How To Build Dry Stacked Natural Stone Retaining Walls

Dry Stacked Natural Stone Retaining Walls

Purchasing Your Boulders/Wall Stone: 

When looking for natural stone for your future retaining wall, first search for “gravel pits” in your area. Because they are in the excavation business, they have access to the many boulders buried in their pits, often setting them aside for sale to landscapers (or other consumers in the know). Keep in mind, however, the machines they use are extremely large and therefore unfit for loading boulders into your truck or trailer. Because of this, you will find it necessary to either load them by hand (which can be very difficult because of their shear weight and awkwardness) or you will need to rent a small loader.  If you rent a loader to load the boulders, you will have to unload them by hand at the jobsite. This too can be difficult if you do not have a dump truck or trailer. However, with patience and the proper tools, you can do it this way and save yourself a lot of money. 

Stone Yards are another option. These are very popular for several reasons: First, they can save you a lot of time and labor. Stone yards can load the boulders for you if you have an open-bed vehicle. Also, stone yards generally offer delivery. Second, stone yards have access to a wide selection of stone from all over the country. The best yards can obtain stone from all over the world. However, with selection comes increased price. Stone yards sell stone significantly higher than gravel pits. They probably purchase their boulders from gravel pits and must recover the cost of shipping the stone from the pit to their own site. Not a cheap thing to do.

Depending on your location, you may be able to save even more money by scamming fieldstone from fields in the area. Especially keep in mind any farms or ranches you may have seen while driving around lately. Farmers often have large piles of boulders moved aside while preparing their fields for planting. Before you make off with any boulders, make sure you get permission from the owner of the property from which you intend to "pilfer".

Choosing the Right Stone For Your Dry Stacked Stone Wall Project:

Types of Natural Stone Available for Retaining Walls
Weight and Dimension:

It is essential, when choosing your rocks, to keep a few things in mind. You may think my first recommendation is obvious, but it must be said. It is easy to find boulders you love at the stone yard only to discover when you get them to your site you can’t budge them. So, plan ahead. Know how you intend to manipulate your boulders once they’re home. Don’t choose boulders that you cannot move. That does not mean you must be able to pick them up. However, you must determine your ability to access and use the tools necessary for the project. (I will take you through some of the many options available, and how to utilize those later).

Because stone density varies due to composition, it is impossible to give you precise weights per boulder or square face foot. Nevertheless, I have taken the time to give you some estimates based on my experience and those of other professionals. Below are estimates of weight based on dimension for various regions and rock type:

*Face feet assumes average thickness of the wall is 18".  Actual thickness will affect Face Feet.
*The List Below is stone readily available in Michigan:

Region                          Rock Type                    Estimated Weight                       Pounds/Face Foot

Pennsylvania/NY         Bluestone                      162.5 pounds/cubic foot             243.75 lb/face foot
Wisconson                   Chilton                          168 pounds/cubic foot                252.00 lb/face foot
Wisconson                   Fon Du Loc                   162 pounds/cubic foot                243.00 lb/face foot
Mid West                     Granite                          160 pounds/ cubic foot               240.00 lb/face foot
Michigan                     Michigan Fieldstone     170 pounds/per cubic foot          255.00 lb/ face foot
Michigan                     Michigan Limestone     155 pounds per cubic foot          132.50 lb/ face foot
Canada                        Canadian Limestone      165 pounds per cubic foot          247.50 lb/face foot
Michigan                     Grindstone                     136 pounds per cubic foot          204.00 lb/face foot

The Right-Size Wall Stone for Your Project

Building Stone: Different natural stone wall projects call for different size stone. For the sake of stability, use the largest boulders you can handle.  Retaining walls under two feet tall can be built using 10-18” boulders. Vary the sizes and shapes in order to give it a more natural look. Larger walls should be built using 18”-36” boulders. Boulders over 24” will probably require a machine to install.

Small Boulder Retaining Walls and  Rosetta Dimensional Steps

Shims: Whatever the size of the boulders you intend to use always keep some smaller angular stones handy for use as shims. Shims are used to increase contact between rock surfaces and thus improve stability. They can also help stablize rocks that rock.  Use a sledge hammer to set any shims that will be filling spaces between boulders.

If the soil at your sight is rich in either clay or humus, you will need crushed stone and rubble for backfill. Proper backfill improves drainage and keeps frost heave (a problem in cold northern parts of the county) from shoving boulders out of your wall. 

Building Your Retaining Wall

Before you do anything else, locate any underground utilities. Most municipalities have programs set up to provide free or inexpensive utility location. Give them a call. In Michigan you need to call MISS DIG. Next, mark out the base of your retaining wall using spray paint. Make sure you keep in mind the set back. Allow for a minimum of 1 inch set back per 12 inches of height. For walls over five feet, set back should be 1.5” per ten inches of height.  Once you have marked out the front of your wall, begin digging a trench approximately 1 ½ times the depth and 2x the thickness of your average wall stone.  Dig 6-12” in front of face of the wall.  Boulder Walls can be built by simply digging individual stones into the soil so they sit about 1/3 of the total height into the ground.

Chilton Dry-Stacked Retaining Wall

If you are using stacked  stone such as Chilton or Bluestone, it will be necessary to dig at least six inches deeper than the average thickness of your stones.  This will allow for a compacted "chips n dust" or crushed concrete base.  You will need to dig your trench  wide enough to allow for a minimum of 6 inches in front, and 6 inches behind the wall's base layer.   Thus, if your average wall stones are one (1) foot wide, front to back, you will dig your trench 2' wide.  Doing this will ensure a stable base and keep your stones from sinking or tipping forward or backward.  

To learn more about my services and begin planning your professionally designed and installed retaining wall project,

Call or Text Brent NOW

(616) 328-3258.