Building a Garden Pond and Choosing the Right Materials
Ponds need to be watertight and, within reason, it does not matter how this is achieved. When it comes to the material used to form the base and sides of your pond, there are three main options:
1. Preformed rigid glass fibre or plastic liners
2. Flexible polythene, PVC and butyl liners
Advantages and disadvantages
As always in gardening, things are never straightforward. Whereas a flexible liner is the ideal solution for one gardener, another will prefer the concrete option. The following three areas will need to be considered before you make your choice.
The question of comparative costs is probably the first thing you would want to investigate. However, the price of liner for a pond of a given size is very similar, whether you opt for the pre-formed type or flexible sheeting.
The cost of liners will vary according to where you buy them. For example, a liner bought from a high-quality garden centre in an ‘up market’ neighbourhood will, almost certainly, cost more than the same product if bought from a town market or via a mail order supplier.
Both flexible and pre-formed pond liners come in various grades of thickness, and this, too, complicates any price comparison.
In reality, after all variables are taken into account, there is little difference in cost between the two types of liner.
Ease of Installation
In its simplest form, making a pond with a flexible liner involves digging a hole, placing the liner into it, and then filling it with water. Pond making could not be simpler.
However, without attention paid to trimming, folding, tucking and, possibly, glueing, the end result may be less than satisfactory.
On the other hand, a pre-formed pond freshly delivered from the retailer is ready to be sunk into a hole in its chosen place. However, the hole needs to be dug to exactly the right shape and size, and kept perfectly level. This is easier said than done.
Both types of liner need underlay or soft backing to prevent large stones from penetrating the material once the pond has been filled with water. Indeed, the quality of the, and the ease with which you can create a hole in it, may be the single determining factor.
One might conclude that a simple, shaped pre-formed liner would be better for a small square or round formal pond, and that a flexible liner is better if you want a large, informal pond. Ultimately, however, the desired shape of pond will have the main bearing on the liner that you select, and you may find that the conditions which prevail in your own garden are a particular consideration.
Ease of Maintenance
On-going maintenance is usually of concern to pond owners who are planning to live with the same garden for at least 10 years.
Ponds made of concrete do tend to be the most labour-intensive in terms of on-going maintenance. Ground movement can create cracks, and old concrete can become brittle. Repairing kits and sealants are expensive.
Cheap-grade flexible liners, when exposed to sunlight, will degrade in time. Liners w
ith a guarantee of 10 years or more should be sought (even better are those with a 35 year guarantee).
Pre-formed glass fibre or moulded plastic ponds are extremely rigid, and usually thick enough to repel knocks and grazes. However, a badly placed boulder set underneath the filled pond can do more damage to a pre-formed liner than to a flexible one.