These are the only measured figures published on this site, and they are worth handling carefully because a service life number detached from its condition is the kind of thing that ends up in a design.
The two positions
Installed in water: approximately 100 years, in submerged service, out of direct UV exposure. Governed by hydrolysis resistance, EN 12447.
Installed on land: approximately 50-100 years, installed and covered within one month of installation. Governed by weathering and oxidation resistance, EN 12224 with BS EN ISO 13438.
Both were confirmed directly by the client during the August 2026 accuracy review. Both derive from retained-strength testing after exposure.
Why two numbers rather than one
Because two different mechanisms govern, and which one applies depends on where the unit sits.
Underwater, the governing mechanism is hydrolysis. There is no meaningful UV, so weathering is not the constraint. Water is a comparatively slow attacker of polyester at ambient temperature, which is why the submerged figure is the longer of the two.
Above water, UV becomes the fastest mechanism by a wide margin, and thermo-oxidative degradation runs alongside it. Left exposed, the material is in the most aggressive condition it will encounter.
So the same product in two positions on the same bank has two different durability stories, and a single blended figure would describe neither.
The conditions are the claim
Stated plainly because it is the point of this page.
“Out of direct UV exposure” is not decoration on the submerged figure. A unit that is submerged most of the year but exposed on a drawdown for months is not in submerged service in the sense the testing addresses.
“Installed and covered within one month” is the load-bearing half of the on-land figure. A unit left uncovered on a bank in full sun for years is not the case that figure describes, and quoting 50-100 years for it would be wrong.
On this site the figure and its condition live in the same data structure and render together, so they cannot be separated by accident. That is deliberate: an earlier unsourced claim of “30 years UV” appeared in 24 places before the accuracy review, and welding each figure to its condition is how that failure mode was closed.
How to quote them in a submittal
Correct:
Service life is approximately 100 years for units in submerged service out of direct UV exposure, evaluated to EN 12447. For units installed on land, approximately 50-100 years where installed and covered within one month of installation, evaluated to EN 12224 with BS EN ISO 13438.
Not correct:
Service life 50-100 years. Service life up to 100 years. 100-year design life.
The second group drops the condition, which changes the claim into one the testing does not support.
What the figures do not mean
Not a warranty. They are durability positions derived from testing, not a guarantee of asset life.
Not a whole-installation life. They describe the mesh. An installation can stop protecting long before the mesh degrades, for reasons that have nothing to do with the material: the bed winnows out from beneath it, the toe is undermined, the edges fail, or the channel keeps degrading. See why scour protection fails.
Not a mechanical wear figure. Abrasion, ice, debris, and vessel impact are separate mechanisms. See puncture, abrasion, ice, and debris.
Not site-specific. Water chemistry, temperature, exposure, and abrasion regime all vary. A warm alkaline reach with heavy bedload is a different condition from a cool temperate one.
Not a substitute for inspection. Whatever the durability position, the installation is inspected. See what failure actually looks like.
Where the design life question actually lands
For most projects the useful question is not “how long does the mesh last” but “does it outlast the asset it protects, and what is the inspection and replacement expectation in the meantime.”
A bridge with forty years of design life left does not need a hundred-year armor material; it needs armor that stays in position through the events of those forty years and can be inspected and topped up. That framing is covered in lifecycle cost vs first cost, including the honest note that we hold no costed lifecycle study.