Retaining walls are found in the ancient archives of human history. They were used to alter the surrounding environments to control water and adjacent ground soil. They also defined boundaries and even served as barriers from invading outsiders. Today, retaining walls have withstood the test of time… And now the design—and purpose—of retaining walls is limited only by creativity and engineering design plans.
Of course, people often think bigger is better. There are examples of retaining walls extending hundreds of feet in the air. One that comes to mind is the Great Wall of China, which is simply a double-sided retaining wall with reinforced clay and gravel base. Building a higher wall or a higher building is every designer’s dream: A wall that can literally reach the clouds.
Most homeowners and businesses probably have no reasonable use for a retaining wall extending several hundred feet into the air. But for a variety of reasons, businesses and individuals alike may want a retaining wall to be at least one foot higher than the neighbor’s wall… If for nothing else than bragging rights. You might want a high wall to prevent strangers from peeking into your backyard. Or maybe you want just a little more peace and quiet to enjoy the efforts of your labor in creating the landscape of your dreams.
Here’s the million-dollar tip: You can probably build a wall as high as you desire… within certain limits, listed below.
Research And Consult Before You Build
Before you rush out and start gathering materials for the wall-of-all-walls, there are a few things you may need to consider.
Local Restrictions May Apply To Retaining Walls
Most cities and local municipalities usually have height and design limitations for retaining walls over a certain height… These may vary by location and for good reason. Higher walls exert additional pressure on the ground soil, which may impact the soil erosion process, movement/sliding and drainage away from the wall. All of these are serious considerations with higher retaining walls. The math is not complimentary in most instances… which means that building a wall twice as high does not equate to building a wall twice as strong. You need an even stronger wall than that.
North Carolina Building Code Section 1807.2.5 Rev: 2 requires that a North Carolina Registered Design Professional design any retaining wall that is “more than five feet in height of earth within a linear 50-foot distance measured perpendicular to the retaining wall.” The building code also notes that vertical height (relief) is the difference in elevation from grade level on the open side of the wall to the grade level on the fill side of the wall.
Therefore, before erecting that 10-foot wall—which will divert thousands of gallons of water to your neighbor’s property—it’s best to consult your local municipality and hire a professional.
Note: Heritage Block walls over four feet may have to be engineered.
Fun fact: To date, Heritage Block’s tallest retaining wall measures some 47 feet and is located at the Volvo test track in Virginia. We were able to create a natural looking wall without sacrificing performance.
Additional Considerations For Construction Of Retaining Walls
Design construction: This is the most important consideration for retaining walls extending above four feet. There are several types of designs available; however, it is best to consult with a professional and experienced engineer to come up with a design that best fits your specific landscape. In general, most professionals will be familiar with the following types of retaining wall designs:
- A gravity wall uses the wall’s own weight to withstand the pressure of the earth and/or water.
- A cantilever wall has a concrete footing, which retains soil. The rear of the footing is counterbalanced by the same soil trying to topple the wall.
- A counterfort wall is similar to a cantilever wall, except that it has a tee section that is perpendicular to the main wall. Thus, the tee section essentially acts as a beam.
- A buttress wall has the tee section on the front of the wall, making the larger part support system in the front of the wall.
Each landscape will require its own unique construction, which, again, is best left to the professionals for walls over four feet.
Proper base construction: Depending on your design, soil type and drainage system, the base of the retaining wall is a critical feature. It’s important to take into account the relevant factors such as soil displacement, soil composition, annual rainfall and adjacent structures. Failure to do so can mean the difference between a retaining wall withstanding the test of time, and one that slides down the hill side during the first extensive flash flooding rain: A catastrophic failure.
Other Considerations: You should also take into account such things as environmental concerns, flood evaluations and the purpose of the retaining wall.
When installed properly, retaining walls can provide years of enjoyment for you and your family and friends. For your convenience, please feel free to check the Heritage Block retaining wall installation guidelines.
Our blocks can transform any outdoor space into a unique masterpiece… The options are truly LIMITLESS. For everything you need to plan, design and build the perfect garden or retaining wall for your next project, contact us today: (919) 562-5005