Making Sense of Waterproof Ratings on Your Ski Gear

Confused about the different lingo surrounding waterproof ski gear? You're not alone! Check out this guide for a better understanding of waterproof technology!

A skier turning down a mountain in very snowy conditions.

Photo by Maarten Duinevel

When shopping for outerwear, it is easy to get overwhelmed by the mass of technical lingo, abbreviations, materials, coatings, and other seemingly nonsensical technology seen in ski gear descriptions. With so much proprietary tech and a huge range of gear quality on the market, a standardized rating system that distinguishes gear quality in a consistent way across all brands would be immensely beneficial. Fortunately, a system like this already exists!

The standard test procedure for both waterproofing and breathability is consistent enough for manufacturers to compare their technology in the lab and provide the consumer with an index number to better estimate the intended use of the garment. While these numbers are not perfectly consistent across brands, they give a great launching point for learning about your apparel before exposing them to the harsh elements of the mountains.

Waterproof Testing

A diagram showing how waterproof testing on fabrics is done.

Diagram by Hunter Reed

Most ski apparel has its waterproof rating tested by a hydrostatic head test. This test uses a machine to determine the garment's ability to withstand water intrusion by pulling the fabric tight and subjecting it to pressurized water. By slowly ramping up the pressure of the water and observing the water penetration, the fabric’s waterproof rating can be determined. These machines are made to replicate the standard water permeability resistance test in a much more compact package.

Water permeability resistance is basically the fabric's resistance to water. The commonly discussed test in outdoor waterproof ratings is the static column test, which places a one-inch-diameter cylinder over the fabric and slowly fills it with water—observing when the water begins to leak through the fabric. When you see a waterproof rating of 5k or 5,000mm, this means that the garment was able to withstand 5000mm of water in the cylinder before it started to leak.

But, this hypothetical cylinder does not exist; and if it did, it would need to be five meters tall for the above rating, or 25 meters tall for more technical apparel. This is where devices like the hydrostatic head test machine come into play.

Waterproof Ratings

Understanding that ski gear is rated by the amount of water that exists is a great start when shopping. Typically ski gear ranges from 5000mm (5k) to around 25,0000mm (25k), with exceptions on either side of these ratings. The categories below are intended to help you understand waterproof ratings and their intended use:

Below 5,000mm

Fabric that is below 3,000mm is generally not considered waterproof and fabric below 5,000mm is usually reserved for ultralight or highly packable jackets. These are meant to protect you from light rain but generally will not do much in more inclimate weather. Some snow gear is rated below 5k with the intention of being used strictly for fairweather skiing or spring laps in the park.

5,000mm

Apparel that is rated at 5k is not common and is a low starting point for ski-jacket waterproofing. This rating will keep you dry in light rain, low amounts of snowfall, and when exposed to minimal pressure from blowing snow or rain. Generally, garments in this range are for less serious skiers and riders or those looking to only use the apparel in more average conditions.

10,000mm

Gear that is rated at 10k or above is considered standard in the ski industry. Most branded snow apparel has at least a 10k waterproof rating and will protect you in moderate rain, most average snow conditions, and will also hold up under some pressure such as sitting on a chairlift, wearing a backpack, etc.

15,000mm

Gear rated at 15k or above is the standard for performance gear that will provide adequate waterproofing for most days. Innovations in fabric and workmanship technology have made gear with a 15k waterproof rating affordable and accessible to most skiers. When taken care of properly, products with a 15k rating will keep you dry in most weather conditions except under high pressure.

20,000mm

Gear rated at 20k is more common in higher-end ski apparel. This rating is more often found in shell-style gear that is made for the sole purpose of protection from the elements. These types of jackets, pants, and bibs, are more common for skiers who are putting in a higher number of days at the mountain and who are often found skiing despite the weather. 20k gear can hold up to heavier rains, more serious snow storms, and resists leakage even when exposed to higher pressures.

