What makes harnesses strong enough to keep us safe? And durable enough to stand up to the rigors of climbing indoors and out? Or why do some harnesses last longer than others? It all comes down to the materials used. Below, we dig into the soft and hard goods that most manufacturers use to construct climbing harnesses, and how they come together to hold us high off the ground. No matter the construction, all CE / UIAA certified harnesses are safe to climb with when used as designed.
Nerd Alert: In this post you’ll learn about the pros and cons of different materials (in various circumstances) but it is less about how to choose a harness and more ‘isn’t it wild how harnesses are made?!’. Many of the details below are minute and could be hard (or impossible) to identify in your current (or future) harness since the brands don’t list these details in the technical specifications.
Harness Webbing
Though we don’t always see it, the material that makes up the bulk of the harness strength and support is the webbing. Webbing is the material that provides the strong and flexible backbone of a harness and ties together all of the weight bearing parts, including the belt, the leg loops, and the belay loop.
Traditionally webbing has been made from nylon or polyester. Though both materials have been around and used in harness and safety equipment construction for a long time, they each have some advantages that dictate where most brands tend to use them in harness construction.
Nylon Webbing
The most common soft material in all of climbing is Nylon. For Webbing, Nylon is the heaviest option and it is slightly more susceptible to UV and water damage than Polyesters. It is however significantly stronger than any other option with some forms able to withstand as much as 12,000+ pounds. Nylon is also quite slippery, making it abrasion resistant and an ideal choice for things that see intermittent rubbing while under tension, like our belt and leg loops.
Brands use a couple of different widths of Nylon webbing in harness manufacturing. The type we see most on adjustable straps is usually 1″ wide tubular webbing which is woven in a tube shape and flattened. Unlike flat-woven webbing like you might see on backpack straps, this method of weaving gives it the ability to share load across the entire width when it is tightened and dragged across things like rock surfaces. This is the main reason it is often chosen for buckle-adjustable harness parts. Some brands still use flat webbing in these applications, though it is usually a much thicker weave to give it that extra durability.
You will also see 2-3″ webbing used in waist belts on some sit harnesses or as the main structure in most full body harnesses. This form factor allows for pressure to be spread across a wider area, which can be particularly helpful in adding comfort to the parts that hold most of our weight or on unpadded leg loops. This wider webbing is flat woven in a pattern and similar to the stuff used to make car seat belts. The massive amount of nylon used makes it heavy, but super strong (in the 20,000 pound range).
Polyester Webbing
Because it is less stretchy and doesn’t absorb as much force, PolyEster (PE) is not quite as strong as Nylon, though it can still be made to hold upwards of 5,000 lbs. It is highly UV and water resistant and is more resistant to heat with a super high melting point of 275ºF (135ºC). When soft goods rub on each other it creates heat from friction, which weakens the polymers and eventually causes them to melt rather than to cut or snap like you might think. Because of this resistance to heat from friction, we often see PE used in areas where soft materials come in contact with each other, such as the reinforced tie-in loops that join the waist and leg loops to the belay loop.
Polyester webbing used in harnesses is typically flat woven which makes it more flexible and pliable, so it is a common choice for the protective outside edging on waist belts and leg loops. It is also commonly used as flexible internal structure in gear loops that have plastics molded or fed around them for durability and shape.
Ultra High Molecular Weight Polyethylene (UHMWPE)– aka Dyneema
A material that is becoming more and more common in harnesses is UHMWPE– most often called by one of its brand names, Dyneema®. Dyneema is one of the wildest materials humans have made. It is stronger than most steels, lighter than nylon, chemically inert, odorless, tasteless, non-toxic, is as slippery as Teflon® (due to the fact that it self lubricates? what?); it ALSO floats on water. Add all that up and you can start to see how it can be an attractive material to use in climbing applications, especially when you need strength, low weight, and high resistance to abrasion.
Dyneema is being used to make webbing in the same ways as nylon and PE, but because of the added strength, much less material is needed. This actually creates a bit of a problem, because thin materials around our waist and legs can be very uncomfortable. To combat this, brands are getting creative in construction methods such as using multiple strands of webbing to help spread the load, or even experimenting with making super thin mesh weaves of Dyneema that essentially function like very wide webbing, but at a fraction of the weight and bulk.
Because of its properties it is difficult to dye Dyneema so you can usually notice it easily in stark white. It is also really tough to sew to itself, so most brands use polyester thread combined with heat lamination and creative stitching patterns to keep it in place. All of the nuance required to work with Dyneema makes it quite pricey when compared to Nylon and PE, so harnesses that use lots of Dyneema are usually on the higher end of the price range.
Fabrics in Harnesses
The parts that make up the largest bulk of most harnesses fall into the category of fabrics. These usually include the inner and outer shells of the waist or leg loops on sit harnesses, and while they add structure and comfort, tend not to do much of the weight-bearing that webbing does. Much like webbing, there are a handful of types of materials used in the fabrics that cover our harnesses.
The Outsides
Nylon is a particularly good choice for woven fabrics that cover the external parts of leg loops and belts due to its abrasion resistance. As a woven fabric, nylon can be made with all kinds of properties like specific stiffness or abrasion resistant patterns, and because it is easily dyed, it will often be the most colorful parts of a harness. Its stretchy nature also adds a bit of give to a harness, so you’ll see it paired often with polyester in places to reduce stretch and add structure, such as the piping along harness edges we mentioned earlier.
