When looking for an outdoor jacket to protect you from the weather, a key consideration is its ability to keep you dry. A simple desire that raises a great number of questions… Hazel Johnson at Marmot has been so incredibly helpful and has answered HUNDREDS of our questions about Goretex, PFCs, layers, waterproofing etc that we were so honoured when she agreed to write an “Idiots (that’s us not you btw!) Guide to Waterproof Fabric”. Thank you so much Hazel!

With so many different waterproof fabrics available it is possible to spend a small amount of money for a jacket that is “waterproof” which may suit your needs if you are simply dashing between your car and home. If you are however planning to be more active in your chosen jacket, you may want to consider spending more money to get a something that is not only waterproof, but breathable too.

Why does it matter if a jacket is breathable?

In simple terms, a jacket that is breathable will keep you drier and more comfortable as it will allow the moisture that your body creates to escape.

This is not an instant process, and will be more efficient in some fabrics and will also vary depending on the weather conditions that you are experiencing. If the weather is very warm, not only will you create more moisture, but the fabric will be less efficient at moving any moisture created to the outside. All waterproof fabrics work best when the weather is cooler creating a larger temperature difference that helps to pull the moisture through the fabrics.

Another factor that will affect how dry the you feel is the construction of the jacket and what type of fabric is used.

Waterproof fabrics come in 3 key formats.

A 2-layer waterproof fabric will have a membrane (the waterproof bit on the inside) adhered to a face fabric (the outside of the jacket). These fabrics will feel quite sweaty if you are working hard, as your sweat will condense on the inside of the jacket before your body heat helps to push that moisture through the layers of the jacket. To avoid this sweaty feeling, you may find that jackets using this type of waterproof fabric will add a drop liner (additional loose fabric or mesh) to keep the moisture away from the person wearing the jacket.

A 2.5-layer fabric will have a membrane adhered to a face fabric then a print added to the inside of the membrane to help keep the smooth membrane from sticking to the skin of the wearer. Helping the jacket to feel less sweaty whilst keeping the jacket light.

In a 3-layer jacket the membrane is sandwiched between the face fabric and a backer (inner fabric). The backer fabric is normally a woven construction, creating small dips for moisture to collect in without feeling that it is there. Allowing the heat of the wearer to push the moisture through the fabric more efficiently.

A 3-layer construction will be heavier than a 2.5-layer construction, but lighter than a 2-layer with a drop liner.

In addition to how waterproof and how breathable a fabric is, it is also worth considering how durable the fabric is. It is possible to get all the above constructions in varying weights of fabric. The lighter the face fabric, the less durable the product will be. Conversely, the heavier (thicker) the fabric used the more durable the product will be.

In a fully waterproof jacket you should expect for all the seams to be taped (a fabric strip to cover all the stitch holes) to ensure there is no point where the water can work its way into the jacket. You may get some products that are critically taped, meaning that only the key seams will be covered (normally shoulder seams and key side seams).

Which type of jacket is best for the consumer will depend on what activity they are taking part in, along with budget and how important weight and durability are to them.

Hazel has also provided the following PDF to help explain this further – 04_Fabric-Technologies

By Hazel Johnson