25,000mm

Gear above 25k is usually reserved for specialty-branded fabrics such as GORE-TEX (which is rated at 28,000mm) and is found on the highest-end equipment. Gear at this rating can withstand harsh blizzards, heavy downpours, or serious pressures. This type of waterproof rating is best for skiers or riders looking to make no sacrifices in their equipment.

Additional Water Resistance Technology

Waterproof fabric with some areas soaked through and some areas holding beaded up water.

Photo by Alinja

Along with waterproof ratings, the type of material used, as well as its construction, plays into its ability to keep you dry in inclement weather. Most waterproof ski apparel has multiple fabric layers to comprise the finished material. They typically consist of three layers comprising an outer shell, a waterproof membrane, and an inner liner, but this can vary with different manufacturers. The middle layer—the membrane—is responsible for the majority of the waterproofing and does this via micro pores that allow air out but don’t let water in.

Layers (2L, 2.5L, 3L)

As mentioned above, most ski apparel has a three-layer (3L) construction. Though occasionally garments are made of fewer layers and skip the liner or inner protective scrim or sometimes add additional protection to the membrane with an inner coating. These garments—known as 2.5L garments—function well and are typically lighter but also not as warm as their 3L counterparts. Also, some garments have just a waterproof membrane with a bonded outer face fabric, and if they have an inner liner it is typically fabric that is only partially bonded to the outer layer; these are called 2-layer (2L) garments, and they are typically not as durable as their higher-layer counterparts.

DWR Treatment

Additional waterproofing is often applied to winter garments in the form of an outer coating. This durable water repellent (DWR) causes water to bead up and roll off of the exterior of the jacket. Because this coating is applied to the fabric, and is not a characteristic of the fabric itself, it tends to lose its effectiveness over time. It is also possible to reapply DWR to your garments at home.

Seam Sealing

Often a weak point in your garment's waterproofing, the seams of your apparel have different options for additional waterproofing. Taped or sealed seams cover the stitching with an additional layer to prevent water penetration. Critically taped seams have waterproof tape over the most important seams and are typically found in cheaper jackets. Fully taped seams cover every possible water entry point and provide better protection from the elements. Welded seams skip the stitching altogether and bond the fabric to itself at the seam to best protect it from water leakage.

Other Tech

There is plenty of other tech—mostly proprietary or material based—that is unique to specific brands or products. It's worth paying attention to the type of materials used, special laminates, or types of coatings. Most brands make their garments either out of thermoplastic polyurethane (TPU), polyurethane (PU), or expanded polytetrafluoroethylene (ePTFE). TPU and PU materials are constantly improving but are a little slower to evaporate. ePTFE is commonly found in higher-end materials like GORE-TEX, but many companies are moving away from it due to its negative environmental impacts.

Final Thoughts

A skier heading down a mountain with a cloud of snow behind him.

Photo by Maxi Am Brunne

With so much proprietary tech and marketing lingo surrounding winter apparel, choosing the right gear can feel daunting. Fortunately, there are some standard tests and procedures between manufacturers that help consumers distinguish between apparel with lower water resistance and those with higher levels of waterproofing. As a consumer, it is best to know the type of materials and their associated ratings when choosing gear to make sure that your money is well spent.

Equipped with all of the essential layers for staying comfortable on the hill, you will stay warm and dry no matter the conditions on the mountain. Understanding your waterproof ratings will help you get the most out of the stormy days on the hill and keep you smiling and shredding pow well after the crowds head home. Contact Winter Sports Expert for any questions you may have about gear choice; we’d be happy to help.

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Written By
My name is Gunnar and I live and ride in Washington 🏔🌲. I'm primarily a skier ⛷ but you can occasionally find me on a snowboard 🏂. I love deep days 🌨 and finding new ways to ride terrain 🧑‍🎨. It doesn't matter if I am getting first tracks right under the chair 🚠 or hanging off a tree branch t...

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