In the most general sense, a base layer is a piece of clothing that is worn against the skin. So a base layer can be a tee shirt, a long sleeve shirt, or leggings on the bottom. For the purposes of this article, when we say base layer, we mean the top you will hike in.

How do I select base layers for climbing Kilimanjaro?

A base layer is integral to staying comfortable on the mountain. They come in all shapes and sizes. For Kilimanjaro, you should bring three (or more) for your climb. This is what our gear list includes for shirts:

3 – Long Sleeve Shirt
1 – Short Sleeve Shirt

The purpose of the hiking shirt is threefold – to protect the body, to provide warmth, and most importantly, to keep the body dry by wicking moisture away from the skin.

Base layers are a very significant part of your gear because they are in direct contact with your body. It needs to function well and feel comfortable through changing outdoor conditions. A poor choice of base layer can lead to chaffing or rubbing. Even worse, it can lead to hypothermia if you have a fabric that won’t insulate.

Base Layer Material

So let’s first discuss what types of fabrics you should look for. The most common materials for a baselayer are polyester/polyester blends and merino wool.

Polyester and polyester blends are synthetic base layers. These fabrics are known for their excellent moisture-wicking abilities. The fibers have hydrophobic qualities, making them water-repellent, and they also dry very fast. Polyester fibers are lightweight, strong and durable. They have excellent wear and abrasion resistance. Finally, polyester shirts are very affordable depending on the brand.

Merino wool is a fine, soft wool that is warm and handles moisture well. It is not like regular wool that can be scratchy and uncomfortable. Merino wool is an ideal fabric for hiking shirts because it’s highly breathable, insulates even when wet, dries quickly, and is naturally odor-resistant. The downside is that it is expensive. The smaller the diameter of the wool fiber, the softer it is and the higher the price.

Cotton is a no-no when it comes to hiking clothes. It is super absorbent but dries very slowly, making it unsuitable for use in an outdoor environment. Cotton does not fulfill the fundamental role of a baselayer. It absorbs the moisture from the body, but does not transfer it. Therefore it does not have insulating properties when wet. Instead it holds the moisture in its fibers, against the user’s skin. Wearing cotton will make you colder because of the constant contact with your own sweat.

Base Layer Weight

Base layers come in different weights, or thicknesses: lightweight, midweight, heavyweight, and expedition weight. Each will provide different levels of insulation and moisture wicking. As a rule, the thinner the fabric, the better it wicks and the faster it dries. Most people will prefer a light layer because of this, even if it is not as warm. And that’s what we would recommend for climbing Kilimanjaro – lightweight base layers.

Lightweight base layers also have more versatility than medium, heavy, and expedition weight clothing. It is far better to have lightweight base layers that are comfortable to wear in warm weather, that you can add layers to when it gets cold, than to have heavyweight base layers that are too hot for day to day trekking.

Base Layer Features

Some common types of base layer tops are crew necks, quarter and half zips and hooded shirts. Though crew necks are pretty standard and will certainly work on the mountain, we do believe that quarter zips, half zips, and hooded shirts have real advantages. Quarter zips and half zips allow you to regulate your temperature by zipping up or down depending on the conditions. Hooded shirts offer the additional benefit of covering the head and neck and we highly recommend them.

Currently in style are “monkey thumbs” – a hole in the sleeve meant for the thumb. These sleeves are cut longer to allow for this and usually extend to the knuckles.

As a general rule, it’s better to be covered. It’s not the best idea to climb Kilimanjaro wearing a tank top, sleeveless shirt, or sport bra and shorts. Being covered protects the body from the sun and weather. That is why we have one short sleeve tee on our gear list but multiple long sleeve tees. You could certainly get by without a short sleeve tee and have more long sleeve tops instead.

Ideally, a base layer top should cover your body as much much as possible. It should be long enough to tuck it in your pants and should fit closely by design. A loose base layer does not work as well. The fabric needs to lay against the skin in order to pick up moisture.

You can find all your outdoor gear at these preferred retailers:

REI, Backcountry, Moosejaw