By Gordon Hayward

We are blessed with stone that defines our diverse regions: Atlantic coast to Canadian Shield to the Rockies. Gordon Hayward has listened to stone where he builds: His experience offers guidance for our efforts in Canada.

     Stone walls are built in two basic forms: freestanding and retaining. Freestanding walls are self-supporting fences open on both sides and can be built on flat or sloping ground. Retaining walls are open only on the front side; the back side is buried as it holds soil back to create a raised level area in otherwise sloping land. Retaining walls, a requirement of terrain, are associated with hilly, rolling terrain, where it is necessary to hold back soil.

     Stone walls are incorporated into my designs for practical as well as aesthetic reasons. They increase the feeling of privacy by separating public sidewalks, for example, from your private garden. They also trap the sun’s heat, thereby creating microclimates, or provide casual seating along the tops of walls. Freestanding walls, in particular, provide a classic, durable background for a mixed perennial and shrub border, while at the same time separating (and therefore, clearly define the purpose of) areas of different character. For example, they separate the refined garden from the hay meadow or the outer edge of the lawn from the street. Retaining walls, sometimes with steps up through them, create terraces so that previously sloping areas become useful places for gardening or outdoor living.

     In the process of helping solve practical problems with slopes and lack of separation of spaces in a garden, stone walls also help provide a permanent garden structure and framework. They anchor shapes, forms, lines and levels, and in doing so, can relate the lines of the house to the lines of the garden. In summer and winter, they provide clean forms and a solid framework, and if skilfully built of indigenous stone, they add a feeling of age and permanence.

     Stone walls are either dry- or wet-laid. In a dry-laid wall, stones are laid on top of one another in a one-over-two, two-over-one pattern; the waller fills in the gaps with stone chinking or crushed stone as he builds up. The weight of the stones and the skill with which they are laid gives the wall its strength. In a wet-laid wall, the gaps between stones are filled with an inflexible binding mortar that provides the wall with some of its strength.

     One of the problems with wet-laid walls, which require the mason cover all but one side of a stone with mortar, is that the method is disrespectful to the stone itself. Once mortar has been applied and has dried, those stones are not reusable except as rubble in the interior of future walls unless someone wants to take on the laborious task of chipping off the mortar.

     Furthermore, the entire length of a mortared wall is one continuous solid mass sitting atop shifting earth. Stone in a dry-laid wall can shift with the movement of the earth underneath it, and if a stone or even a whole section tumbles off the wall during this inevitable movement in a 10- or 20-year period, it can be put back up. It’s not so easy to repair a mortared wall.

     There is one principle that holds true for both types of walls; they should appear to grow out of the ground, not balance on it. The base of a wall should be set at least four to six inches below grade so the base of any stone is not visible. If built of local stone, the wall will visually settle into the larger landscape. When building new walls on properties where old walls exist, build the new to match the old.

Building the Base of a Wall
If a wall is built on water absorptive material such as topsoil, the soil will freeze and thaw, thereby expanding and contracting throughout the winter. This can cause a wall to tumble over time. The key to a long-lasting wall is good drainage at its base.

     There are as many opinions for the construction of the base as there are stone wallers, but a good common sense attitude is this: The soil on which you are building the wall should determine the nature of the wall’s base. Take shovel in hand to see what kind of soil you’ll be building a wall on, and you will generally find one of three types of soil. If your shovel turns up gravelly well-draining soil or quickly draining sandy soil, dig a six- to eight-inch deep trench, lay down two inches of 1-½ inch (37.5 mm) crushed stone and start building atop that shallow base.

     If your shovel turns up topsoil that has a lot of organic matter in it, you are going to have to excavate down at least 12 to 18 inches or until you reach subsoil or gravel. Backfill that trench with eight to 12 inches or so of 1-½ inch (37.5 mm) crushed stone, and then begin laying the wall. When you put such crushed stone base in clay soil, water will be attracted to the voids between those crushed stones so, in a sense, you’re making a drainage ditch under your wall. Be certain that water has a place to run to. Extend the crushed stone base of the wall either at the ends or somewhere along its length so that you send water away from the wall and downhill. You can also put a perforated PVC drainage pipe within the base and run that downhill through the existing topsoil to daylight.

     If you need a crushed stone base for your wall, and you know how deep it has to be, you then need to determine its width. Here’s a good rule of thumb: for every one foot of height, extend the base one inch beyond both the front and back of the wall. For example, if a wall is two feet high, extend the base two inches beyond both the front and back of the wall.

