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How to fit a pond liner

Updated: 22 October 2026

The sheet is in the hall, or it is still in the basket, and the usual failure is a rectangle ordered to the water surface, cut before the pond is full, or laid on stones with nothing underneath. This is how to fit a pond liner with the flexible sheets in this amazon.co.uk set: work out a rectangle you can name, protect the ground, fill so the water seats the sheet, and trim only after that. Product rows and GBP prices are on the [pond liner comparison](/hub/garden-ponds/pond-liner). Peter F. used those listings and the public fitting notes below, and did not dig a pond. A qualifying purchase can earn us a commission at no extra cost to you.

The sheet is in the hall, or it is still in the basket, and the usual failure is a rectangle ordered to the water surface, cut before the pond is full, or laid on stones with nothing underneath.

Our top picks

PondKraft PondKraft 4 m × 4 m pond liner

Best overall

PondKraft PondKraft 4 m × 4 m pond liner
9.2/10about £28.99
View offer
Storystore Storystore 3 m × 3 m pond liner

Best value

Storystore Storystore 3 m × 3 m pond liner
8.8/10about £14.99
View offer
GARDENIX GARDENIX 1 m × 1 m pond liner

Rank 3

GARDENIX GARDENIX 1 m × 1 m pond liner
8.6/10about £6.72
View offer
On this page
  1. 1.Work out the rectangle
  2. 2.Prepare the ground
  3. 3.Fill, then fold, then trim
  4. 4.Cover the edge

Work out the rectangle

Measure maximum length, width, and depth. Add twice the depth to the length and to the width, then add overlap and round up. AllPondSolutions says a short sheet cannot be extended. Order the water surface and you are already short by the depth on every bank. The overlap figures do not agree. The Royal Horticultural Society says about 15 cm all round. AllPondSolutions' field is 30–50 cm. A GARDENIX bullet says at least 50 cm, and do not cut until the liner is full. The Conservation Handbooks butyl note uses 300 mm and says cut once full. That 300 mm is the handbook's figure, not the RHS figure. Which material belongs in the rectangle is on the pond liner buying guide.

Prepare the ground

Take out stones, roots, and slate before any sheet goes down. On stony ground the RHS asks for about 2.5 cm of sand and then underfelt. The RSPB page says about 50 mm of sand and underlay, and says do not cut yet. Saved texts on the 0.1 mm rows describe holes from gravel or slate. A PondKraft text describes an install on sand and geotextile that still lost water, so fleece is protection, not a guarantee. AllPondSolutions says underlay is not waterproof. Butyl Products says geotextile can wick water out if it bridges the edge. MuAnWei's 10 nails of 16 cm are not a fixing method: a nail through the film is a hole.
PondKraft PondKraft 4 m × 4 m pond liner

Testsieger

PondKraft PondKraft 4 m × 4 m pond liner
9.2/10about £28.99
View offer

Fill, then fold, then trim

Lay the sheet loosely, hold the edges with bricks rather than spikes, and start filling. The RHS says fill gradually, then cut. GARDENIX says do not cut until the liner is full and the water has dragged it down. Creases on polyethylene are normal. Saved reviews say these sheets have no stretch, and some compare a sheet to tarpaulin. Pleat the spare. Do not stretch HDPE into a corner, and do not cut a dart out of the water-holding area. If a parcel arrives welded to itself, measure the open sheet against the title before you finish the hole. Then trim to the overlap your source stated.

Cover the edge

The Wildlife Trusts say butyl degrades in sunlight, so cover it. That sentence is about butyl on their page, and it is still a reason to hide these sheets. Bury the overlap, or cover it with stone, paving, or soil, so the waterproof sheet caps the fleece. Fleece or turf that runs from the water onto the bank can wick the pond empty. A wildlife beach and the advice not to add fish are on pond liner for a wildlife pond. They change the rim. They do not change fill, then trim. If you are holding a butyl stretch method against HDPE film, read EPDM or HDPE pond liner before you force the corners. Ask for advice when the hole is large or deep beside a boundary or a listed building, when you may harm great crested newts, or when the pond will connect to a watercourse.

Common questions

What measurements do I add before I order?
Add twice the maximum depth to the length and to the width, then add overlap and round up. A 2 m by 1.2 m pool at 45 cm deep is 2.9 m by 2.1 m before overlap. The RHS uses about 15 cm, AllPondSolutions uses 30–50 cm, and a GARDENIX bullet says at least 50 cm. Keep the figure with the source. Ordering the water surface leaves you short on every bank.
What goes under the sheet, and what must not be used as the waterproof layer?
Sand and geotextile protect the liner. They do not hold water. The RHS suggests about 2.5 cm of sand on stony ground, then underfelt. The RSPB suggests about 50 mm of sand and underlay. Fleece left bridging the rim can wick the pond out. A listing ranked as underlay is still a liner unless a second fleece is in the box.
When do I cut?
After the pond is full and the water has pulled the sheet into the hole. That is the GARDENIX bullet, and it matches the RHS order of fill, then cut. Leave about 15 cm if you are following the RHS, or at least 300 mm if you are following the Conservation Handbooks butyl note. Cutting to the waterline while the sheet still bridges the hole leaves you short.
What if the sheet will not stretch into the corners?
Pleat it. Reviews of these polyethylene listings describe no stretch, and cracking when a sheet is forced. Butyl guides that say ease the rubber into the shelf do not apply to 0.1 mm HDPE. If a pleat will not sit after filling, the sheet is short or the ground is proud. Do not cut a piece out of the bottom and tape it.
Can I nail the sheet into the soil?
Not through the part that holds water. MuAnWei includes 10 nails of 16 cm. A nail in the basin is a hole. Hold the dry edge with bricks while you fill, then bury or cover the overlap. A peg belongs outside the water, and not through fleece that can wick.

Related pages

Pond pump comparison

Pond liner

Best pond liner: stated thickness, not the star line

Pond liner buying guide: size, material and thickness

EPDM or HDPE pond liner: these sheets are not rubber

Wildlife pond liner: shallows, a beach and a cover

Sources

Public UK sources for this comparison. Listings and prices were taken from amazon.co.uk on 21 October 2026.

  1. RHS: How to make a new pond (retrieved 21 October 2026)
  2. Freshwater Habitats Trust: frequently asked questions (retrieved 21 October 2026)
  3. Planning Portal: permissions for a garden pond (retrieved 21 October 2026)
  4. Keeping and Introduction of Fish (England and River Esk Catchment Area) Regulations 2015 (retrieved 21 October 2026)
  5. GOV.UK: introduce or keep non-native fish, lobsters and crayfish (retrieved 21 October 2026)
  6. GOV.UK: great crested newts, protection, surveys and licences (retrieved 21 October 2026)
  7. Water Garden: pond liner materials (retrieved 21 October 2026)
  8. Consumer Rights Act 2015, section 9 (retrieved 21 October 2026)