Garden Ponds - Building a Garden Pond

supplied by Wickes.co.uk ©2008 All rights reserved.

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It's surprisingly easy to create a pond in even the smallest garden, thanks to the development of long-life flexible liners. All you have to do is dig a hole in the ground, lay the liner in place over an underlay and fill it with water, ready to receive plants and fish. Add a small submersible pump, a length of hose and a second section of liner and you can easily create a fountain and waterfall too.

The Wickes pond liners are made from black PVC, which gives a greater impression of depth than other colours and is more resistant to degradation by ultra-violet light.

 

1. Decide on the Location

Try to choose a position where you can admire the pond from your favourite sitting-out position. The ideal pond site is in a sunny spot, sheltered from cold northerly winds and well away from trees that shed their leaves. Too much shade will encourage algal growth, while falling leaves will soon clog up the pond in autumn. In fact, it's best to avoid sites near any large trees, since their roots could spread and damage the liner in the future.

There's no reason why you should not build your pond on a sloping site, so long as you are prepared either to cut into the slope or to build a retaining wall or bank on the downhill side of the pond. Such a site can also be a natural one for a waterfall.

The only thing that might cause trouble is if you live in a very marshy area, or one with a high water table (the level of natural underground water). In either of these cases, the pond liner may tend to float upwards due to pressure of water from below. You can check this by digging a small hole to the required depth of your pond and noting whether water accumulates or not. If it does to any noticeable extent the site is not suitable for a pond.

 

2. Decide on the Shape

The Wickes pond liners can be used to create a formal or informal shape. The formal will be a square, rectangle or circle, while the latter can be any shape you like within reason: it's best to avoid curves and inlets that are too 'sharp'. The simplest way of establishing the shape and size you want is to lay garden hose or rope out on the pond site, and to view it from various positions. It's often helpful to look at it from an upstairs window as well as from ground level. Keep a check on the size since it is easy to plan out a pond which is too big for the liner, and liners are not intended to be joined.

 

3. Decide on the Type

You can create a pond either by sinking a preformed rigid plastic or glass fibre shell in the ground, or by lining the excavation with a flexible liner. The latter is the more popular choice for several reasons: it's easier to transport since it comes folded in a box; it's easier to install, it also allows you complete freedom of choice as far as the pond shape and depth is concerned, and this is the type that Wickes sell. The thickness of the liner ensures long life so long as it is properly installed, it can be repaired easily with patches if it is punctured accidentally. Also, the fact that it follows the contours of the ground results in a much more natural-looking pond.

NOTE: You can use flexible liners for above ground formal ponds with raised brick or stone walls too.

 

4. Think About Extra Features

Decide at this stage whether you want to incorporate extra features such as a waterfall, a fountain, garden lighting, and the like in your pond construction. Apart from the relaxing sound moving water creates, the movement helps to aerate the water too. A fountain brings a three-dimensional effect to your pond, and can look sensational at night coupled with outdoor lights around the pond.

Most ponds will attract a variety of animals found in the garden. Therefore think about providing for them too.

If you have Hedgehogs in your garden, think about providing a sloping beach for them to climb up if they fall in, or use plants to help them escape.

 

5. Plan a Power Supply

If you're using a pump to circulate water to a fountain or waterfall, and perhaps using outdoor lights, you'll need a power supply to the vicinity of the pond. This must be a permanent supply run underground from the house using toughened cable, not a trailing flex plugged into a socket outlet. For complete safety, the circuit to the pond should be protected by a 30mA residual current device (RCD). - see CUSTOMER CARE and also step 12.

All electrical work must conform to BS 7671 the current IEE Wiring Regulations, and Part P of Building Regulations. You are advised to check with your local authority's Building Control Department, or an Authorised Competent Person, before starting. If in any doubt about electrical work, contact a qualified electrician.

 

6. Think About Soil Disposal

Digging big holes creates a surprisingly large amount of spoil, so unless you can disperse it elsewhere in the garden or you are planning to use it as the base for a rockery or other raised feature, you will have to order a skip and have it taken away.

 

Customer Care

There are two points to remember as far as safety is concerned: electrics and children.

Electricity used out of doors can be dangerous, so if you need a power supply for a pump or outdoor lights, ensure that it is provided by a permanent circuit run from a spare fuseway in your consumer unit (or from an additional consumer unit mounted alongside if you have no spare fuseway).

