How do you measure the waterproofness of a hiking jacket?

Coating, membrane, water-repellency: Does that mean anything to you? All these factors will influence the waterproofing of your hiking jacket. How do you measure the waterproofing of your trusty hiking jacket, which you will bring with you on rainy hikes? We explain all!

Your hiking jacket (sometimes called a "hardshell" jacket) is considered waterproof when it is able to stop rain from seeping in. But not all waterproof jackets are created equal! It's easy to get lost in the huge choice of jackets available today. There are different levels of waterproofing and different tests to measure them. To get a clearer understanding, read this article to find out how to measure the waterproofing of a hiking jacket!

Waterproofing and water-repellent properties: what's the difference for your hiking jacket?

You see a "water-repellent" jacket that catches your eye and, what's more, it's less expensive than its "waterproof" counterpart. But these two options don't offer the same technical advantages! So what is a waterproof fabric and why shouldn't it be confused with a water-repellent fabric? Let's look at the difference right away, in order to avoid getting in a muddle!

A fabric's water-repellent property is simply the ability of a material to let water slide off its surface without absorbing it. In practical terms, you'll see drops of water "rolling off" the surface. But it only works if it doesn't rain a lot, and for a short period of time. Its purpose? To give you a back-up solution if you get caught out by a few drops of rain. These products are generally designed for another function, such as providing warmth, and their water-repellent property is a ‘bonus’. They are not really designed to protect you from the rain when hiking. A jacket, that is only water repellent (without being waterproof), is not meant to provide a high level of protection and is only suitable as a "backup" solution. And yes, even if it has a hood, don't be fooled! If there is a risk of rain, be sure to bring a third waterproof layer. If the term "third layer" doesn't ring a bell, we invite you to read this article on <link href="/contents/bc365271-d590-413c-9a76-3d55c48be85b" target="_blank">how to dress for hiking using the three-layer technique</link> (spoiler alert: the third layer is the waterproof layer).

Conversely, the waterproofing of a fabric is its ability to prevent water (rain, snow, dew or moisture) to penetrate a product, such as clothing or footwear.

Whether we're talking about a water-repellent or waterproof product, it's characterised by a ‘chemical’ treatment applied to the product’s material.

In short, a water-repellent fabric is treated on the outside. It has the ability to allow water to “bead” on the surface. The faster the water runs off without seeping in, the more water-repellent the material. So a garment doesn't get waterlogged and stays light. This is due to treatment on the outside of the component.

A waterproof fabric is treated both inside and out: it is a water-repellent material with added protection. This is what prevents water from penetrating the material, even if there is stagnant water or pressure (like that of a backpack) on the fabric.

In short, waterproofing is made possible by a treatment on the outside of the material, but also by waterproofing on the inside. There are two different types: the coating and the membrane.

Is there such a thing as a watertight rain jacket?

You might think that "what goes around comes around", and that a watertight jacket is the ultimate rain jacket? Not really. Because a watertight material is, by definition, one that doesn't let anything through, either way. Whereas a waterproof jacket still wicks away some of the moisture produced by your body using a "breathable" material, a watertight jacket will retain it all. So, yes, you won't get wet from the rain, but you will get wet from your own perspiration. We’ve seen it. Especially as hiking is sport! You're going to sweat (especially if you’re going uphill). So look for waterproof jackets with a tested level of waterproofing that is clearly stated on the product description.

What treatment should be used to make a jacket waterproof?

Two techniques are traditionally used to make a garment waterproof: the coating and the membrane. Don't run off, it's simpler than it sounds!

Coating is a waterproofing material (a kind of paste) applied to the inside of the fabric. It prevents water from penetrating the garment, but can allow water vapour produced by the body's activity to escape from the inside.
The membrane, on the other hand, is a film applied to the inside of the fabric. This hydrophilic membrane blocks water coming from the outside while wicking away the perspiration produced by the active body. The membrane is laminated to the inside the component, making it more flexible and more durable than a coating. You're probably familiar with the famous Gore-Tex® membrane, but there are many other high-performance <link href="/contents/75948c08-4ada-4812-a516-5fb2b89e405d" target="_blank">membranes</link> on the market, designed by different brands.

In addition, the construction of the component is evaluated according to its layers. This is an important "detail" because it will dictate whether your waterproof jacket will be more comfortable or more lightweight, depending on what you prioritise when hiking in the rain.

The 2-layer component: The membrane is glued only to the outer fabric; the inner protective lining is free. This construction is used for the more comfortable jackets.
The 2½-layer component: The membrane is glued under the outer fabric and protected inside by a fine film. This construction is used for the more lightweight jackets.
The 3-layer component: The membrane is glued between the outer and inner fabric.

These highly technical processes justify the price of a good waterproof jacket that will really protect you from the rain.

How can you tell if a jacket is waterproof?

Look at the technical description of the jacket and see if it has ISO waterproofing standards, a full description of the type of assembly and if it has undergone laboratory tests (usually measured in Schmerber). Even if a hooded jacket seems ideal because the name of the product contains the word "waterproof", you may be in for a nasty surprise. Unfortunately, some waterproof jackets are only waterproof in name. For a clearer picture, read the following paragraphs, which explain in detail the waterproofing measurements for rain jackets (but also applicable to other products).

