Installing Your Garden Pond Liner

Calculating the size of a liner

Length + (depth x 2) + 24” (60cm) = length of garden pond liner.

Width + (depth x 2) + 24” (60cm) = width of garden pond liner.


The liner required for a pond 8 feet (2.4M) long x 4 feet wide (1.2M) and 2 feet (0.6M) deep is:-

Length of liner required = 8’ + (2’ x 2) + 2’ = 14 feet

or 2.4M + (0.6M x 2) + 0.6 = 4.2M

Width of liner required = 4’ + (2’ x 2) + 2’ = 10 feet

or 1.2M + (0.6M x 2) + 0.6 = 3M

If your pond is an iregular shape use the greatest length, and width for this calculation.

This calculation will give you the bare minimum size of liner you require.

Tools and Equipment

You will need:--

  • The garden pond liner
  • Builders sand and/or underlay material
  • Wooden pegs and string line
  • Mallet or hammer, to knock in the pegs
  • Tape measure
  • Digging tools, spade, shovel, and if your ground is hard a pick can be handy
  • Hose pipe
  • Spirit level
  • Your chosen edging materials


Mark out your garden pond to the desired shape using the pegs and string line. If you need a guide, a hose pipe can be used to mark out the shape first. It’s easier to see and adjust the shape. When you are happy with the shape, use the hose as a template for the pegs and string line.

Remove the turf or top 2” (5cm) from the pond, plus 12” (30cm) for the edging to overlap the pond liner.

Excavate the pond to the depth of the planting shelf, sloping the sides at about 70 degrees. The use of a simple wooden template can help to keep the sides uniformed.

Mark the width of the planting shelf, 12” (30cm) minimum, and excavate the remainder of the pond to the required depth +2” (5cm) maintaining the 70 degree slope.

You can add further planting shelves if they are required. The planting shelves should be kept horizontal with the use of a spirit level.

For a wildlife pond the slope should be very gentle and planting shelves may not be needed.


Remove all sharp objects, stones etc from the excavated pond and lay an underlay. I recommend a pool underlay, however sand or an old carpet can also be used.

If you use sand it should be 2” (5cm) thick and will need to be damp to line the sides, and the alternative method used to fit the liner, (see below).

When you are satisfied with the underlay, spread the garden pond liner evenly over the excavation allowing it to dip slightly into the pond. Weigh down the edges with bricks or blocks.

Place the outlet of the hose pipe in the centre of the garden pond liner and slowly fill the pond with water. Adjust the tension, creases and folds until the pond is full, then leave for an hour or two to settle.

Trim the surplus liner leaving a good length over the lip of the pond. The edge of the pond can now be finished by bedding paving slabs, using sand and cement on top of the liner. Leaving an overhang will help to conceal the top edge of the liner.

Alternatively the turf can be replaced and edging stones placed around the pond. These are just two out of many ways to finish the edge of your garden pond liner. However you finish the pond edge take care not to drop cement into your pond, as it is toxic to pond life and will have to be removed and the water changed.

Alternative Method

If sand is used as an underlay and the liner is installed by the method above, the liner can drag the sand off the sides of the pond.

The alternative is, after spreading the liner evenly, loosely push into place by tucking and folding as necessary, taking care not to dislodge the sand underlay. Place bricks or blocks on the edge of the liner. Using the hose pipe fill the pond slowly whilst adjusting the tucks and folds to obtain the best fit. When filled, finish the edge of the pond as described above.

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