You are not permitted to run a spur from an existing house power circuit. The new circuit should be run in special toughened outdoor cable, buried in a trench at least 500mm deep running from the house to the pond. At the pond end the cable is linked to the pump flex inside a special weatherproof junction box. At the house end it should be wired to a piece of safety equipment called a residual current device, which will cut off the supply to the circuit in the event of an electrical fault. If you are in any doubt about your ability to carry out electrical work, call in a qualified electrician to do the job for you. You will also need professional help if a new consumer unit is required.

WARNING: If you have small children in the family, the main risk is of them falling into the pond. You can guard against this in several ways. One is to erect a low fence around the pond, or to build a raised pond rather than a ground-level one. The alternative is to create a water feature that has no deep water - perhaps as a waterfall linking a small header pond at the top to a fountain that discharges into a shallow basin filled with pebbles at the bottom. With this arrangement however, you won't be able to keep fish.

 

Useful Tools for Hire

If you are planning a large pond or you have particularly rocky subsoil, it may be worthwhile hiring a powered breaker or even a mini excavator to make the digging easier. A builder's barrow is worth hiring for moving spoil if you have only a flimsy gardener's barrow. And if you're disposing of a lot of soil, a power barrow - a motorised wheelbarrow - will make light work of moving it from pond to skip. A large angle grinder will be necessary if you intend to cut paving slabs to fit around the perimeter of the pond.

See Good Idea Leaflet 14 - Paving and Walling.

 

Work Sequence

 

1. Decide on the Site & Mark Out the Shape

Take your time in deciding what shape of pond you want, adjusting the hose position and viewing the shape from an upstairs window to get a better idea of how its shape and proportions fit in with the garden as a whole. If you are having an informal shape, avoid sharp curves; gentle sweeps look more natural. FIG. 1 shows a few possible layouts.

Don't forget that you need a minimum surface area of about 3m2 (32sq.ft) if you expect your pond to become selfsupporting as far as plant and aquatic life is concerned; smaller ponds may not contain enough oxygen and so tend to stagnate.

 

2. Cut & Remove Turf

When you're happy with the shape and size, cut round the perimeter with a spade or lawn edger. Then cut across the pond area in parallel lines about 300mm apart, and lift the resulting strips of turf. If you want to reuse them elsewhere, roll the strips up carefully, stack them out of the way and keep the stack moist until you are ready to re-lay them. If you don't want them, offer them to neighbours, turn them into compost or dispose of them in your skip.

 

3. Excavate to Marginal Shelf Level

Start excavating the pond area down to the marginal shelf level, saving good topsoil for use elsewhere in the garden. For the deluxe pond, dig down to a depth of about 320mm (121/2") below ground level which will give you an eventual water depth of about 230mm (9"). Slope the sides at an angle of about 45°, clearing any roots and sharp stones as you work, then check that the base of the excavation is roughly level using your spirit level set on a timber straightedge. See FIG. 2.

 

4. Excavate the Deep End

Next, mark out the area that will form the 'deep end' of the pond. This is normally the central area, but it is not essential to have a marginal shelf all the way round.

See FIG. 3 shows some layout possibilities.

Excavate the main section to a depth of between 550 and 700mm (21 to 27") below ground (lawn) level; the latter is better, since it guarantees that the pond cannot freeze solid in winter. Your eventual water depth in this area will be about 450 to 600mm (18 to 24"). As you work, try not to break down the edges of the marginal shelf, and do not make the sides of the deep end too steep - an angle of about 45° is about right here too. Again, remove roots and sharp stones as you find them, packing soil firmly into the resulting holes.

 

5. Line the Hole with Sand

Double-check that there are no stones left which could puncture the liner, especially on the edges of the marginal shelf or the slopes down into the deep end. Then line the excavation with a maximum 25mm (1") thick layer of damp building sand, patting it into place on the slopes and firming it down on the bottom and the marginal shelves. This will help to cushion the liner and prevent any rogue stones from penetrating it once it is filled. It is well worth covering the sand with an underlay to further protect the liner in the event of the sand being washed away. An ideal material is our 620-801 Acoustic Underlay normally used under our Laminated Flooring and available in 15 x 1 metre rolls.

 

6. Remove the Edging Turf

With the excavation complete, the next step is to remove turf round the pond to allow for the edging stones. Use an angle grinder to cut slabs to fit if necessary but make sure that you are wearing a nose and mouth mask and goggles for protection. Lay the stones in place so they overlap the pond edge by about 50mm (2"), and mark their outer edges on the grass with your spade. Then lift the slabs aside, cut and lift the turf and remove the topsoil to a depth of about 65mm (21/2") - enough to allow the slabs to be bedded on mortar once the pond is filled. See FIG. 4. Check that this perimeter strip is perfectly level all round; if it is not, parts of the liner will be exposed above the water level, and will begin to deteriorate due to exposure to sunlight.