     If you are going to build a new retaining wall, the banking must be cut back to a distance at least equal to half the height of the finished wall. Backfill the wall with the same 1-½ inch crushed stone you use for the base. Before backfilling the crushed stone at the back of a retaining wall, cover the crushed stone with filter fabric and then backfill with gravel or soil. The filter fabric prevents moisture-retaining soil particles from eventually filling the voids among the crushed stone.

Freestanding Walls
Freestanding walls solve many problems. If a home is too exposed to the road or street, a stone wall can form a separation between the two. To further increase privacy, plant shrubs and perennials along the inside of the wall. If that is too high-maintenance of an idea, consider building a four-foot high wooden fence atop of two-foot high freestanding wall to completely screen the view of traffic from house and garden and reduce noise. You can then plant low-maintenance trees or shrubs between the home and the wooden fence to settle it into the background. Stone walls can also permanently mark boundary lines.

     Freestanding walls also divide areas within your property to create outdoor living spaces, herb gardens or small, enclosed perennial gardens. Stone walls can enclose an entrance garden near the front door, or surround a small sitting area off the back of the house. By making gaps in freestanding walls you can create inviting entrances: onto walkways into the woods; as entrances to mown lawn paths down through a meadow to the pond; as formal or informal entrances into an outdoor dining area.

     Stone walls near buildings need to echo the proportions, dimensions and lines of nearby buildings so that building and wall relate. For walls at a distance from a house, pay attention to the architectural lines of the home as well. If you want to build a stone wall out near the street or road and the house is 50 to 75 feet from the road, build the wall so it is parallel with the front wall of the house, which may or may not be parallel with the street. In this way, the lawn area between the wall and the house is geometric; gardens can then be designed along both the wall and the house, and they will relate, contributing to a coherent garden.

     Good freestanding walls are carefully pro­portioned, typically two feet wide and two or three feet high, or three feet wide and four feet high, tapering back on both sides two inches per foot of height. The best freestanding walls are not necessarily the most tightly fitted and perfectly aligned; a wall built to perfection can be just as wrong as one sloppily built if it flies in the face of older, more relaxed walls already existing on the property. A satisfactory wall does not call attention to itself, and is built of local stone in a style and colour that matches older, existing walls, following the traditions of an area. Finally, a wall built with stones of a single colour or texture looks far more uniform and coherent than a wall built of a variety of stones.

Retaining Walls
The fundamental truth driving the construction of retaining walls is that people will readily walk or gather on level ground but will avoid sloping ground. By building a retaining wall anywhere from 18 inches up to three or four feet high, you can create level terraced areas. In doing so, you will not only tie the house visually to the landscape by extending the floor plane of the house into outdoor spaces, but also create more inviting spaces in which the family can walk, gather or garden. Since retaining walls remain cooler than freestanding ones because their back side is set into the earth, the exposed face of the wall can also become a place for vertical plantings.

     In many suburban communities, the area between the sidewalk and the front of the house slopes gently down to street level. Often there is little or no privacy and no chance for gardening at the front, so the gardening area exists only in the back yard. A retaining wall to create a level plane out front can be the first step in making a place for a semi-private or even totally private front or entrance garden.

     Measure the height of the front wall of the house and then build a retaining wall the same distance out from its foundation, thereby creating a level area, the dimensions of which are in direct proportion to those of the home. Plant low- to medium-sized shrubs in the soil behind the top of the wall to partially or fully screen the resulting level area from traffic, thereby capturing a front garden space. Build a stone walkway with steps from the sidewalk up to and through the stone retaining wall and on to the front door to create a welcoming entrance garden.

     Above four feet, most retaining walls lose human scale and people feel dwarfed standing next to them. When faced with the need to retain four feet or more of soil, design two walls, each around two to three feet high, setting back from the other, so as to create two shallower planted terraces rather than one tall one.

     Good retaining walls do not bulge out because of pressure from behind; skilfully laid, heavy cap stones allow anyone to walk on top of the wall, without shifting any stones. Furthermore, the placement of well-made retaining walls explains why the soil had to be level in that particular area of the garden. And like good freestanding walls, they don’t have big gaps between the stones. From a few feet away, the well-laid wall looks as though one person had built it. Finally, a good retaining wall has a batter, a uniform backward lean of perhaps two inches per foot of height, so that the wall is literally leaning back against the soil it retains.

Gordon Hayward, a purist on landscape construction with stone, built his career on gardening for clients while teaching high school. Today, from bases in Vermont and England’s Cotswolds, he is immersed in garden design full time through writing, lecturing and consulting.