Trail erosion can be an ongoing challenge, depending on a destination’s local terrain and climate conditions. Armoring a trail is a great way to prevent erosion and ensure it will withstand the elements for years to come. Plus, it can add beauty and variety to a trail.
But there’s an art to doing it correctly. Various factors should be taken into consideration, including where to use armoring and which materials to employ.
To learn more about trail armoring, Singletracks spoke with several professional trail builders to gather their opinions on the topic.
What is trail armoring?
Nat Lopes, Owner of Hilride and a professional trail builder with 15 years of project management experience, defines armoring as “any time rock is used to create a more stabilized and durable treadway than can be achieved with the native soils.”
Lopes said that, while sand, gravel, decomposed granite (DG), and other fill materials might be used in armoring projects to create a more durable, well-drained treadway, “armoring” really means rock that is strategically placed and set to lock in position, providing a stabilized tread surface.
Jeremiah Stone describes himself as a nomadic MTB rider, instructor, and builder with a love for two wheels. His company, Unearthed Trails LLC, builds trails around the country. When asked how he would define armoring, he provided a broader definition than Lopes, describing it as “using any material other than dirt to reinforce or support the tread of a trail.”
For David Renko, a senior foreman with Progressive Trail Design who has been building trails for 25 years, armoring can encompass a range of materials. However, he noted that there is a slight difference between armoring and surfacing. “They are synonymous, but the term ‘armoring’ in the trail building industry refers more specifically to rock, concrete, asphalt, or another type of hardened surface. ‘Surfacing’ can be a hardening technique, but, unlike armoring, it can also be a soft surface technique.”
Renko also noted that builders can “harden” a trail by augmenting the soil with a hardening compound, which can turn a soft surface into a hard one. However, hardening is not the same as armoring.
Why is armoring necessary?
According to Lopes, armoring is needed for “trails with challenging terrain conditions that might include low-lying areas with poor drainage, steeper areas with significant slopes, areas with erosive soils, or high-use areas that have constant, heavy year-round use.”
Stone sees armoring as necessary “when I know an area of trail will be prone to drainage or erosion issues.” He believes it presents a much more resilient and enjoyable feature than some of the other solutions to erosion.
In Renko’s view, armoring is also necessary in places like bike parks, where trails have a high volume of use and need to remain consistent throughout the riding season. Armoring trails in those areas also helps reduce the need for trail maintenance.
When should armoring be used?
“Armoring should be used based on the best practices of impact, safety, and sustainability,” says Renko. In addition, factors such as the client’s wishes and the user experience should be considered when deciding whether to armor a trail.
Stone loves seeing a drain or low crossing where rocks have been placed well and locked together like a jigsaw puzzle. “It’s important to me that none of them move, because I want them to do their jobs as well as be safe for riders. If the rear tire catches the edge of a loose rock just right, it can flip on end and act like a pole vault to the rear wheel. If the rock moves and comes out, it leaves a hole and can be, at best, a flow killer and, at worst, a wheel trap. A section of rocks half buried in a trouble spot on the trail can also reinforce the surface and keep it from becoming a bog.”
Armoring is also a good way to reinforce features like jump faces and berms, according to Stone. “I love seeing jump faces that are rock armored. When done well, it makes for a super consistent face/lip that will hold up over time. I’m also a fan of armored berms. They’re hard to build right, but they look awesome and can be fun to ride.”
Trails can be made durable enough for year-round riding by using rock to raise trail treads above surrounding grades, to harden the trail tread itself, or to ford over smaller drainages, creeks, and streams. “While the armoring can be expensive, especially if the rock needs to be imported, and is extremely labor intensive, the investment will allow more users to use the trails in a wider range of conditions and for most of the year, with less maintenance, and most importantly with less impact to the surrounding environment,” said Lopes.
Some methods of armoring are better than others
“My absolute least favorite armoring is the standard low-effort water bar,” said Stone. “Done poorly, these can be rim killers and super disruptive to a ride. They can kill the flow and even be hazardous depending on the angle of the rock in relation to the tread.” He also stated that he’s not a big fan of using man-made materials, such as concrete or landscaping bricks. “I’ve seen it done well and enjoyed riding it, but I think other materials look better.”
Additionally, Stone said that trail builders should use the appropriate armoring material for the region in which they are building. “In places that have limestone, you can’t trust the grip on the rocks — especially when wet. In those cases, you want to keep the armoring distance short and straight, making sure riders hit the seams perpendicular and don’t have to corner on the slick surface. In other places with sandstone and granite, you can do all kinds of things since you can trust the traction and grip.”
Adding rock work when it is not necessary or does not fit with the nature of the trail, the terrain, or the environment can break the flow of the trail or even defeat the purpose of the armoring itself. “If the rock armoring creates safety issues or pushes users off trail looking for smoother or faster lines, then there’s no point to having it,” said Lopes.
Using stonework is very rewarding for Renko because it lasts for ages and is the slowest-moving method of armoring. “I enjoy harvesting materials from the land and applying it to the trail because it feels like they fit and belong there. It gives the appearance that the trail has been there forever.”
Renko cautioned that trail builders should carefully examine the trail location before armoring, considering whether material is sloughing off the trail or onto it. He also said that consideration should be given to whether foreign materials should be introduced to the environment and what impact they could have on it.
Done right, armoring can bring variety and fun to a trail
“Armoring done well can be a great way to manufacture some technicality in a trail,” said Stone. “A good machine builder can frame some support boulders and puzzle together some rocks in the tread to make things more interesting.”
Lopes said that armoring trails with rock is a great solution for challenging terrain conditions. “There are many different ways to armor a trail with rock to make them more sustainable, beautiful, and enjoyable.”
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