Elevate Pond Liner Underlay, 270gsm
Stream and waterfall beds
Rocky or root-prone ground
Anyone protecting a liner they intend to keep
Elevate · Pond Liner Underlay
The owner's insights on liner underlay
Underlay is the cheapest part of a pond build and the one that decides whether the expensive part survives. It goes between the excavated ground and the liner, and it takes the punishment that would otherwise reach the rubber.
EPDM is puncture resistant, not puncture proof. Liners almost never fail because the rubber wore out. They fail because a sharp stone, a root or a bit of broken tile was left in the base and worked through under the weight of the water. A pond holds more than a tonne per cubic metre and it presses down on every one of those points, permanently.
At 270 gsm this is a proper geotextile, not the thin dressmaker's fleece sometimes sold for the job. Use it under every liner, on every build, including ones where the base looks clean.
How much do you need?
Same size as the liner
Work out your liner size first, then order the same area of underlay. Length + (2 × depth) + 60 cm, and the same again for width.
Overlap the joins
Underlay does not need sealing. Where two runs meet, overlap them by about 15 cm and carry on.
Two roll shapes
The 2 m x 150 m roll suits long narrow runs and streams. The 6 m x 30 m roll covers a wide pond base in fewer passes.
Do not skip the walls
Take it up the sides as well as across the base. Roots come in sideways more often than people expect.
Ordering liner at the same time?
Tell us the pond dimensions once and we will size the liner and the underlay together, so the two arrive matched.
Call todayWhat it looks like going in
Nobody photographs the middle of a pond build, so here it is drawn. The order matters: underlay before liner, then water before you trim anything.
Underlay specifications
| Material | Non-woven geotextile |
|---|---|
| Weight | 270 gsm |
| Roll sizes | 2 m x 150 m, and 6 m x 30 m |
| Use | Beneath EPDM pond liner on the base and walls of the excavation |
| Joins | Overlap approximately 15 cm. No sealing required |
| Also available | Rock Pad 500 gsm for heavy rock-set builds, and a gravel barrier for wetland and gravel beds. Ask us |
| Brand | Elevate, supplied through Aquascape Australia |
Frequently asked questions
Do I really need underlay under a pond liner?
Yes, on every build. EPDM is puncture resistant rather than puncture proof, and liners almost always fail because something sharp was left under them, not because the rubber wore out. Underlay is the cheapest component in the pond and it protects the most expensive one.
How much underlay do I need?
The same area as the liner. Work the liner size out first, using pond length plus twice the maximum depth plus 60 cm of overlap, then order the same coverage in underlay.
Can I use old carpet or sand instead?
We would not. Carpet holds water and rots, and sand washes out of the walls before the liner is even in. A 270 gsm geotextile stays put, drains, and does not break down under a permanently wet load.
Do the joins need sealing?
No. Underlay is a protective layer, not a waterproof one. Overlap adjacent runs by around 15 cm and lay the liner over the top.
Which roll should I choose?
The 2 m x 150 m roll suits streams and long narrow runs. The 6 m x 30 m roll covers a wide pond base in fewer passes with fewer overlaps. Call us with the shape and we will work it out with you.
