You have several choices when it comes to selecting the proper materials for building a garden pond. The most popular and versatile waterproofing material is a flexible pond liner. It allows you to design the pond to your requirements and personal taste and gives you the option of completing the entire project by yourself without the need for a knowledgeable landscape contractor.
Flexible pond liners are made from PVC, EPDM, HDPE, BUTYL, etc. and range in thicknesses from 15 to 60 mil. The most popular and easy-to-work-with thickness is 35 to 45 mils. For small-scale projects on a limited budget you may be able to get away with thinner liners but, because they are more susceptible to tearing and puncturing, you have to be more careful.
Make sure that the liner you purchase is non-toxic. This is imperative for growing waterplants and keeping fish in your pond. Do some homework and select a pond liner with a proven track record and a good manufacturer's warranty. Look for things like UV-resistance and non-toxicity, as well as resistance to extreme temperatures.
These features become extremely significant when the material cost and labour for the liner installation are put in relation to the overall cost of the entire project. Liner plus installation cost represent only a fraction of the investment in the completed project. However, if the liner has to be replaced due to a product failure, the above cost relation reverses. The replacement of a pond liner necessitates the removal of all components, such as edging materials, plants, fish, pumps and fountain equipment, and most importantly, a very smelly liner. For that reason alone it becomes imperative to select a product with a proven track record of trouble-free performance.
Do not use old swimming pool liners. They are bad news. Due to their color they look artificial which you may be able to live with but, over the years, they may have absorbed quite a bit of chlorine and other pool chemicals which could leach back into your pond and destroy all life within it.
Once you have selected a suitable pond liner you have to decide whether you can use a standard size liner or whether you have to get one custom made to fit your pond's particular size and shape. Most companies offer several choices of standard sizes which are usually a little cheaper than a custom size and are also more readily available.
To figure out exactly what size of liner you will require you can either take the measurements off your plan or wait until you have the excavation completed.
Use the following formula to calculate your liner requirements from a plan:
Length of liner required = Max. length of pond + (2 x max. depth of pond) + min. 2 feet (min. 60 cm) overlap
Width of liner required = Max. width of pond + (2 x max. depth of pond) + min. 2 feet (min. 60 cm) overlap
If you are measuring off a completed excavation use a flexible measuring tape or a rope that completely conforms to the contours of the excavation. To determine the full length of liner required run the tape or rope down into the pond, exactly following the contours of the excavation, across all the ledges, to the bottom of the pond, and back out the other side. Then add at least 2 feet or 60 cm (min. 1 foot or 30 cm per side) to allow for sufficient liner overlap outside of the pond. Use the same method to determine the width of the liner. Be sure to measure across the maximum length and width and at right angles to each other.
Another very popular choice are pre-formed ponds. These are heavy-duty pools, usually made from high-density polyethylene, glassfibre reinforced polyester, fiberglass, etc. They stand up very well to the elements, are hard to destroy and come with a long-term manufacturer's warranty. The installation can easily be accomplished by the average home owner.
Pre-formed ponds are, however, not nearly as versatile as flexible pond liners. Most of them are relatively small and usually have only one, maybe two, planting ledges. You have no input into the design, shape and depth and are limited to whatever is commercially available.
Another factor is cost. You will find that a flexible pond liner that covers the same area as the pre-formed pond is usually quite a bit cheaper.
The other two materials suitable for waterproofing a pond are clay and concrete. Most of us would require the help of a specialized contractor to apply any of the above, and they are therefore not the materials of choice for the do-it-yourselfer.
In addition to a pond liner or pre-formed pond you will also need some sand and/or a non-rotting polyester felt to act as a cushion and protection layer between the liner and the soil underneath it. When using heavy boulders as edging materials or when placing heavy objects within the pond we recommend using heavy-duty rubber mats as a protection layer between the boulders and the pond liner. This is explained in more detail in the Installation section.
Unless you plant them in a bog garden, water plants are best planted in pots. This facilitates future changes and moving them to other locations within the pond, as well as moving them to a deeper spot or indoors for overwintering. Contact a waterplant specialist or grower for advice on plants that thrive in your particular area and climate zone.
You also need the proper edging materials to complement your pond's appearance. Popular choices are river rocks, pebbles, patio slabs, irregular rocks and boulders, etc. Avoid anything with sharp or rough edges that could puncture the liner or provide a suitable protection layer of polyester felt or rubber mats. You can find more information on this subject in the Edge Design and Installation sections.
You might also consider adding a submersible fountain pump with a spraying or bubbling fountain head, a pond filter or underwater lights.