HDPE Pond Liner UK | Lifetime Guarantee | Heavy Duty Underlay Included | 0.35mm

HDPE Pond Liner with Lifetime Guarantee and Heavy Duty Underlay

This is the version to choose when the ground under your pond is not kind: stony soil, roots, flints or an uneven base. It pairs a 0.35mm black HDPE (high-density polyethylene) pond liner, carrying a lifetime guarantee against sunlight damage, with a heavy duty underlay included in the price. Together they give you long-term UV cover on top and extra cushioning underneath. It comes in 35 pre-cut sizes from 2m x 2m right up to 30m x 40m, so it suits anything from a small fish pond to a large wildlife lake, in a single sheet with no joins.

Why it works

The guarantee covers the sun; the underlay covers the ground

A liner usually fails in one of two ways. The exposed edge between the waterline and the coping is slowly attacked by sunlight, and the underside can be pierced by a stone, a root or settling ground. The lifetime guarantee on this liner is against damage caused by sunlight exposure; it does not include punctures or tears. That second risk is exactly what the heavy duty underlay is there to reduce, so this listing gives you both halves of the protection in one order.

Strong, but still flexible to install

At 0.35mm the HDPE sheet is strong enough for long outdoor use yet flexible enough to fold into shelves, corners and curves. It is lighter than rubber, which makes it easier to handle and pleat neatly, although the larger sizes are a job for two or more people.

• Lifetime guarantee against sunlight damage
• Heavy duty underlay included with every size
• 0.35mm HDPE: strong, light and flexible
• Sizes up to 30m x 40m in one sheet

Where it's used

Fish and koi ponds dug into flinty or stony soil, wildlife ponds near trees where roots are a concern, decorative water features with rockwork, and large garden lakes where one join-free sheet saves time on site. Landscape contractors use the heavy duty underlay version where they cannot fully control the base.

Specifications

Choosing the right size

Measure the longest length, the widest width and the deepest point of the pond, then work out each direction separately:

Liner length = pond length + (2 x maximum depth) + 0.6m
Liner width = pond width + (2 x maximum depth) + 0.6m

The extra 0.6m leaves a 30cm overlap on every edge for anchoring. Round up to the next size available; sizes work either way round. For example, a 3m x 2m pond that is 0.6m deep needs at least 4.8m x 3.8m, so choose 4m x 6m. A 4m x 3m pond at 0.75m deep needs 6.1m x 5.1m, which points you to 6m x 7m. If you are between two sizes, go up. Not sure? Use the pond liner size calculator.

Choosing between our lifetime HDPE liners

If your ground is soft, sandy and stone-free, the lifetime HDPE liner with standard underlay does the job for less. Choose this heavy duty underlay version for stony, flinty or root-filled ground, for deeper ponds with more water weight on the base, or simply for the extra margin of protection.

Installation, use and care

Dig the hole with shelves where you want marginal plants, then remove sharp stones and roots and firm the base. Lay the heavy duty underlay first, then unfold the liner on a warm day so it relaxes and centre it over the hole. Fill slowly, easing the liner into the corners and folding neat pleats as it settles. Once full, trim the edge leaving the 30cm overlap and bed it under your coping.

Frequently asked questions

What does the lifetime guarantee cover?

It covers damage caused by sunlight exposure for the life of the liner. It does not include punctures or tears, which is why the heavy duty underlay is supplied and why the base should be cleared of sharp stones and roots.

Is the heavy duty underlay included with every size?

Yes. Every size in this listing comes with heavy duty underlay at no extra cost.

What kind of ponds is it suitable for?

Fish ponds, wildlife ponds and decorative water features of all shapes and sizes.

Ordering

Pick your size from the list; each one is a single pre-cut sheet supplied with its heavy duty underlay. Because liners are supplied cut to size, please check your measurements with the formula above before ordering, and see our returns policy for details. Our team is happy to help you confirm the right size.

Helpful guides

• Pond liner sizing: measure and order the right size
• Pond liner installation: all guides
• Pond liner underlay guides
• HDPE pond liners