For areas of super high wear or on higher end harnesses, brands can opt for even more rugged versions of material called laminates. These are essentially a base nylon fabric with a heated-on or coated micro-surface that makes them more uniform, less porous, and tougher. Think of it like ironing on a bit of extra armor. Most commonly used are TPU and PVC plastics which are essentially nylon and polyester, respectively, though there are more and more brands dabbling in fusing or weaving Dyneema into fabrics for all those wonderful science-y properties mentioned earlier. These fabrics are akin to what you would see on the outsides of backpacks and tents, and are mainly in place to take the bulk of the wear and tear your harness will see in contact with rocks and gear.
Most entry level harnesses opt for cheaper, easier to make external construction like basic Nylons, which are plenty fine and can last well when well cared for. Brands tend to reserve the techy science-stuff of laminates or combining laminates and nylons for more expensive models that are made to handle more technical and abusive climbing endeavors.
The Insides
When it comes to the human-facing side of our harnesses (inside the leg loops and waist belts), we tend to like things a bit more flexible than tent materials against our bodies, and this is where knits come in. If you’ve worn any athletic clothing in the past 30 years, chances are you have encountered knits. They wear nicely against skin, do a good job of wicking moisture or sweat, and can be made in all the fun colors. The insides of our leg loops and belts are lined with knit to keep our bodies dry and comfortable.
It is also common for brands to use layers of knitted mesh alongside or even over the top of standard knits to aid in moisture dispersion and airflow. Mesh lets a lot more air through than a standard knit to help you stay dry. If you find your harness feeling a bit too warm at times, look into one with more mesh in the belt and leg loops.
Another textile used a lot in harnesses is elastic. Elastic is used everywhere on harnesses that we need a bit of flexibility while keeping things comfy and in place. Mostly you will notice it in the risers that hang the back of your leg loops. It is also found along belts and leg loops near the buckles for a storage solution for excess tails of webbing. If you have a fixed leg loop harness, chances are elastic is in use near the tie in points to give a little stretch for flexing muscles and fluctuating weight and clothing thickness.
Foam Padding
Most harnesses use one of two types of foam, placed between the inner and outer layers of fabric. This foam provides the much appreciated padding in key places around the waist belt and the leg loops.
EPE (expanded polyethylene) foam is the same stuff used in lightweight packing materials and pool noodles. It is super light, extremely inexpensive, easy to work and cut and can be made from partially or fully recycled materials. Its open cell construction keeps it light and spongey, but this also means that there is a lot of air in it that can crush and crease over time more quickly than denser closed cell foams like EVA. Many brands use stacks of thinner EPE foam to dial in shape or support in key places, which helps combat the squish factor but will often make for a bulkier harness.
EVA (ethylene-vinyl acetate) foam is nearly 5 times as dense as EPE and considerably stiffer and more durable while being marginally more expensive. If you have worn flip-flops or Crocs, that’s EVA. EVA’s density provides a much stiffer support that lasts longer in harnesses, and gives it the ability to be laser carved and molded to certain shapes in a way that EPE cannot. These carved out spots allow for a trimmer fit and reduced areas of pressure where the webbing wraps through, resulting in a much more comfortable fit over the life of the harness. One of the big differences in higher-end models of harnesses is the choice of EVA foams over EPE, though this shaping and molding does make them more expensive than traditional EPE.
Stitching it All Together
While polyester is used in key places like edge finishing and abrasion protection, the bulk of PE in harnesses is responsible for stitching and sewing. Thanks to its slightly stiffer nature and resistance to stretch, it provides extra structure and ensures that certain parts of your harness stay strong and stay put. That stiffness in your belay loop comes from continuously wrapped PE stitching over multiple layers of webbing.
Having webbing that is strong enough to hold you only matters if that strength is maintained where everything gets joined together. Brands use various stitching methods and yards and yards of thread (sometimes several yards in a single stitch!) to make sure that a harness can hold weight and pass certification.
We’ve also been told that Polyester is the easiest thread to work with when sewing several different types of materials together at once because it isn’t too slippery or too grabby, and has a good amount of friction for feeding and threading well in industrial sewing machines.
Buckles
Today the vast majority of climbing harnesses use aluminum buckles, although a few still use steel buckles. Though the shapes vary wildly from brand to brand, they all perform the same end goal of securing the webbing of our waist and leg loops so they can’t come undone. Aluminum is extremely strong for this task and very light weight, inexpensive, and long wearing. Most aluminum buckles are anodized with an attractive color that also makes them more durable as well as easier to find for safety checks.
If you want to go over buckle styles and their pros and cons, check out this post all about buckles.
Overall
Harness designers need to use some of the strongest materials and sewing methods to ensure your harness is strong enough to climb in and take (completely unrealistic) falls in to pass safety CE / UIAA tests and standards.
In the history of climbing it is incredibly rare for a harness to break and in those rare cases, it’s because the materials were completely worn out (obviously so, not subtly so).
In the nerdiest of worlds, it’d be cool if the brands making harnesses posted the materials used so we could actually compare durability or other characteristics. Or it’d be awesome if the brands posted photos of the harness insides, so we could drool over the stitch patterns and all the intricate constructions. Until then, we’ll have to take the word of the marketing copy, reviews, or gear videos that talk about all the details.
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