Design and Build Your Own Dry-stack Rock Wall

Ken M. Gregory

For gardening beauty and ease of cultivar maintenance, few projects make such a great addition to your perennial collection as a rock retaining wall.

Whether you're planning on doing it by yourself, recruiting friends and family to help or planning on hiring out the work, now is a good time to dream and design your garden retaining wall. If you have the strength and health to dig the soil and then place the rocks, you will have not only the beauty of the project, but the pleasure of the hard work. Even if you have the dream and then hire the help from others, you will enjoy these walls almost as much during construction as you will for years to come.

While you may think of winter as indoor time, there are so many days when you need to get outside and dream of spring and maybe work a while during the warm part of the day. A perfect project during these winter months is to walk around and consider a dry-stack, rock, retaining wall. Is there a slope somewhere in your yard where the light would be good for a perennial garden? Is there an unused part of the yard that would make a good addition to your landscape but for the slope? Then you have the beginning of a dream and next you have the opportunity to work on that dream.

As you start the plan, consider the function of the wall. I'm recommending a retaining wall because a rock wall without a clear function feels out of place and awkward in a landscape. We've all seen a perennial collection surrounded by a circle of stones. Someow, it looks "wrong." The rocks serve no more purpose than "top stitching" around the flowers. The effect tends to be cheap and unattractive. If all you're doing is outlining the flower garden, then a simple and clean cut edge in the grass delineating the transition from lawn to mulched garden would be better. Without a function, rocks seem awkward and forced into the landscape.

However when you study the topography of your yard and dream about gardening, all but the flattest of locations have some gently sloping area that could be improved with a small retaining wall. Such an addition may be what your landscape requires as part of an overall landscape design.

Once you've identified the place for your rock wall project, it's time to visualize the layout. With a bright orange extension cord, a length of rope or the trusty garden hose, lay the outline of the wall down onto the ground. This is the time to experiment. Try it here and there. Look for function that might not be obvious at first. Could your wall terrace the yard changing an unused slope into two distinct levels? Could the area at the top or bottom of the wall feature a garden as prime cultivar display area? Could your wall, perhaps, as in Illustration One, serve multiple functions? This wall is expanding an area beside the drive creating an additional parking space at the same time as it's creating a special garden display area for daylilies, hostas and irises.

As you can see in Illustration One, once you've identified the slope needing to be terraced and traced the outline in the grass, you must consider the consequences of the project before you begin the cut. Will the drainage work or will it erode the wall? Are there tree roots that are in the area and should not be damaged? Are there utilities to be taken into account? Illustration One shows several aspects of the project. On the left side, you see the cut down through mulch and dirt to a new level which will be the base of the wall. For the cutting through the dirt, think like you're shaving the ground more than excavating it. Using a mattock and a flat shovel, slowly peel away the soil. I've found that this works best in winter or early spring. The digging is cooler and more importantly the ground is workable. Unlike the hardpan soil of July, in December or March it's more like sculpting than digging. Step back from the cut and look at it from different angles. Does it look like it belongs in the landscape? Usually this step will evolve the project into a more pleasing cut with clear and appropriate lines that flow and relate clearly to gravity and contour.

Take your time and enjoy it. I am amazed at the number of people who observe me on a digging project. They often think that digging and hauling dirt and rock are burdens to be avoided. I still have enough child in me to enjoy playing in the dirt. And my Dutch ancestors must have past down a need to dig and trench through the earth like a human mole. The preparation of the wall can take weeks of pleasurable effort as you dig and refine the shape during available times and good weather. You would be wise to cover the area with some anchored plastic over the course of the project so that a storm does not erode the sides of the excavation and require more digging than you'd planned.

With your rock wall planning and construction, don't forget the concept of "level." A wall can quickly loose its functional appearance when the terrace looks more like a slippery slope. Make sure that the base is level and you'll enjoy years of gardening on the terrace and it will look "correct." If your landscape has more than a couple of levels in an area, consider two smaller terraced walls instead of on great big one. The construction will be easier and the two walls will work together with a commonality of design that will further unify your garden landscape.

