MSU Extension's My Horse Univesity platform, which has a unit dedicated to developing riding arenas.  It is currently FREE, but we will be moving into a fee-based course very soon.  

https://www.myhorseuniversity.com/summer-horse-care-101

Feel free to reach out to me directly if you want to discuss your riding arena further at <personal data hidden>.