When we design and build a stone retaining wall, our goal isn’t merely to change grade or hold back an embankment; we also aim to enhance the landscape. The retaining wall shown on these pages, for instance, which we built around a new in-ground swimming pool, provides seating and helps define a room-like space in the backyard. The wall was necessary because of the slope of the yard, but locating it between the pool and the house gave us the opportunity to create a landscape design as beautiful as it is practical.
Like the majority of the stone walls and fences we build, this one was installed “dry,” which means that no mortar was used. And while it isn’t exceptionally tall, stone retaining walls can be virtually any height (though a practical limit is about 8 feet); built right, they will last almost forever—or at least until the bulldozers come and redevelop the site.
On the other hand, if improperly built, even a low wall can quickly collapse into a pile of rock. What follows are the techniques we use to make retaining walls last as long as the stone they’re built from.
Native stone is best. While it’s possible to build a stone retaining wall out of practically any type of rock, we prefer to use native stone. There are two reasons for this: A native stone wall will look like it belongs in the landscape, and shipping costs will be significantly less.
Here in the Northeast, we can choose from a number of stones, including Pennsylvania bluestone, limestone, and fieldstone; all can be found within a five-hour truck drive and are available in various shapes, sizes, and colors.
To keep the cutting and fitting in check, we like to use stone with a flat bottom and a clean face. That way, all we need to do is dress the front of the stone with a hammer (to make it look hand-cut) and set it, which creates less waste and saves on labor and materials cost. Most sedimentary stones available in our part of the Northeast, including limestone and the sandstones (such as blue-stone), fit this bill.
Of course, each variety of stone works differently, and some need to be worked with a hammer more than others for a good fit. Some stone masons lay up walls without ever picking up a hammer; others—using special stone hammers and chisels—cut every stone.
I’m somewhere in between; I allow the site and the stone to tell me which approach works best. In certain cases, a wall will fit the site better visually if the stone is left in its natural state; other times, a more refined and worked stone looks better.
To build this particular wall, we used a Pennsylvania flagstone called Colonial Wall Stone. It’s actually a quarrying byproduct that would probably be discarded if not for its excellent qualities as a dry-wall-building stone. We buy it by the ton, paying about $150 to $200 per ton delivered; each pallet is filled with stones with (we hope) at least one flat face. The stones fit together quickly with little cutting, which allows us to work not only artistically but efficiently.
On a good day, an experienced waller and helper can hand-cut and fit about 2 tons, or roughly 25 to 30 face square feet (measured on the finished face of the wall).
