About Brick, Block and Stone Retaining Walls

Retaining walls are an excellent and durable solution to controlling erosion. They are commonly used for creating different grade heights on a sloped piece of land. Terraced retaining walls can provide a beautiful landscape display as well. Retaining walls are also used to build elevated patios, planter boxes, and much more.

We can build retaining walls using a variety of methods and products. The most common product used for building retaining walls are retaining wall blocks. These blocks can be interlocked with a built-in notch and channel, glued together with a strong masonry adhesive, or some block systems use fiberglass pins to interlock each course. Retaining wall blocks can range in size from small garden wall blocks, which can be used to border landscape beds to very large sized blocks that are strong enough to retain large amounts of land up to 10-20 feet in height. Some other options to consider for building landscape retaining walls are boulder walls, ledge rock walls, stacked flagstone walls, and timber walls, which can often be a more cost efficient option. For boulder walls, we usually use what are called "Michigan boulders" for our projects. These boulders are the most common at landscape supply stores in the area. They typically can range anywhere from a few inches up to 4 feet in size. Ledge rock walls may consist of many different types of large aggregate from throughout the country. A traditional ledge rock sold in our area is known as "Michigan limestone ledge rock". They are usually 6-8 inches in thickness, 2-4 feet in length, and 1-2 feet in depth. Stacked flagstone walls are great for bordering landscape beds. These walls should not be built any higher than one foot. They provide more of an aesthetic appeal and do not have much strength for retaining solid earth. There are dozens of different types of flagstone to choose from to create a natural style landscape wall. To name a few, there is Ohio Blue, Canadian Buff, Chilton, and Grand Canyon. For timber walls, we use pressure treated timbers, usually 6"x6"x8'. Half inch rebar is used to reinforce the timbers.

When building a block retaining wall to retain an area of land, the first step is to excavate the subsoil and install base materials. The depth of the base material will vary depending on the size of the block and the height of the wall. We prefer to use 21AA limestone for the gravel base and slag sand for the final leveling agent. Once the base is prepped, it's time to start stacking block. Each course of a block should be back set to provide extra strength against the land it is retaining. Depending on the height of the wall, layers of geogrid can be installed to strengthen it. Once the wall is built, we install clean limestone behind the wall (about one foot in depth for every two feet in height) to allow any water build up to drain behind the wall. First, a thick woven fabric is placed between the subsoil behind the wall and the clean limestone to keep any soil particles from washing into the clean limestone. If there is a large surface area of land pitching toward the retaining wall, we recommend installing a sock drain or French drain system to help carry the water away from behind the wall. When installing boulder walls, we slightly excavate the soil and place the first course of boulders directly on the ground. Each course of boulders is set back to apply pressure on the land they are retaining. We install heavy woven fabric directly behind the boulders to control any erosion. If needed, a layer of clean limestone may be applied to the wall as well. To build a ledge rock or timber retaining wall, we excavate the subsoil to the proper depth, and then install clean limestone for the base. Once the walls are built, we do the same procedure described above, adding clean limestone and fabric behind the walls.