About Dry Stack Stone Retaining Walls
- Dry stack stone retaining walls have been used in landscaping and farming for centuries. Remains of stone terraces from the mid-19th and mid-20th centuries can still be seen on the land in many areas of the northeastern and south-central United States as well as many other countries such as Ireland. In Europe dry stack stone walls are everywhere and are still being used for farmland. These are excellent for gardening on a hillside.
- A dry stack stone retaining wall is a structure that built without mortar and is usually built against a slight hill and prevents the down-slope movement and erosion of earth from sliding into a building, road or other area. Because this type of wall is built without mortar it can naturally drain moisture from the soil as well as shift to accommodate the ground when it freezes. There is no need to build a foundation below the frost line. This type of wall also appeals to many people for its historic look.
- Dry stack stone retaining walls can be any length but are generally not built over 3 feet high. Any higher and they become less stable without concrete footing. Many taller retaining walls are reinforced with steel or concrete rods or wire baskets filled with rocks. According to the International Building Code, "retaining walls are required to be designed to ensure stability against overturning, sliding, excessive foundation pressure and water uplift; and that they be designed for a safety factor of 1.5 against lateral sliding and overturning."
- There are different looking dry stack stone walls and each one depends on the type of stone it is built with. Some people may prefer to purchase cut field stone, granite or other rock which is sold by the ton on wood pallets. This is a fine option if one wishes to make their retaining wall appear uniform and even or if one does not own land with a lot of rocks on it. For those that do have tons of stones at their own dispense the shape of the rocks is still important. Successful stones will be somewhat flat and angular for stacking.
- The dry stack stone retaining wall is much cheaper than other mortared walls however it must be built properly. Earth pressures can push the wall forward or overturn it and any groundwater more than regular moisture behind the wall that is not dissipated by a drainage system causes additional horizontal pressure from behind the wall. Dry stack stone retaining walls are considered to be a gravity wall meaning they depend on the weight and mass of the stones they are built with. To resist these pressures pushing from behind the wall they are built slightly set back against the wall they are retaining. A trench of about 6 inches is usually built for the first layer of stones and each layer is set back 2 inches or so every foot in height.