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Planning a Pond - Building a Liner Pond

21st Nov 2019

Your ponds construction can begin once adequate planning has been performed and a suitable location has been found.

Mark out the Pond

Using your plan as a guide, mark out your pond’s perimeter with rope, sand, stakes or hose and then view the pond’s shape from all angles of the garden and house. When you are happy with the shape and size, the turf can be removed. At this point you can get a good feel for how the pond will look within the garden. It is worth standing back and having another good look at the pond from all possible view points, just to make sure everything is to your liking, you can remove extra patches of turf or replace turf to some areas at this stage without too much hassle.Once you are confident the best shape and size are found, digging can commence.

Dig the Pond

Any shelves dug into the pond should be 20 to 30cm deep and at least 30cm wide, this will leave a suitable space and depth for most potted marginal plants. You will probably need to dig the shelf walls at a slight angle so that they don’t collapse into the pond. If the soil is very loose you may need to set concrete blocks around the perimeter.Removed soil can be mounded to one side of the pond and used to build up a waterfall.

Check Levels

Check that your pond is level using a spirit level sat on a straight length of timber or taut length of rope reaching across the pond.If the levels are not correct then the liner will show more at one end than the other once you fill the pond with water. Block-work may have to be constructed at the lower end if the ground is sloping or uneven.

Prepare for the Liner

Once you have reached the bottom of the pond, the base should be raked and any stones, rocks, roots or debris should be removed as these could potentially penetrate the liner from underneath. If your ground is excessively stony it is usually worth laying about 5cm of sand over the bottom of the pond. Damp sand can be packed up the sides of the pond.The underlay can then be placed around the pond’s interior. You will probably have to lay the underlay as a number of patch work sheets which are cut to fit the pond. These separate sheets can be roughly stuck together with fixing tape to keep them in place. The seams don’t need to be perfect and the sheets can overlap, you must just make sure that the underlay is covering the entire interior and giving full protection before laying the pond liner.

Lay the Liner

If your choice of liner isn’t very elastic ( Polyex or PVC) the easiest way of fitting is to tuck the liner into the pond cavity before the pond is filled. This will reduce the chances of uneven strain on the liner as it the pond fills.If the liner you have chosen is elastic ( Butyl, Greenseal or Firestone) then lay the liner flat over the pond and weight the edges with rocks. Place the hose into the centre of the liner and start to fill the pond slowly, guiding your liner into the pond, adjusting the rocks and pleating any folds as it fills. Again, fill your pond slowly and any adjustments required on the liner can be carried out as the water level rises.It may be required that two liners need to be stuck together if you are adding a stream or liner based waterfall to your pond. Make sure there is plenty of overlap and adhere the liners using liner repair tape or a suitable pond-safe mastic.Joining liners together to fit a basic pond shape should be avoided as it can be difficult to ensure a water tight join across an extended length. Buying a liner which is slightly larger than required, then folding or cutting away the excess liner once it is fitted is usually a much more reliable and cost-effective option.

Let the Liner Drop

You should leave the pond full of water for a minimum of two days before any edging is added, or before the liner is trimmed down. This is due to the weight of the water, which may compact the ground under the pond and can drop the depth of the pond by up to 10cm if the ground is soft.

Pond Edging

The last stage of your construction is the addition of pond edging. There are many edging effects that can be created;

  • Stone effect liners are lengths of PVC liner coated with pebbles. These liners can be simply adhered into place around the perimeter using liner repair tape or pond-safe mastic, they are very simple to install and ideal for hiding any visible liner around the pond’s edge.
  • Grass edged ponds are created by laying grass sods over the edge of the liner and into the pond. This is a good use of the turf removed when beginning the construction of the pond. Different grasses and moisture-loving plants can be bedded into the sods, giving the pond a very natural looking finish.
  • A pebble beach is another way of giving your pond a natural look. The stones, gravel or pebbles are available from most builders’ merchants and can vary hugely in size. The bottom layer of pebbles are usually washed and cemented in place on top of the liner’s edge, once the pond has been left full of water for a few days.
  • Any cement, or limestone used must be painted with a pond sealer so that lime doesn’t leach into the pond water. Built up layers can be simply sat in place on top of the fixed base.
  • Paving the pond edge can give a more formal look. There are many varieties and sizes of paving slabs available. Matching the paving used in pathways or patios in the surrounding area can help blend the pond into the style of the garden. As with pebble beaches, any concrete must be treated with a pond sealer, this may be concrete used for bedding the slabs, or if the slabs themselves are formed from moulded concrete.