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Waterproof & Breathability Ratings Explained

Ski wear is sold as 5K, 10K, 15K or 20K. The number is the fabric's waterproof rating in millimetres, measured in a lab. This guide explains what the ratings mean, how breathability is measured, why seam taping matters as much as the fabric, and how we specify and test the rating for your order.

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  • 50 pcsMinimum order
  • 14 daysStandard lead time
  • OEKO-TEX®Fabrics from certified mills
  • ISO 9001Certified (Eco Jersey Limited)
  • SedexMember (Eco Jersey Limited)

The basics

What a waterproof rating measures

The rating comes from a hydrostatic head test. A sample of fabric is clamped under a column of water, or under water pressure that rises steadily, until drops come through. The height of the water column at that point, in millimetres, is the rating: a 10K fabric held back 10,000 mm of water. Common test methods are ISO 811 (EN 20811), AATCC 127 and JIS L 1092.

  • It rates the fabric, not the garment

    A jacket can leak at the seams, zips and cuffs even when its fabric has a high rating. That is why seams are taped.

  • Pressure is higher than rain

    Kneeling or sitting in snow, a backpack strap and wind-driven snow all press water into the fabric, so ski wear needs more than a light rain jacket.

  • It can drop with wear

    Abrasion, flexing and washing wear the coating or membrane over time. A higher starting rating leaves more margin.

Ratings

5K, 10K, 15K and 20K compared

We make ski wear in these four ratings. The conditions are a general guide used across the industry; the right rating also depends on the price point and on how the garment will be worn.

RatingWater columnTypical conditionsCommon use
5K5,000 mmDry snow, cold and clear days, short sessionsEntry-level and kids' ski wear, school trips, promotional and event wear
10K10,000 mmAverage resort skiing, moderate snowfallMost resort jackets, pants and suits; team and club wear
15K15,000 mmHeavy or wet snow, long days on the mountainInstructor and staff uniforms, premium resort ranges
20K20,000 mmVery wet snow, storms, sitting or kneeling in snowFreeride, backcountry and technical shells, snowboard wear

Breathability

How breathability is measured

A waterproof fabric must also let sweat vapour escape, or the wearer gets wet from the inside. Breathability is quoted in two ways, and the numbers from different methods cannot be compared with each other.

MeasureWhat it meansHow to read it
MVTR (g/m²/24h)Grams of water vapour that pass through one square metre of fabric in 24 hours; methods include JIS L 1099 and ASTM E96Higher is more breathable. Often paired with the waterproof rating, as in "10K/10K"
RETResistance to evaporative heat transfer, measured with ISO 11092Lower is more breathable: below 6 is usually called extremely breathable, 6 to 13 very breathable

A coated shell usually breathes less than a laminated one at the same waterproof rating, and a 3-layer laminate usually breathes best. Vents, such as underarm zips, add breathability that no fabric test shows.

Construction

Seam taping and water-repellent finishes

Two details decide whether the fabric rating holds in the finished garment.

  • Critical-seam taping

    Only the most exposed seams, such as shoulders, hood and upper back, are taped. It keeps cost down but leaves the other seams open.

  • Fully taped seams

    Every seam is sealed on the inside with waterproof tape. We offer fully taped seams for waterproof ski wear.

  • Water-repellent finish

    A finish on the face makes water bead and roll off, so the fabric does not soak up water and the membrane keeps breathing.

  • Re-proofing

    The water-repellent finish wears with use and washing. Care labels can tell the wearer how to wash and re-proof the garment.

For your order

How we specify and test the rating

The rating is part of the specification we agree with you, and an independent lab can check it on request.

  1. Choose the rating

    Tell us where and how the garment will be worn. We suggest a rating, a shell fabric and a waterproofing build that fit the price point.

  2. Agree the specification

    The fabric, the waterproof rating and the seam taping are written into the tech pack and the approved sample.

  3. Independent testing

    Independent lab testing of the waterproof rating can be arranged on request, so you don't have to rely on our word.

  4. Test it yourself

    You are welcome to test the fabric or the finished garment at any lab you choose, against the specification we agreed.

FAQ

Waterproof ratings: frequently asked questions

What does 10K/10K mean?

The first number is the waterproof rating, 10,000 mm of water column. The second is the breathability, 10,000 g of water vapour per square metre in 24 hours. It is a common mid-range specification for resort ski wear.

Which waterproof rating do I need for ski wear?

10K suits most resort skiing. 5K is enough for dry, cold conditions, kids' wear and entry-level ranges. 15K and 20K are for wet snow, long days outdoors, staff uniforms and freeride or snowboard wear.

Is a higher rating always better?

Not always. Higher ratings cost more and a coated fabric at a high rating can breathe less. Choose the rating for the conditions, and make sure the seams are taped; an untaped 20K jacket leaks sooner than a fully taped 10K jacket.

Can I have your fabric tested before bulk production?

Yes. Independent lab testing can be arranged on request, and you can send the fabric or a sample garment to any lab you choose to test it against the agreed specification.

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