Mountain Clothing Basics - How to Choose a Baselayer

A baselayer is the foundation of your layering system, often under-appreciated and uncelebrated by social media but an incredibly important component of mountain clothing.baselayer A good baselayer should feel like a second skin and move with you as you sweat and stretch, while keeping you warm and dry. It is the only layer that touches your skin, and must be made of a breathable fabric that can quickly absorb and evaporate sweat. It also needs to dry quickly as a wet baselayer will feel cold and can lead to irritation, not to mention bad odors.

During high-intensity activities your core heat can generate more perspiration than usual, so it’s important to get the best possible moisture management from your baselayers. Synthetic base layers are the go-to choice for this, able to efficiently wick away moisture and dry rapidly. They can also be durable and easy to care for, meaning they can withstand rough treatment and repeated washings.

Natural fibres are another popular choice, particularly merino wool. These are soft against the skin, incredibly comfortable and offer superb thermo-regulation and odour control. Wool is also a good choice for extended wear and varying weather and intensity levels, as it offers a great balance between insulation and breathability.

A common mistake people make is choosing a baselayer that’s too baggy or loose. Baselayers should fit closely to the body, feeling like a second skin. They should be snug without being too tight, as this is how they’ll keep your body warm and regulated. If they’re too big, they won’t wick moisture well, leaving you with wet, heavy and clingy clothing that will leave your body cold and uncomfortable.

The thickness and density of the base layer fabric is another key consideration. This refers to how insulating it will be, with thicker fabrics offering more insulation and lighter fabrics being less bulky. The temperature and conditions you’ll be working in will also have a role to play, as you’ll need a higher-density baselayer for colder environments than a warmer one.

You should also consider the elasticity of your baselayers. This relates to how much it stretches as you move. An elasticated baselayer is more likely to be able to follow the shape of your body and won’t ride up as easily or become itchy when you move around. It’s also more likely to stay in place if you twist or fold your arms or legs while you’re active.

A good baselayer should be comfortable and move with you, allowing for full freedom of movement. It should be able to flex with your body as you bend, stretch and twist, while staying securely in place, so it doesn’t chafe during your activity. The material should also be soft on the skin and have no irritating protruding seams.

All of Icebreaker’s baselayers are made of breathable fabrics with flatlock seams to prevent chafing. We use a range of materials, from ultralight to midweight to heavyweight. Each fabric has been carefully considered and tested, with our lightweight HH Dry fabric being our benchmark for performance. Its unique manufacturing process, which resembles blowing up a water balloon to release molten polypropylene, results in a smoother fibre that wicks and breathes more effectively than any other synthetic fabric available. This means that nasty odours have nowhere to hide, so it will keep you fresh and smelling great throughout your adventure.