How to Get Your Pond Liner Size Just Right

So, you’ve dug a wide and deep enough hole in your garden and you’re about to take the plunge (metaphorically, of course) and order your pond liners. Before you do, it is worthwhile understanding a few important rules that will help to calculate the appropriatemore pond liner size for your garden dug-out.

How to order the correct pond liner size

• Don’t try to predict the size of your hole. Wait until it’s been dug, and you are happy with the size, shape, depth and design before going ahead measuring it.
• Take accurate measurements. If your pond liner ends up being too small you will either have to shovel the soil back into your hole or order a new pond liner and protective underlay.
• Allow for at least 30cms overlap onto the pond perimeter.
• If you have chosen EPDM (Epalyn) or butyl rubber pond liner, there is, in theory, no limit to the width of the material as good suppliers will weld sheets together to achieve the size you require. In the case of cheaper PVC linings, these are typically available up to 8m in width.

Pond liner size calculation

The first step when measuring your pool is to find the deepest point and measure the depth. This is easiest done by placing a board across the hole above the measurement point and measuring up to that. Now measure the length and width and make the following calculation: the length + twice the depth + 60cms = the total length of your lining the width + twice the depth + 60cms = the total width of your lining Doubling the depth accounts for lining the two walls and the 60cms allows an overlap of 30cms at each side or end. So, if your pond is 3m long by 2m wide with a depth of 1.5m, the pond liner size needed would be 6.6m x 5.6m. 

The string method

If maths is not your thing, an alternative is to take a length of string and place it at one end of your pond where the liner would start (remember the 30cms overlap) and then take the string down into the bottom of the pond, across and up the other side, making sure it is touching the walls and bottom all the way. Then mark or cut the string where your lining would finish on the other side and measure the string. Repeat the exercise for the other dimension. Don’t worry if your hole is not rectangular. These methods will work for oval or kidney-shaped ponds – just make sure that you take the maximum length and maximum width. If your pond is a complex shape – like an L or a U, then just divide it up into two or three chunks each of which can be measured using the methods discussed.

Remember though, that you will only need to allow one depth measurement, not two, for the adjoining dimensions as the pond liner will be joined on the bottom and there is no wall to account for. Your supplier will be able to advise on the amount of underlay required for your pond liner size . It is worth adding on some extra to allow for protecting your pond liner around the perimeter where it will be fixed under soil, slabs or rocks and to protect any shallow areas of the pond you intend to plant.

Autumn is a good time to dig a hole for your pond and prepare the surrounding garden ready for planting in the spring. The ground is damp and a lot easier to dig-up than during dry summer spells or winter when the ground is frozen solid. It is not advisable to introduce fish or plants until the spring. If you are planning to build a pond and need help with ordering a pond liner, protective underlay or pond pump contact us at Liners Online and we will gladly offer assistance.