The base of your arena is arguably the most important part of the project. Indoor arenas are slightly simpler than outdoor arenas in that they generally do not have to cope with rain. This means that they can be dead level. Outdoor arenas are typically either sloping or domed to allow water to flow off the arena.

The current common practice for constructing arenas is based on road making. The process consists of:
  • Levelling the site
  • Putting down layers of coarse rock
  • Putting down layers of finer rock
  • Adding the surface
The size of the rock and thickness of layers is critical. The correct sizing will restrict or prevent the movement of the rocks between the layers. The subsurface is compacted (rolled with watering) to consolidate it. Compacting the subsurface is critical to ensure that there is no movement in the sub surface. Water is essential to the process as without it the rock will not compact. Too little water will result in inadequate compacting and too much water will result in the larger stones rising to the surface and the smaller particles sinking. Do not allow this process to be rushed as fixing it is very expensive and difficult.

It is worthwhile to schedule a fair bit of time (in the order of a week) between the completion of compacting and the first trucks arriving on site to commence construction. This time is to allow the base to dry out and ensure it is solid. Alternatively, you can finish the levelling and compacting of the surface after the shed is constructed. Be aware that you can't roll too close to the footings.

Drainage


Drainage is another critical aspect of an arena. Good arenas are easily destroyed by water seeping under the edges. So it is essential that the arena be higher than the surrounding ground and that there are adequate drains to take surface water away from the arena.

When things go wrong


Unfortunately our base got too wet and some of the larger stones rose into the smaller stone layers. The fix was to add an additional layer of very fine stone (less than 5mm) optionally with a bituminous emulsion to bind the layer together. This creates an impervious layer that keeps the large stones down. The surface of this layer needs to be protected from direct contact with horses hooves to prevent wearing.

Dust


Dust is a continuous problem with indoor arenas in particular; we applied a layer of Dustex (lignosulphonate) from Dustex Australia (http://www.dustex.com.au/) to reduce the amount of dust that comes up from the base and through the surface. The Dustex also aided in repairing the base when a beam was dropped on to it as we could recompact the disrupted area and effectively glue the base back in.