Lined ponds....
Lined ponds are ideal for informal schemes, as they are pliable they fit most shapes and contours, giving you the oportunity to create your own unique personal design.

Liners come in a variety of materials and prices:

Polythene...
Polythene is the cheapest material you can buy, but it will become brittle if expossed to the sun's ultra-violet radiation, so it can only be used for a temporary setup.

PVC liners....
Usually about .5mm thick these liners are very flexible and easy to mould to the shape of your pond. This is handy if you have lots of shelves and corners. They are normally UV stablised and will last atleast 30 years.

Butyl liners....
Butyl liners are made from a type of rubber and are usually about 0.75mm thick. This material stretches, which means it is highly puncture resistant and easy to fit. Many suppliers offer a life time guarantee with this type of liner.

Underlay
With all of the above mentioned liners it is advisable to use an underlay, which is basically acts a cushioning material between the liner and the surface off the excavation. If you can not afford to buy underlay, materials such as carpet, polythene, or newspaper can be used.

Calculating how much liner is needed....
A simple calculation can be used for working out the liner size required....

Max.depth + Max.depth + Lenght + overlap = total length.
Max.depth + Max.depth + Width + overlap = total width.

Installing the line pond
First mark the outside shape in the soil with a spade, a hose pipe can make a useful marker for smooth curves. Excavation can then begin to the level of the first shelf, I would recommend creating atleast one slope, this not easy access to the pond excavation, but also when the pond when the pond is finished it makes it easyer for wildlife to enter and leave the pond. Shape the shelves as you dig down, they should be atleast 30cms wide to allow the placement of planting baskets. After digging check the top level of the excavation with a spirit level.

When the exclavation is complete firm all the soil with the back of a spade, any protuding stones should be removed at this stage. Add a layer of sand over all of the excavation, damping the sand down will help it stick to the sides.

The underlay can now be place over the excavation, pushing it into all of the corners. Prior to laying the pond liner lay it out in a warm place, this will make it more flexible and easyer to handle.

Now for the best bit !
The pond liner can now be layed over the centre of the excavation, weighing down the edges with smooth stones. Fill slowly with water, adjusting the creases at they arise, the weight of the water should mould the liner into position. To minimize creasing, maintain tension by moving the stones. Once the pond is full remove the weighting stones and let the pond settle. Trimming of the outside edges can be carried out after the edging is layed down. Three examples of edging methods are illustrated below.