The techniques used in building dry stone walls can be applied during the construction of a number of trail features, including water bars, steps, armoring, and crib walls.
By guest blogger Peter Welch, president of The Stone Trust. Illustrations by Brian Post, executive director of The Stone Trust.
In the rocky Northeast, building a solid trail structure using the materials right at hand is definitely a possibility—if you follow the rules.
First off, it’s unlikely that perfectly flat, squared off stones will be right where you need them. That’s OK though, because building with stone is about using the correct principles and what you have on hand. Building with stone is a problem-solving exercise; as we like to say on the job, “The stones aren’t going to move themselves.”
Before we get started, a quick safety reminder:
• Take care of yourself and others working with you—don’t throw stones, and keep a neat and tidy work area.
• Sturdy shoes, clothing, gloves, and eye protection are very important to the stone mason—they should be for you, too.
• Lift with your knees, not your back. Roll materials if necessary. Building is not a contest of strength, it is a contest of wit and smarts.
• Take your time to stretch and breathe when you are building. Standing up and looking around every now and again is helpful to keep from getting frustrated. Drink water!
Now, let’s get going!
1. Keep Stones Level
Walls for trail building should be built so that the stones and courses (layers of stones), are level. Stones should be level both into the core of the wall and along the face (visible side of the wall). Stones that are not level will tend to slide, causing internal stress in the wall and eventually leading to structure failure as the wall shifts over time. This rule is especially important when building on sloping ground. When setting down the first course of stones, you can dig into the ground to adjust the height of the stones. Also, this first course is where you will want to use the largest stones.
2. Set the Length of the Stone into the Wall
Setting the length of a stone into a wall means placing it so the end of the stone is the part visible in the final wall. In other words, the length of each stone is perpendicular to the direction of the wallThink about how firewood is stacked, with each piece perpendicular to the overall direction of the stack, so all you see are the ends of the pieces. A stone wall should be built the same way.
“Trace walling” or “face walling” refers to placing stones with sides visible. When stones are placed this way, the resulting wall is much weaker.
The following diagram shows a course in two walls viewed from above. The correctly built, “ends out” wall is on the left; the wall on the right is built incorrectly with the stones’ sides facing out.
3. Build with the Plane of the Wall
To build with the plane means to align the stones so that the faces of the wall are even. String lines are especially useful in keeping an even plane to the wall. Use taught strings to create a guide that you can line up the stones to. The outer most “bump” of each stone is what should be in-line. By building with this in mind, the wall will look smooth and even when finished. This applies when examining both the cross-section and top view in each course, as seen in the diagram below.
4. Heart the Wall Tightly
The wall should be built as solid as possible. Gaps in the interior of the wall, between the face stones, should be tightly filled with small stones. The tighter the hearting , as these small stones are called, the stronger the wall.
Hearting takes place as the wall is being built. It is important to make sure each course is completely hearted before beginning the next course. Fewer, larger hearting stones are much stronger than many small stones. Anything that can be easily shoveled is too small to use for hearting—and absolutely no concrete or soil should be used! Hearting stones are much more effective if they are flat or angular. Rounded stones tend to act like ball bearings. Hearting stones should be placed individually, not randomly thrown into the wall.
Not properly hearting a wall allows stones to move independently of one another, resulting in a structurally weak wall that will not last.
5. Two Over One and One Over Two
Once you have set the first course of stones and completed the hearting, you are ready to build the next course.
“One over two” means that each stone crosses a joint below, so that it is sitting on two stones below it. What should not be done is stacking stones in a manner that creates vertical joints running from one course to the next. Walls with running joints are not only very weak, they look bad.
In the diagram below, the face of two walls is shown. The correctly built wall, with the “one over two” principle applied, is on the left; you can see the vertical joints running up the incorrectly built wall on the right.
So there you go! These are the basic rules of walling, which will help you create strong, beautiful stone walls.
To learn even more about dry stone walling, we’d love for you to join us during the Trail Conference’s first-ever dry stone wall workshops, taking place April 15-17 and May 28-30 at Trail Conference Headquarters in Mahwah, N.J. Three instructors from The Stone Trust will be teaching dry stone walling techniques as we build a wall in front of the new headquarters building at the historic Darlington Schoolhouse. For more information and to sign up, visit www.thestonetrust.org.
Happy trail building!