Before the invention of pond liner materials, ponds were built from puddled clay. It’s clay that has had all the air pockets squeezed out of it to make a solid, immovable, watertight layer. Puddling is a labour intensive method and, although clay is a cheap material to use such ponds require constant attention as it is essential to keep the pond full to the brim so that the clay never dries out and cracks around the edge. Moisture loving plants planted around the edges provided shade to reduce the effect of sun on the exposed clay pond liner.

Nowadays the majority of ponds are built using pond liner materials. The best and most expensive material for a pond liner is Butyl or Epalyn (also known as EPDM), which will last for decades. These are rubber liners and offering the following advantages:

• resistant to damage by UV rays or frost,
• very flexible material,
• can be welded or glued together if you need a pond liner which is larger than the width of the roll,
• easy to fit and mould into the shelves and corners of a dug out pond,
• can be installed on any soil type, although the laying of a protective pond underlay between ground and liner is always adviced.

A less costly option is PVC pond liners, which is not as durable as Epalyn or Butyl but will last about 15 years if looked after.

Rubber and PVC pond liners can be used to line ponds built in any soil type provided that the surface has been cleared or rocks and stones which may damage the liner. Whereas, a puddled clay pond needs a firm base, so you cannot use this method on recently disturbed land, or too near the edge of a slope where soil may creep downwards or subside. Gravelly, silty and peaty soils are affected by ground water and move therefore unadvisable for the build of puddled ponds. The puddle clay will also move, resulting in cracks and leaks.

While puddled clay ponds are still built today, the majority of ponds are constructed using pond liners because they are less labour intensive to build, a smaller hole is required as the thickness of a pond liner is a fraction of the thickness required for clay, which needs to be at least 20cm thick and a rubber liner is not likely to be affected by UV rays should it be exposed due to the drop in water level.