Installing a garden pond

Installing a garden pond


Posted 14th Jul 2015

Add interest to your outside space with our guide to installing a garden pond.
There are two options when it comes to installing a pond - you can either opt for a rigid, pre-formed plastic pond, or use a flexible plastic liner, that will allow you to design a pond that is exact size and shape you want. This guide applies to flexible liner ponds, so you can adapt the instructions to suit your project. 

 

Garden pond-step 1
1 Mark out the pond area with a hosepipe or lengh of rope, trying out different shapes and sizes. Once you've decided on a design, it's a good idea to view it from an upstairs window to see how it fits into the rest of the garden. Then, use a spade to mark the edge of the pond clearly, following the hosepipe or rope. Cut a second line beyond the pond outline to mark the outer rim of the edging. The distance between the two lines should be the width of your edging slab minus 50mm, so that the slabs overlap the edge of the pond by 50mm.

Garden pond- step 2
2 To make sure your paved edging is stable, dig a trench between the two lines before digging out the rest of the pond. The depth of the trench should be 75mm, plus the thickness of the edging slabs, plus a mortar joint of 15mm. Roughly level the trench as you go.

Garden pond- step 3
3 Cut a series of 50mm x 50mm pegs, about 300mm long, and sharpen them to a point at one end. Drive one into the middle of the trench, with the finished water level. This will be lower than ground level by the depth of the edging, which is the slab plus the 15mm mortar joint. Mark the first peg so you can recongnise it to level all the other pegs from. Position the pegs no more than a metre apart around the trench and set them with a long spirit level or laser level. 

Garden pond- step 4
4 Start to dig out the pond to the level of the marginal planning shelf, using the inside line as your guide. The shelf should be about 230mm below water level and 250mm wide. To make sure the sides are stable, dig them at a 20 degree angle rather than vertically.

Garden pond - step 5
5 Dig out the central part of the pond to the required depth, again, sloping the sides at a 20 degree angle. Make sure there are no stones sticking out of the ground. Hammer a stake into the centre of the pond and use a spirit level or laser lever to make sure it is level with the first peg. You should then double check that all the other pegs are level with the central stake.

Garden pond- step 6
6 Next, mix a fairly stiff mortar using three parts sand to one part cement and lay a line of mortar around the rim of the pond. The top of the mortar line should be level with the pegs and any edges should be rounded off to give a smooth finish. Check the level again with the central stake and leave to dry for 24 hours.

Garden pond- step 7
7 Using a plastering trowel, cover the excavated pond with a 25mm layer of damp sand. If the ground is particularly stony or there are sharp corners, use pond underlay or lengths or old carpet on top of the sand to protect the liner.

Garden pond- step 8
8 Lay the liner in the hole, smoothing out as many creases as possible - you'll need somebody to help you with this. Place some larger stones or bricks around the egde of the pond to stop the liner from slipping down. Place the end of a hosepipe in the bottom of the pond and anchor it with something heavy but not sharp. Fill the pond with water, taking care to move the bricks as the pond fills up to allow the liner to fit to th e shape if the pond.

Garden pond- step 9
9 Smooth the liner over the mortar rim and into the trench so that it covers almost half of the trench. Trim off any excess liner with a pair of scissors or sharp knife. Fill the trench with concrete, making sure you cover over the edge of the liner to anchor it in place. The concrete should be level with the mortar rim to provide a firm base on which to place the edging slabs. Leave the concrete to dry for about 24 hours.

garden pond- step 10
10 Mix mortar for laying the edging slabs by combininf four parts sharp sand to one part cement. If your pond has curved edges you will need to mark and cut each slab to fit. Use a club hammer and a bolster chisel, or an angle grinder to do this and wear heavy-duty gloves, safety googles and a dust mask. Lay the slabs on a continuous mortar bed on the concrete, so that they overlap the liner by 50mm. Allow for a 10mm mortar joint between each slab. 
Finally, before pointing the joint between the slab and liner, you'll need to empty the pond. Do this by siphoning out the water with a length of hosepipe. Clean the liner thoroughly before refilling the pond as mortar is poisonous to plants and fish.

Photos [Main image and step-by-step images B&Q's You Can Do It manual]
Feature Laura McLeish






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