Stone Walls That Stay Built
A master waller shares how to dry-lay stone walls that hold their ground for centuries.
Synopsis: Brian Post is a Master Craftsman–level waller, certified by the Dry Stone Walling Association of Great Britain. In this article, he explains that stone walls last longer than mortared walls, and describes how to build a dry-laid stone wall. His instructions include making sure to base the design on the site and type of stone, not worrying too much about the foundation or about fitting the face stones tightly together, forming a strong connection with hearting stones, and holding the wall together with capstone and copestones. Post describes the five essential rules of stone walling, and how they can help you build walls that will last centuries.
I began my professional training as a waller working under certified craftsmen in Great Britain, a country whose landscape is laced with stone walls that date back millennia. In New England, where I live, two-century-old walls are common. While this may come as a surprise, that’s far longer than most mortared walls last. If you learn to properly lay dry stone, you can build walls that outlast your great-grandchildren.
Mortar hurts more than it helps. While it can take years of practice to efficiently build a near-perfect wall, building a good dry stone wall is quite easy. The process starts with forgetting what you think you know about the importance of mortar. One reason for their longevity is that properly laid dry stone walls flex as the ground moves, whereas a mortared wall will crack. This flexibility often allows dry stone walls to be built directly on the native soil, while mortared work requires a concrete foundation below the frost line. And while a dry stone wall allows water to pass through harmlessly, mortared walls can trap moisture that will destroy the wall when it freezes. In a dry stone wall, the aim is to use gravity to maximize friction. Friction keeps the stones from sliding apart, and their weight increases the friction. But even the best built wall can fail if it is poorly designed.
Base the design on the site and stone. When siting, think about what can damage a wall. In northern areas, set walls back from roads and driveways so that plows won’t push snow against them. Trees growing in girth can put pressure on walls, and roots can shift or lift when a tree blows in the wind, pushing a wall up from underneath. A good practice is to stay back at least 10 ft. from trees and roads. The foundation is the earth or gravel the stones rest on, and it should be dug so that it is level from side to side. If you are building on a slope with less than a 1-ft. elevation change in 20 ft., just run the wall parallel to the ground. On steeper slopes, dig the foundation in level steps like stairs. Otherwise, the stones will gradually slide downhill and cause the wall to fail.
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