 

7. Position the Liner

Drape the liner over the excavation without disturbing the sand or any underlay, aiming for an even overlap all round. On concave curves, pleat and fold it neatly. Don't make it fit the pond contours precisely at this stage though. It will look better if it is allowed to stretch slightly as it is filled, since this will help to pull out many of the creases. When you're happy with its positioning, anchor its perimeter with bricks or stones. See FIG. 5.

 

8. Position the Waterfall Liner

If you are having a waterfall, now is the time to install a liner - in an existing rockery, or on a new earth bank. Use an offcut from the main liner. Form the top pool first with a depth of about 120mm (41/2"), then create a channel for the liner down to the pool. One of the easiest ways of doing this is to lay roof ridge tiles upside down in the channel to form the cascade, and then to position the liner over them and tuck the excess material underneath. See FIG. 6.

Alternatively, lay the liner directly in the channel, anchor its edges with stones, and use pieces of paving slab underneath it to help form steps over which the flow can cascade. Position another slab at the point where the waterfall will discharge into the pond, to ensure that the water does not 'miss' the pond edge. Then bury a length of 25mm (1") hose running from the pump position in the deep end of the pond, over the pond edge and up the slope to the top of the waterfall, covering it with pieces of slate, tile or similar so it is not squashed when buried or pierced by gardening tools.

 

9. Start Filling the Pond

Start filling the liner with water from a garden hose. As it fills, neaten folds as necessary and ease off the perimeter bricks to allow the liner to bed against the contours of the excavation. As the water level nears the top edge of the liner, check to see how level the pond perimeter is and scrape away soil to get rid of any high spots or make up low spots with well compacted sand. Fill the liner to within 25mm (1") of the top.

 

10. Trim the Liner

Trim off excess liner all the way round the pond with a sharp knife, leaving an overlap of about 230mm (9") which will be concealed by the edging stones.

See FIG. 7. If you are planning to turf-up to the pond edge at any point, cut slits in the overlap so the grass roots can grow through them into the soil below.

 

11. Lay Paving Stones

Tidy up the site, and lay the edging stones round the pond on a 25mm (1") thick mortar bed. It is not safe to bed them on sand, as you would on a patio, since someone standing on the edge might tilt the slab and be thrown into the water. Check that the slabs are level, and point between them. If you are having a pump and waterfall, conceal the hose to the waterfall by positioning it between two slabs, and set a short length of copper pipe or plastic conduit beneath the slabs to allow the pump flex to be passed through safely and unobtrusively.

 

12. Run In & Connect the Water Supply

Run in the power supply, using 1.5mm2 toughened twin and earth cable buried at least 500mm (20") underground between the house and the pond site. At the pond end, pass the pump flex through the pipe or conduit under the perimeter paving and connect it to the toughened cable within a weatherproof junction box; then form an above-ground chamber for the box which you can later conceal with rocks or shrubs. The simplest solution is to set the box on a brick or block and cover it with a ridge tile; alternatively, mount it on a low timber post and shield it from the weather by making a small canopy for it from exterior quality plywood or fencing offcuts.

Indoors, run 1.0mm2 twin and earth cable to the consumer unit position and connect to either a spare fuseway or miniature circuit breaker (MCB) in a new consumer unit mounted nearby. You must call a qualified electrician or your local electricity company to connect this unit to your mains supply. Fit a 6-amp fuse in the fuseway, or use a 6-amp MCB, and label it 'POND SUPPLY'. See FIG. 8 for full wiring details.

Now connect the waterfall hose to the pump outlet, and set the pump in the pond on bricks or pieces of paving slab so the fountain jet is just above water level. Switch on the power by turning the residual current device to ON, so you can test the system. Adjust the water flow as necessary using the flow adjuster. Do not restrict the flow too much as this can damage the pump over a period of time.

 

 

13. Stock the Pond

Complete the pond installation by adding marginal, deep-water and oxygenating plants. Remember that your pond will only support plant and aquatic life if the surface area is about 3m2 (32sq.ft) or larger. Don't worry if the water goes green initially; it will clear as the plants establish themselves. Wait a few weeks before stocking the pond with fish.

 

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