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Waterproof-breathable fabrics explained

If you’ve ever wondered what is meant by ‘DWR’, ‘tricot’ or ‘water-resistant’, you’ll find answers to your questions about waterproof fabrics right here.

waterproof symbol

If you’ve ever found yourself trying to choose between two waterproof jackets and wondering what was meant by ‘tricot’, ‘DWR, or ‘water-resistant’, this article is for you. In this gear guide, I’m going to go into the technology used in waterproof fabrics and the things you might want to consider when choosing your next piece of rainwear. Just know that it’s going to get a little nerdy as this is the most technical article in a whole series on waterproof garments. If you are looking for something more general, like how to choose a rain jacket or an article explaining the differences between a soft shell and a hard shell, I have articles on those too.

Waterproof vs water-resistant

To ensure proper protection in the conditions you expect to face, it’s important to know the difference between the three levels of water protection afforded by fabrics. To be clear, the industry has yet to develop a standardized system for rating the water resistance of fabrics, and what I have done here is use designations where there is the most consensus among brands. Thankfully, many manufacturers have performed a more or less standardized test, which makes it possible to make comparisons. In a hydrostatic head test, an open-ended cylinder is placed on top of a piece of fabric and slowly filled with water. Results are measured in how much water the material can be exposed to (in milimeters) before it begins to seep.

Water-resistant (0 to 1,500 mm)

‘Water-resistant’ means that a fabric is tightly woven or manufactured in such a way that it resists penetration by moisture. But that doesn’t mean much. A garment made from water-resistant fabric won’t keep you dry in much more than a misty morning fog or a little drizzle. This is the lowest level of protection against moisture. Water-resistant fabrics perform very poorly in hydrostatic head tests and usually aren’t even tested.

Water-repellent (1,500 to 5,000 mm)

Water-repellent fabrics have one up on water-resistant fabrics in that they have a durable water repellent (DWR) coating which causes water to bead and roll off a jacket instead of soaking through it. This slows the speed at which a jacket becomes saturated in sustained rain. Because they don’t have waterproof membranes, water-repellent fabrics are only good for keeping you dry in light rain and are not sufficient for rainwear.

Waterproof (over 5,000 mm)

A waterproof layer will protect you in moderately heavy to very heavy rain depending on its rating. In very wet conditions, a fabric rated to 10, 000 mm will keep you drier than one rated to 5,000 mm, but above 20, 000 mm there is little notable difference in performance. Garments deemed waterproof typically have a DWR-treated face fabric and a waterproof-breathable membrane. Beyond this, they also need to have sealed seams (taped or heat welded) to ensure that water doesn’t get through the seams.

waterproof levels

Waterproof fabric construction

Before we can get into 2L, 2.5L and 3L fabrics, we need to understand what is meant by ‘DWR’, ‘face fabric’ and ‘inner lining’ – elements commonly incorporated into waterproof-breathable fabrics. 

Durable waterproof repellent

Durable waterproof repellent (DWR) is the coating that causes water to bead up and roll off the outer layer (face fabric) rather than be absorbed. In most membrane fabrics, this hydrophobic function has no impact on waterproofness, but what it does do is help maintain breathability. A shell that has absorbed water and ‘wetted out’ cannot breath, something that DWR helps prevent.

Face fabric

The outer layer or face fabric protects the waterproof membrane and provides a surface on which to apply DWR. Typically made from nylon or polyester, this layer can be thicker and more durable or thinner and lighter. Hard shells typically use 50 to 75-denier polyester while lighter rain shells are usually made with 20 or 30-denier nylon. The higher the denier number, the thicker the fabric. 

Sealed seams

The problem with stitched seams is that they create thousands of tiny holes for water to get through. To make a garment properly waterproof, the seams have to be sealed. That can mean either taping up stitched seams or foregoing stitches altogether and heat-welding panels together instead. Soft shell jackets, even those with membranes, have unsealed seams, making them merely water-repellant.

Inner lining

After the face fabric and membrane, 3-layer fabrics have an inner tricot lining. The main purpose of this layer is to protect the membrane and prevent it from becoming clogged with dirt and oil, but it also adds a level of comfort and helps wick away sweat to prevent clamminess. The inner lining in 2-layer garments, on the other hand, is not bonded to the membrane and is considered a separate fabric.

2-layer and 3-layer shells

2L, 2.5L and 3L fabrics

To help you stay dry, a fabric has to be both waterproof and breathable (allow water vapor to escape). It if isn’t breathable, perspiration will build up on the inside of the garment, and you will still feel wet. While 2-layer, 2.5-layer, and 3-layer fabrics are all waterproof, they differ in terms of breathability and durability.

3L fabrics

In 3-layer fabrics the waterproof-breathable membrane is sandwiched between the face fabric and a protective inner lining. Again, the main purpose of this last layer is to prevent sweat and oils from clogging the microscopic holes in the membrane – something that would hinder breathability and make the wearer clammy with perspiration. It is this ability of the lining to prevent a membrane from becoming fouled that gives 3-layer fabrics an advantage over comparable 2.5 layer fabrics. The disadvantage of 3L fabrics is that they are slightly heavier than 2.5L fabrics (2L garments have a separate inner lining and can actually be heavier). As with 2L and 2.5L fabrics, the degree to which a 3L fabric is breathable depends on the type of waterproof-breathable membrane.