How to measure the waterproofing of a jacket: Two types of tests

The water column test to test the material alone

The first test that is traditionally used to assess waterproofing is the water column test. This test measures a material’s resistance to water pressure. The test results are expressed in millimetres (mm) of water column or mm Schmerber (named after the textile manufacturer Charles-Edouard Schmerber who created this measurement tool). Waterproofing is measured by a material's resistance to water pressure expressed in mm of water column: the higher the pressure, the more waterproof the material is. A component with a 10,000 mm waterproof rating, i.e. it can withstand the pressure of the 10,000 mm column of water. This is also equivalent to 10,000 Schmerbers.

1 Schmerber = 1 mm water column = 0.1 mbar.

At Decathlon we've successively applied two standards to determine waterproof ratings:

The ISO DS006 standard: a column is filled with water at a constant pressure of 60 mbar/min. The test concludes once 3 drops of water have managed to seep through the fabric.
Since 2021, the JIS L 1092 standard from Japan has been applied to Quechua & Forclaz products, as it is the most widely used standard in the outdoor market: a column is filled with water at a faster rate of 1,000 mbar/min. The test stops when the pressure of the water rips the fabric. After testing, our engineers then measure the height of the water to determine the component's waterproof rating. For the same level of waterproofing, the mm water column values (Schmerbers) vary depending on whether they are tested to ISO or JIS standards.

Average rain pressure is between 1,000 and 2,000 Schmerber. A garment that withstands the pressure of a 1.3 metre water column (i.e. 1,300 mm) is therefore considered waterproof (in accordance with ISO standard 811). But be warned that a jacket made from waterproof fabric up to 2,000 mm Schmerber may protect you from the rain, but it may not protect you from a prolonged downpour or thunderstorm. Indeed, the higher the Schmerber number, the more the material is waterproof.

Please note: the quality of the fabric used is very important, because a new rain jacket made from a low-quality material may lose its waterproof qualities after washing. The membrane may be damaged, or the water-repellent property may be reduced. You can reactivate this by using specific products, and washing and drying. But in the case of the membrane, its very integrity is affected... That's why at Decathlon we make sure that our products can claim to be waterproof before and after washing. To make sure your rain jacket stands the test of time, read this dedicated article:

Video: find out how to wash and restore your jacket’s waterproof properties

The shower test to test the jacket from every angle

In this test, the products are placed under a shower to test their overall waterproofing. Yes, a shower! But not quite like the one at home. This one's a lot bigger, so you can test a waterproof jacket by simulating light rain, a storm and everything in between. In our view, this test is the most representative, because a rain jacket made from a highly waterproof fabric will be able to deal with water falling on the seams, the connection between the collar and the hood, the flaps and the zips. In fact, if there are seams, even the most waterproof of materials will have weaknesses because of the holes created by the sewing thread. That's why it's so important to seal the seams, zips, etc. so that there are no gaps for water to seep through.

What waterproof rating can withstand what type of rain when hiking?

Following this test, we can draw up the following rankings to help you choose the best rain jacket for you:

A product with a rating of 2 protects the wearer from a light shower, i.e. 6 mm of rain in one hour (which corresponds to the average rainfall for a month on flatlands in France);
A product with a rating of 3 protects the user from a downpour, i.e. 12 mm of rain in two hours;
A product with a rating of 4 protects the user from a thunderstorm, i.e. 30 mm of rain in three hours;
A product with a rating of 5 protects the user from a storm, i.e. 1.8 cm of water in four hours.

Your jacket’s ability to protect you from the rain will therefore depend on its rating. A jacket model with a rating of 2 is obviously "no worse" than another model with a rating of 5. The two jackets will just meet different needs depending on the weather conditions you encounter.

You'll find these ratings in the technical benefits given on the descriptions of our waterproof jackets on Decathlon.co.uk

These ratings apply to all types of waterproof jacket: from the lightweight, short jacket for the mid-season to the parka that will keep you dry and warm in winter. If you're on the fence between a parka and a jacket, here are two articles to help you choose the one that best suits your needs:

Did you know...? Padded jackets are not rain jackets

The overwhelming majority of padded jackets are water-repellent. And yes, even a padded jacket made from material with a slightly satin finish and fitted with a hood won't keep you dry. We advise you to pack a light, waterproof, compact jacket in your backpack, so you don't get caught out by a downpour! If the lining of your padded jacket gets wet, it won't keep you warm. Alternatively, you can opt for a 3-in-1 jacket and combine warmth, comfort and waterproofing, while still having choice and style.

Find out more about how materials are tested for waterproofing. You'll also know how important it is to test the entire waterproof jacket: the importance of assembly and zips, etc. You also know how to decipher measurements in Schmerber (well done, and it's not easy to do, either at scrabble or at a party). In short, your waterproof jacket should hold no secrets for you! So, are you feeling up to <link href="/contents/b2ecd19a-25d0-4866-adac-f6b22f4e9175" target="_blank">trekking in the rain</link>?

Pénélope

An enthusiast hiker and Quechua employee

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