How to Build Ponds
Whether it be for watching birds cooling themselves off, or just a place of quiet contemplation, there is nothing quite as relaxing as a water feature in the garden, and high on the list comes the garden pond. There are three basic types of construction method for making garden ponds; concrete, liners or pre formed fibreglass moulds.
Concrete is a good material for making ponds in formal gardens. If properly constructed, a concrete pond can be a real asset. If incorrectly made, it will become a real headache in the garden.
Every cubic metre of water weighs one tonne. So if you are going to build a concrete pond larger than two cubic metres, you should first get advice from an engineer. Here’s how to make a small concrete pool for your garden.
How to do it
- Excavate the hole, leaving smooth sides and sharp corners. Begin construction as soon as possible to avoid the possibility of the hole collapsing.
- Install an outlet/overflow pipe at the base of the hole.
- Install a conduit pipe in the side of the hole if you need electricity cables for pumps or fountains.
- Prepare the formwork to the internal dimensions of the pond using ‘formply’ – timber that will not absorb moisture. The formwork must be tapered towards the bottom to allow for easy removal.
- Mould F62 reinforcing mesh into a ‘cage’ to support the walls and floor of the pond. Tie together the sides of the cage.
- If you are ordering concrete from a mini mix firm, order a minimum strength of 40MPA (45MPA if the pool is to hold salt water). The concrete should have a waterproofing agent added to ensure the pond will not leak.
- If you are mixing your own concrete, use a gravel:sand:cement ratio of 3:2:1. (Use a ratio of 3:1.5:1 for salt water).
- Pour the concrete into the hole, ensuring that none of the steel reinforcing is left exposed.
- ‘Rod’ the concrete walls with a steel bar to remove air pockets.
- Use a concrete float on the floor of the pond to create a fall to the outlet pipe.
- Once the concrete has set, remove the formwork.
- When the concrete has fully cured, install pipes and services, then fill the pond with water.
RUBBER LINERS FOR CONCRETE PONDS
Butyl rubber liners will prevent the problems of porosity and lime leaching that can occur with concrete ponds. Because it’s made from a black material, it is also ideal for creating a reflective pond. It is a very expensive material, but is very hard wearing and does not deteriorate in UV light.
Although concrete is often used to construct the type of ponds used for animals in zoo enclosures, most informal garden ponds are made using a plastic liner. To strike a balance between cost and durability, the most common material used for lining informal ponds is PVC vinyl. It comes in a range of colours and thicknesses, and is flexible enough to create free-form water features. It can also be repaired easily using PVC glue.
How to do it
- Set a temporary benchmark as the basis for setting other levels - final water surface, liner depth, total depth, etc.
- Measure the depth of the cuts that will be needed to have a pond of sufficient depth. Remember to allow for the depth of the bedding sand.
- Use a bobcat or traxcavator to cut out the soil to the desired depth.
- Incorporate shelves into the sides of the pond to provide habitat for different types of plant.
- Lay a sand base to prevent puncturing of the liner
- Lay out the liner in a doubled layer to improve the strength.
- Remove any air pockets from below the liner.
- In areas where crushed rock is to be used, lay geofabric to protect the liner from damage.
- Consolidate crushed rock on the areas of the liner where rocks are to be placed. This can be both above and below the finished water line, including on the shelves in the side of the pond.
- Position rocks in the crushed rock. They will create interest and can help blend the pond into the surrounding landscape.
- It is very important that the edges of the liner are above the water level and that all parts of the liner are covered, as PVC can deteriorate if exposed to UV light. It is preferable to use clay or sand to cover the liner, as loamy soil will contaminate the water.
- Fill the pond with water.
As well as creating your own shaped garden pond, there are pre-formed PVC ponds that come in a wide variety of shapes and sizes to suit your preferences.
They are easily installed.
How to do it
- Measure out the length and width of the pond and excavate the area, removing any protruding rocks and sharp objects
- Allow enough space around the pond liner for 10-15cm of sand
- Fill the base of the hole with sand and tamp down with a stick to remove air
- If the liner has a flat base, use a spirit level to level the base of your pond
- Position your pond in the hole and backfill around the sides of the pond with sand, again tamping down the sand.
- (You may have to be prepared to remove the liner and adjust the level of the sand at the base several times before you get the liner in the desired position)
- Fill with water.