Building a Rock Wall | Ask the Expert
In the middle of the 19th century, when America was still a farming nation, more than 250,000 miles of stone walls coursed through New England and New York. Over the last 40 years, starting with his family’s business and now on his own, Kevin Gardner has rebuilt some of that old fencing. “For me,” he says, “the old walls are connected to an explicit former world that looked, felt, and operated very differently from our own.” The work isn’t easy, of course, but if you’ve got the patience, a strong back, and a few key tools (a spade and a couple of iron bars), Gardner says, it’s doable.
The Right Stuff
Good material isn’t cheap; a pallet of weathered granite can cost as much as $800. But there’s another option: Owners of woods where old crumbling walls reside, out of sight, might be willing to sell the stone. (Keep in mind that we’re not advocating stripping existing walls that are sturdy.) “Speak to your local road agent,” Gardner suggests. “He generally knows what the landscape is like,” and can tell you whom to talk to. Another option: Purchase cheaper granite riprap (about $15 a ton) for the interior of the wall, and expensive stuff for the facing.
Good Ground Game
Prepare the ground by digging a hole with the spade. If you’re rock-free, keep digging to create a trench to run under the length of your eventual wall. Make it 1.5 feet deep and fill it with crushed granite. This will give your wall a sturdy base. “An enemy of walls is their own weight,” Gardner explains. “It compresses the ground beneath relentlessly over time.” If the ground is already strewn with rocks, skip the trench. “The ground won’t compress that much,” Gardner notes.
A wall’s stability comes from its first layer of stone. Gardner says a good rule to follow is one in which the width of the retainer is three-quarters the height of the wall. If the structure is 6 feet tall, for example, the bottom layer of rock should extend out 4 feet. “I once worked on an old carriage house where the foundation walls were 8 feet high but their ‘footprint’ at the base was 12 feet wide,” Gardner says.
The Right Fit
Too often, Gardner adds, novice builders pay too much attention to the individual stones and not the rock wall as a whole. “They look for beautiful stones and then lug them around trying to find a spot for them,” he says. Instead, look at what the wall needs and find stones to fit those areas. “It’s a matter of becoming more attuned to what your materials will do and staying patient,” Gardner advises.
A sturdy wall, Gardner says, is one in which “the independent stones are not dependent on just one other stone to hold their position.” To enhance stability, builders incorporate the two-over-one/one-over-two practice, which caps the seam between two rocks with another stone above it. Long seams running up or across the wall, Gardner adds, weaken the structure’s strength significantly.
One simple method for keeping your wall straight and looking level is to build within a defined area marked by stakes and string. Another, and Gardner’s favorite, is to use an element of the surrounding landscape–such as the clapboard lines of a house–as a visual reference. “That means that in the end, even if it’s not dead level to an instrument, it looks level,” Gardner explains. “In the end, it matters how it appears, not what it is.”