When you consider that a pond liner will have tens of thousands of pounds of pressure pushing it into the soil below, it makes sense to put some sort of cushion underneath it. Commercial underlayment material has been designed for this purpose, and – for a variety of reasons – we won't use anything else.
1. The dense, tightly woven synthetic matting protects the rubber liner from tears and punctures caused by tree roots, rocks and other sharp objects. The tight weave can also keep moles and other burrowing critters from tearing your liner. A torn liner can be a very messy, time-consuming and expensive repair!
2. Underlayment is fairly thin and quite flexible, so it molds easily to the shape of the pond, waterfall and stream. Excess underlayment folds easily without adding bulk, so there is no need to cut and piece it in the pond (pieces can shift and leave an area of liner unprotected).
3. Most ponds utilize rubber pond liner from Firestone, and using any other material – or none at all – will void the liner warranty.
4. Because the material is synthetic, it will not rot or disintegrate over time. We have fixed leaks in ponds that had old carpet pad, carpet remnants, canvas tarps and even newspaper under the liner. Over time these materials turned into clumps of rotted garbage and failed to protect the liner from sharp objects.
