Pond Liner Underlay: All Guides
Quick answer: Lay a geotextile underlay beneath every pond liner to protect it from stones, roots and ground movement. 200gsm suits most garden ponds. Order underlay in the same size as the liner and overlap any joins by at least 300mm.
- Underlay goes beneath the liner, never on top as the main layer
- 200gsm needle-punched polypropylene, about 2mm thick
- Order the same size as the liner
- Overlap joins by at least 300mm; no adhesive needed
- The 40-year HDPE liner includes underlay; the 25-year HDPE liner does not
Last reviewed: 3 October 2026 · Reviewed by the PondLinersco.co.uk team
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All guides (3)
- Do You Need Pond Liner Underlay? UK Expert Guide 2025 — Yes. Geotextile underlay should go under almost every pond liner to protect it from stones, roots and sharp objects that work up through the soil over time.
- Pond Liner Fleece Underlay vs Geotextile UK — Which Is Better? — Both go beneath the liner. We suggest needled pond fleece for clean, stone-free garden soil and heavier geotextile for flinty or stony ground, steep slopes and commercial ponds.
- Pond Liner Underlay — Complete UK Buying Guide — Yes, use underlay: needle-punched geotextile protects the liner from stones, roots and grit pressed against it by the water's weight.
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- Commercial and Large Pond Lining
Need help choosing? Contact our team or see the pond liner hub.