What Makes a Hardshell Waterproof?

May 12, 2023

When it comes to outdoor gear, having a waterproof hardshell is essential for staying dry in wet conditions. But what makes a hardshell waterproof? In this article, we'll explore key components of a waterproof hardshell & how they work. 

Seam Taping

Seam taping is the process of sealing the seams on a hardshell to prevent water from seeping through. The seams on a hardshell are the areas where two pieces of fabric are sewn and joined together, and they are typically the weakest point when it comes to waterproofing.


To seam tape a hardshell, a thin strip of waterproof tape is applied over the seam. The tape is then heated and pressure is applied to create a watertight seal. This process is often referred to as "heat sealing" or "welding."


It's important to note that not all hardshells are seam taped. Some lower-end models may have unsealed seams, which can lead to water seeping through. If you're planning to use your hardshell in wet conditions, it's important to look for a model with fully seam-taped construction.

3-Layer Fabric

The other key component of a waterproof hardshell is the fabric itself. High-quality hardshells are typically made with 3-layer fabric, which consists of three layers:

1. A protective shell layer: This layer provides durability and protects the waterproof membrane from damage.


3. A waterproof/breathable membrane: This layer is the heart of the hardshell's waterproofing. It prevents water from penetrating the fabric while also allowing sweat and moisture to escape.


3. A liner: Often this layer is overlooked. It sits against your skin and helps wick moisture away from your body and should also have a quality handfeel. 

The 3-layer construction of a hardshell fabric provides both waterproofing and breathability. The membrane prevents water from entering the jacket, while the lining helps wick away sweat and moisture to keep you dry from the inside out.


When shopping for a hardshell, look for models with high-quality 3-layer fabric. Cheaper hardshells may be made with 2-layer fabric.

What is 20k/20k waterproofing?

The 20k/20k rating refers to the level of waterproofness and breathability of the fabric used in the construction of waterproof apparel, such as jackets and pants. The rating is determined by a test called the "Waterproofness Test," which measures the amount of water that can pass through a piece of fabric in a set amount of time.

The first number, 20k, refers to the waterproofness rating of the fabric, which is measured in millimeters. Specifically, it means that the fabric can withstand a water column of 20,000 millimeters before it starts to leak. This rating is considered extremely waterproof and is suitable for heavy rain and snow.

The second number, 20k, refers to the breathability rating of the fabric, which is also measured in grams per square meter per 24 hours. It means that the fabric can allow 20,000 grams of water vapor to pass through it per square meter of fabric in a 24-hour period. This rating is considered highly breathable and can prevent the wearer from feeling clammy or sweaty inside the jacket.

In summary, the 20k/20k rating for waterproof apparel means that the fabric is highly waterproof and highly breathable, making it suitable for use in extreme weather conditions. Typically ratings range from lowest performance at 3k/3k up to highest performance 20k/20k.

YKK Waterproof Vislon Zippers

YKK Waterproof Vislon zippers are a high-quality and reliable zipper option for outdoor gear that requires waterproofing. They are made from durable materials and feature a unique design that provides a watertight seal to keep water out.

The Waterproof Vislon zipper is made from a type of plastic called polyurethane, which is highly water-resistant and durable. This type of zipper is designed to keep water out and prevent leaks, making it ideal for use in outdoor gear, such as jackets, pants, and backpacks.

The Vislon zipper design features interlocking plastic teeth that are molded onto the zipper tape. This design creates a watertight seal that prevents water from entering through the zipper teeth. Additionally, the Vislon zipper features a polyurethane coating on the zipper tape, which further enhances its waterproofing ability.

The YKK Waterproof Vislon zipper is known for its smooth and reliable operation, even in wet and dirty conditions. The zipper is also lightweight and flexible, which makes it suitable for use in a wide range of applications.