2.5L fabrics

Although lighter, fabrics with a 2.5-layer construction look similar to 3-layer fabrics. They also have DWR-treated face fabric and a waterproof-breathable membrane. But instead of having a protective lining bonded to the inside of the membrane, 2.5L fabrics have a thin protective coating (the 0.5 layer) painted onto the inside of the membrane. In the past, these coatings weren’t as good at absorbing and transmitting perspiration as a tricot lining, and many 2.5L shells left wearers feeling a bit clammy when they were worn next to skin. But recent developments in 2.5L fabric construction have helped improve the clammy factor, and some 2.5L shells are now almost as comfortable as 3L equivalents.

2L fabrics

Traditionally, 2-layer shells have had a face fabric bonded to a waterproof-breathable membrane with a loose (typically mesh) protective liner hanging inside them. Although more affordable, these mesh-lined 2L garments are generally heavier, bulkier, and less comfortable than 2.5L and 3L equivalents. Enter Gore-Tex Paclite Plus. This innovative 2L fabric also features a face fabric laminated to a waterproof-breathable membrane, but then instead of adding an separate mesh lining (or protective coating as used in 2.5L fabrics), Gore-Tex has textured the inside of the membrane in such a way that it increases abrasion resistance and makes an additional protective layer unnecessary.

cross-section of Gore-Tex fabric

Waterproof-breathable membranes

Making a garment waterproof isn’t difficult, but making it waterproof and breathable is. To overcome this challenge, gear manufacturers have all turned to the same solution, a waterproof-breathable membrane. The original ePTFE membrane was produced by Gore-Tex, a brand that dominated the market for decades. 60 years on, there are now  four different types of waterproof-breathable membranes and a dozen companies making them. This is what you need to know about the pros and cons of each.

Air-permeable membranes

Because they are porous, air-permeable membranes allow for the transmission of air and water vapor molecules, making them significantly more breathable than vapor-permeable membranes, which don’t allow air to pass through them. Given how important breathability is for preventing the build up of sweat during exercise, this type of membrane is often a better choice for physically intense activities.

ePTFE

Expanded polytetrafluoroethylene, or ePTFE for short, is the material that was first used in waterproof-breathable membranes. Because it doesn’t need to be as thick as polyurethane, it can be made thinner and more breathable than polyurethane film equivalents. The downside to ePTFE membranes is that they can become fouled more easily (impairing breathability) if exposed to oil and dirt and need to be washed regularly to ensure breathability and longevity. Products include Gore-Tex Pro and eVent, the two most expensive outdoor fabric brands on the market.

membrane logos

Electrospun polyurethane

Because they are non-porous, regular PU film membranes (described under vapor-permeable membranes) are inherently less breathable than ePTFE membranes. To overcome this limitation and improve breathability, a few fabric manufacturers have started using electrospun polyurethane to make porous membranes. The result is a type of air-permeable membrane that is almost as breathable (or even as breathable) as ePTFE membranes and only slightly less waterproof. Fabrics include Polartec NeoShell, Outdoor Research AscentShell, and The North Face FutureLight.

membrane logos

Vapor-permeable membranes

Unlike air-permeable membranes, vapor-permeable membranes are non-porous, meaning that air cannot pass through them. To achieve breathability, vapor-permeable membranes allow the transmission of water vapor through molecular wicking. This makes them inherently less breathable than air-permeable membranes, although the degree to which they are less breathable varies significantly between the two types of vapor-permeable membrane.

ePTFE-PU

Unlike Gore-Tex Pro, which has an ePTFE-only membrane, regular Gore-Tex features an ePTFE membrane bonded to a thin PU film. The purpose of the latter is to help prevent oil and dirt from clogging the membrane, the achilles heel of true ePTFE membranes. The result is a membrane that is less breathable than ePTFE membranes but more breathable than PU membranes. This type of hybrid membrane also splits on the difference on resistance to fouling and sits between the two in terms of price. Achieving a happy middle ground in all aspects of performance, Gore-Tex is still the most popular of waterproof-breathable fabrics.

membrane logos

Polyurethane film

Because they don’t incorporate any other membrane layers, PU film membranes have to be thicker to ensure the same level of waterproofness. Being thicker and entirely non-porous, these membranes are less breathable than other types of membrane, especially in humid conditions. But PU films also have their advantages: they are very durable and don’t become fouled by dirt and oil as easily as ePTFE membranes. And they are more affordable than any other type of membrane, making them a popular choice for proprietary fabrics like Patagonia H2No, Marmot NanoPro, and Columbia OmniShield.

membrane logos

Get more advice from this gearhead

You now have everything you need to know about waterproof-breathable fabric. But don’t stop here. If your next purchase is going to be some kind of waterproof jacket, I strongly recommend reading my guide on how to choose rainwear next. Or maybe you haven’t even decided between a soft shell or hard shell yet, in which case my guide to outdoor jackets might help you to make a decision. You’ll find all of these and more right here under GEAR in the Outdoor life category. Alternatively, sign up for my newsletter to get all the latest from Trail & Crag delivered