EN 343 waterproof clothing: what the two numbers mean
EN 343 rates protective clothing against rain on two separate scales, both shown next to the pictogram: resistance to water penetration and resistance to water vapour, which is breathability. Each is expressed as a class from 1 to 4, and a higher class number is better in both cases.
The standard uses two numbers because the properties pull against each other. It is easy to make a garment no water gets into, and much harder to make one that also lets sweat vapour out. A waterproof that fails on the second count leaves the wearer just as wet by the end of a shift, from the inside.
- EN 343 gives two class numbers, 1 to 4: water penetration resistance first, then water vapour resistance. Higher class is better in both.
- Breathability is measured as Ret, and a lower Ret value means more breathable. The class number rises as the Ret figure falls.
- Class 1 breathability carries a restricted wearing time, so it is a poor choice for a full shift of active work.
- An optional rain tower test on the finished garment is shown as R. If it was not carried out, an X appears instead.
- EN 343 covers rain only. Visibility, insulation against cold and chemical splash are separate standards.
Reading the marking
The EN 343 marking is a short stack of characters beside the rain pictogram, in a fixed order:
- Water penetration resistance, class 1 to 4, from a hydrostatic head test on the fabric and, at the higher classes, on the seams after pre-treatment such as washing or abrasion.
- Water vapour resistance, class 1 to 4, from the Ret value of the fabric.
- The optional rain tower test, shown as R when the finished garment has passed and X when it was not carried out.
Pre-treatment is the part skipped in sales copy and the part that matters in service. The higher water penetration classes require the fabric to still perform after treatment, which is a closer proxy for a jacket that has been through a site laundry a dozen times.
Water penetration classes
Water penetration resistance is measured as a hydrostatic head: the column of water the fabric holds back before letting water through. In metres of water column, the thresholds run as follows.
- Class 1 - at least 0.8 m, tested on the material as supplied.
- Class 2 - at least 0.8 m, tested after pre-treatment.
- Class 3 - at least 1.3 m after pre-treatment.
- Class 4 - at least 2 m after pre-treatment, with the seams also tested after pre-treatment.
For sustained outdoor work in British weather, class 3 or 4 is the sensible starting point. Class 1 and 2 garments suit short exposure, moving between vehicle and building, but they are not shift-long rainwear. Whatever the class, the failure point in service is rarely the middle of a panel: it is seams, storm flaps, cuffs and hoods.
Breathability, and why lower Ret is better
This is where the confusion lives. Ret is a resistance: how much the fabric obstructs water vapour passing through. A low Ret means vapour escapes easily, so the garment is more breathable. The class number runs the other way, because a higher class is always better performance.
- Class 1 - Ret above 40. Least breathable.
- Class 2 - Ret above 25 and up to 40.
- Class 3 - Ret above 15 and up to 25.
- Class 4 - Ret of 15 or below. Most breathable.
So "Ret 12" beats "Ret 30", while "class 4" beats "class 2". Both are consistent, the numbers just move in opposite directions. At the lowest class the wearing time is restricted, because the wearer's own moisture has nowhere to go. Expensive waterproofs that live in the back of the van usually fail on this figure rather than on waterproofing.
The optional R, and what it adds
The fabric tests above are run on material samples. The optional rain tower test is run on the whole finished garment, worn, under a simulated shower of high energy droplets, and looks for water getting in at the places a fabric sample cannot reveal: seams, closures, pocket entries, hood and cuff design.
A garment marked R has passed that test. An X means it was not carried out, which is not a failure and not unusual, but it does mean the design has not been assessed as a complete system. For people who stand in weather all day rather than dash through it, R is a meaningful discriminator between two similar specifications.
What EN 343 does not cover
- Visibility. High visibility performance is a separate standard with its own classes and colours. A garment can be excellent rainwear with no visibility certification at all, so on any site or rail environment requiring hi-vis, check for both markings.
- Cold. Waterproof is not insulated. Protection against cold is assessed by different standards, and a shell alone relies entirely on what is worn under it.
- Chemical splash. Rainwear is not chemical protective clothing, even where the coating looks similar.
Layering also changes the outcome more than the shell specification does. A class 4 breathable outer over a non-wicking cotton base layer still leaves the wearer damp, because moisture never reaches the membrane to pass through it. Specify the base layer alongside the shell, not afterwards.
Common questions
What is a good EN 343 rating for site work?
For people outdoors for most of a shift, look for class 3 or 4 on both figures: water penetration resistance and breathability. Class 1 or 2 waterproofing suits short exposure only, and class 1 breathability carries a restricted wearing time because the wearer overheats. The optional R marking shows the design was tested as a whole garment.
Does a higher Ret number mean more breathable?
No, the opposite. Ret measures resistance to water vapour passing through the fabric, so a lower Ret value means vapour escapes more easily and the garment is more breathable. The EN 343 class number runs the other way: class 4 is most breathable and corresponds to a Ret of 15 or below, while class 1 is above 40.
Does an EN 343 garment count as high visibility?
No. EN 343 rates protection against rain only and says nothing about conspicuity. High visibility performance is covered by a separate standard with its own classes, background colours and reflective requirements. Many waterproofs are certified to both, but check for both markings rather than assuming one implies the other.
What does the X mean in an EN 343 marking?
X in that position means the optional rain tower test on the finished garment was not carried out. It is not a failure or a zero score, simply the absence of that test. Where R appears instead, the complete garment, including seams, closures and hood, has been assessed under a simulated downpour rather than only the fabric.
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