There are several ways to line a pond: concrete; puddled clay; rigid liner; flexible liner.
Without a liner, a pond will not retain water, unless it is being fed from an external source. Using this method can create problems, as the water must be silt-free to avoid the pond silting up.
Concrete is prone to cracking and difficult to repair; puddled clay can be difficult to obtain, and takes a lot of work to get right; rigid liners are rarely suitable, and can be awkward to install; flexible liners are easy to handle, and shape themselves to the contours of your hole.
There are several different types of flexible liner, including polyethylene, pvc, Firestone rubber and Butyl. We always recommend Butyl or Firestone rubber as the best choice for larger ponds, where the liner may be damaged, or where the longest possible life is required. Smaller ponds can be lined with polyethylene or pvc liners, which often have a shorter lifespan than butyl, are more prone to tearing, cannot easily be repaired, but are much cheaper. Note that we are able to offer the manufacturer’s Lifetime Guarantee on our Butyl, Firestone Rubber, and PVC pond liners.
Wherever possible, it is wise to obtain the best quality liner, as there is nothing worse than having to re-do a pond which has developed a leak, and cannot be repaired. Therefore, Butyl or Firestone rubber are the recommended choices. There are two thicknesses of Butyl liner generally available: 0.75mm & 1.0mm. Unless constructing a large lake, the 0.75mm liner should be more than adequate. Firestone rubber is available in 1.0mm thickness. Pond liners should ideally be underlain with a cushion underlay, which will give maximum protection. Beneath this should be a layer of sand, to provide additional protection against stones and roots, which may work their way up through the soil and puncture the liner. You could also place cushion underlay on top of the liner for added protection, and to aid retention of soil, which might otherwise slide off.