What drives the price of a geomembrane liner

Buyers reasonably want a rate per square metre. Suppliers reasonably refuse to publish one. Both positions are defensible, because a geomembrane is fundamentally a resin product and resin prices move with oil, feedstock availability, freight and exchange rates. A published rate is either stale or padded enough to survive being stale.

Resin: most of the number

Polyethylene resin typically accounts for something in the range of 60 to 75 per cent of the cost of a finished geomembrane. When resin moves, liner prices follow within a month or two. This is why a quotation from six months ago is not a benchmark, and why a supplier holding a rate open for ninety days is either very confident or building in a cushion.

Resin grade is a separate lever. Virgin resin with a full carbon-black and antioxidant package costs meaningfully more than blended or reprocessed material. Both can be sold as “HDPE geomembrane”. Only one has a mill certificate that stands up.

Thickness and texture

Thickness is close to linear on the material side — 2.0 mm sheet contains twice the resin of 1.0 mm sheet. Texturing adds a modest premium because the production line runs slower and the process is more demanding. Colour options such as white-surfaced sheet are a further premium and usually a made-to-order item.

Where thickness is not linear is installation. Welding 1.5 mm sheet is not fifty per cent more work than welding 1.0 mm. So on an installed price, moving up a gauge costs proportionally less than it does on a supply-only price — which is worth remembering when a specification is borderline.

Order size

Production runs and freight both reward scale. Container quantities carry materially better rates than two-roll orders, and part rolls attract a cutting charge. If you have several basins across a site or a programme, price them as one order rather than three, even if delivery is staged.

The installation half

An installed rate adds welding crew, welding and testing equipment, generators, consumables, mobilisation, and supervision. What moves it most is not area but detail count. A crew welding 300 metre panel runs across an open reservoir covers ground fast; the same square metreage split into small basins with thirty pipe penetrations is slow, skilled, extrusion-welded work.

Other things that move an installed price:

• Access — whether a telehandler can reach the crest with a tonne roll.
• Programme — night works to avoid summer heat, or two crews to hit a date.
• Testing scope — standard air and vacuum testing is included; destructive coupon frequency and electrical leak location surveys are extra.
• Whether subgrade preparation and anchor trench earthworks are in your scope or ours.

Comparing two quotations

Before comparing totals, line up five things:

1. Core thickness, and whether textured sheet is quoted on core or over asperities.
2. Resin grade and whether a batch certificate is offered.
3. Area basis — square metres of sheet, or square metres of basin? Overlaps, anchor trench and slope length can put 15 per cent or more between the two.
4. Delivery — included, or ex-yard?
5. Scope — supply, or supply plus welding plus testing plus documentation?

Two quotes that differ by a third usually differ in scope by a third. Occasionally they differ because one is for a materially inferior product.

When a price is too good

A rate substantially below the market is not automatically a scam, but it usually has an explanation. The common ones are: sheet running below nominal core thickness, reprocessed resin content, missing or generic certificates, a supply-only rate presented against an installed scope, or testing and documentation quietly excluded.

Ask which one it is. A supplier who can explain a low price — excess stock of a gauge, a container arriving anyway, a quiet month for the crew — is fine. One who cannot is telling you something.

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