A riding arena is only ever as good as what sits underneath it. Get the base right and the surface will ride well for twenty years; get it wrong and you will be pulling it up within two. Here is how a proper arena base is built, based on the ground conditions we actually deal with around Chorley and the wider Lancashire area.
Most of the ground around Chorley sits on heavy clay, which holds water and moves with the seasons. That means drainage has to be designed in from day one, not added later when puddles appear. Before any digging, walk the site after heavy rain and note where water sits, because that tells you more than any brochure will.
A standard 20m x 40m arena needs a level or gently graded platform. On sloping paddocks that usually means a cut and fill exercise, digging into the high side and building up the low side in compacted layers. Fill that is simply tipped and not compacted in layers will settle unevenly and crack the finished surface.
All topsoil and organic material must come off the footprint, because anything organic will rot, settle and pump mud up through your stone. Excavation typically runs 250mm to 400mm deep depending on how firm the subsoil is once you reach it.
On clay, a herringbone or lateral drainage system is laid in trenches across the formation, using perforated pipe bedded in clean stone, falling to a soakaway, ditch or watercourse. Drain runs are usually spaced 3m to 5m apart. If your site outfalls to a watercourse, check whether consent is needed before connecting in. Skipping drainage on Lancashire clay is the single most common reason arenas fail.
The sub-base is where the money should go. A geotextile membrane goes down first over the formation to stop the clay migrating up into the stone. On top of that, 150mm to 250mm of clean crushed stone is laid and compacted with a vibrating roller. Many builds use a clean limestone or granite in the 40mm to 63mm range for the main layer, because clean stone lets water pass straight through to the drains, whereas ordinary MOT Type 1 with fines can seal up and hold water.
Above the main stone layer comes a blinding layer of smaller stone, around 25mm to 40mm thick, rolled to a tight, even finish with a slight camber or fall of roughly 1 in 100 so surface water always has somewhere to go. Some builds add a second membrane here to keep the riding surface separate from the stone. Only then does the riding surface go on, typically 100mm to 150mm of silica sand, often with a fibre or rubber additive, depending on the disciplines you ride.
For a full size 20m x 40m arena in this part of Lancashire, groundworks and base construction commonly land somewhere between £25,000 and £50,000 including the surface, though it depends heavily on access, how much muck needs carting away, drainage complexity and your choice of surface. Tight access that rules out eight wheeler wagons pushes haulage costs up quickly.
Timewise, expect one to three weeks on site for the groundworks in reasonable weather. Autumn and winter builds on clay are possible but slower, and compaction is far better achieved in drier months. Remember that most arenas need planning permission, and fencing, gates and lighting sit on top of the figures above.
In almost all cases yes, because an arena is an engineering operation and a change of use of agricultural land. Speak to Chorley Council or your local planning authority before spending anything on materials.
You can do some enabling work, but the excavation, drainage and compaction need plant and experience to get right. A poorly compacted base usually costs more to dig up and redo than it would have cost to build properly once.
Most builds total 300mm to 450mm from formation to finished surface, made up of roughly 150mm to 250mm of compacted clean stone, a blinding layer, and 100mm to 150mm of riding surface. Softer ground needs the deeper end of those ranges.