In Illustration Two, you can see that your rocks do not have to be identical to make an attractive wall but they do need to be similar. While some are much larger than others, the wall looks unified in design because all of the rocks have a similar texture and coloring. This commonality of materials is what holds the design together in the single rock wall, your larger landscape and even a community. If you've already used brick in your home and landscape and flagstone paths in your garden, be careful about introducing another material into your design. It can get "busy."

Think of your wall as the skeleton or structure for your garden and not the final emphasis. Soon the wall will be draped with vines and plantings and it will fade from dominance to a complementing component of your garden. It will blend into the garden design and after a season or two look it will look like it's been there for years, anchoring your garden into a natural part of your yard and into the years to follow.

In Illustration Two, you see how a curvelinear wall design can incorporate a sharp angle. While the 90 degree turn in the wall could look abrupt and out of place, it works here because it serves the function of the area -- cars park better in rectangular areas rather than circular areas. The angle complements the curves in the wall at the same time as it gives the wall a strong visual emphasis. It also makes the wall stronger.

Also in Illustration Two, you can see the "deadman" concept of dry-stack wall construction. This kind of wall is not mortared but tied into the earth with overlapping seams and frequent "deadmen," rocks stacked during the construction and turned into the hill so that the weight of the backfill locks the wall into place. This isn't a rigid wall like one you would find with mortar. Rather it breaths with the cycles of the seasons. It weeps moisture gently throughout the length of the wall and expands and contracts with the freezing and thawing rather than resisting movement until it cracks like a mortared wall. You do want to slightly tilt your wall back into the hill as you build and backfill it so that this annual expansion and contraction does not topple over the wall. All in all, your dry-stacked wall can be every bit as long lasting as the neighbor's mortar wall and much more interesting. Look at stone walls in New England made from rocks removed from farmers' fields. Examine the amazing "slave walls" of stacked rock in Tenessee that stand today. Consider the stacked rock walls of Ireland that have lasted centuries.

Illustration Three shows a finished portion of the wall. As I've taught people to build these types of walls, I've noticed that most people mistakenly look at the back of the wall as they stack it rather than the front. As you place a rock down, look over it to see that you have the flattest surface of each rock facing the front of the wall. It doesn't matter how the back of the wall looks once you've backfilled it. You should backfill it as you construct each layer and then tap each rock into the wall to give a uniform flat fontal appearance. Also, don't be cheap with your rocks since stretching the rocks will critically weaken the wall. Not only do you turn occasional long rocks into the hill as deadmen, you should also lay the rocks heavy and flat. Too often I've seen these walls collapse for people who have tried to stretch the rocks over a larger area. Never turn a thin large rock on its side since this will look good for awhile but make a seriously weak spot in your wall which will need re-construction later.

Functional rock walls have served so many purposes and yours will too. In Illustration Four, you see the space under a deck transformed into a useable garden tool room. Where there was a typical slope off the deck, I dug out a walkway that connected a lower yard area to an upper section and also accessed the new area I dug out under the deck. After stacking the rocks, I closed in beneath the deck and the owner had a perfect place to store garden tools and equipment. And the gentle slopes along the new rock walls make easy egress with the mower or wheelbarrow from yard to storage. This kind of change to a landscape not only adds beauty, but the functional improvement greatly enhances the value of the home, something any homeowner and neighbors should appreciate.

All along this meandering walk from lower yard to the upper yard, you have gardening at waist level. You can plant, weed, mulch and admire the bloom without bending. In this case, a separate and awkward rose garden in one part of the yard was redesigned into a year-round perennial garden and worked into an overall unified landscape design with obvious improvement. Where there was visual division and a feeling of separate and unrelated gardens before, now there is much easier access between related garden areas AND new storage space is created right where it was needed.

Many people shy away from building a rock wall, but it can be great way to exercise and improve your garden landscape. For simple wall construction techniques, I recommend John Vivian's Building Stone Walls. And for great design ideas for your rock wall projects, I recommend Jan Whitner's Stonescaping.

It is a great time of year for this kind of gardening project. Your garden landscape should be a four-season experience in color, texture and form. Stacked rock walls will do much to augment your garden's transition from a summer garden into something you'll find pleasure in through heat and cold, from spring bloom to winter berries.

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