It’s natural to be concerned about the structural soundness of an aging retaining wall or a retaining wall that you are having constructed in the Canton and Troy, MI, areas. Putting off repairs or replacement, or hiring the wrong hardscape contractor, would be a regrettable mistake and potentially catastrophic if your retaining wall is vital to your landscape. Some homeowners don’t realize just how powerful the forces of soil are against a retaining wall—underestimating these forces can lead to the wall’s failure, which could mean significant damage to your home or property and an expansive wall-rebuilding project. Here’s what to look for, and how to avoid problems.
Related: Guide to Segmental Retaining Walls
Although a retaining wall can be purely decorative, the main function of retaining walls is to prevent movement of soil on sloped lots. Walls form a barrier designed to prevent soil from shifting or sliding downslope, especially in areas without trees or dense vegetation or in areas that are prone to heavy rain or flooding.
Signs of Impending Wall Failure
If you notice any of the following conditions, you will want to look into repairing or replacing the wall immediately.
If your retaining wall is tilted forward; if it is cracking, bulging, or crumbling; or if it has flaking veneer, this could mean that the forces of the earth are more than the wall can handle, and it is about to fail. A more subtle concern can arise if you notice weep holes that are clogged with debris. Clogs prevent water from draining, and collect it behind the wall.
A Well-Built Retaining Wall
Earth, rock, and debris exert tremendous pressure on a retaining wall. However, a retaining wall doesn’t necessarily have to support the many tons of soil behind it; it just has to hold back the disturbed soil (the fill), which will then support the weight of the original, undisturbed soil. As gravity pushes the weight of the fill to the lower part of the retaining wall, that wall—including its footings—has to be structurally capable of withstanding that pressure.
In addition to soil, retaining walls have to control water. Water buildup behind the wall saturates the soil, creating immense added pressure especially in areas with a strong freeze-thaw cycle.
A well-built wall allows water to drain from the fill area to relieve this pressure. But don’t be fooled. The presence of weep (drainage) holes in a masonry retaining wall are sufficient to allow enough water to drain out to relieve the pressure building behind the wall. A good drainage system behind the wall is necessary, and weep holes must be kept free of debris.
Even well-built walls can fail if they are too tall. Any retaining wall taller than 4 feet requires the expertise of an engineer. The materials alone (stone and mortar) are not strong enough to hold back the relentless pressure of water-soaked soil. A solution could be a heavy-duty engineered wall system with additional supports built into the slope itself; or a series of tiered retaining walls. Here, too, engineering will be required to prevent the upper tiers from adding pressure on the lower tiers.
Thorough foundation work, a proper slope, adequate drainage, and the use of the right materials will ensure a wall that lasts—and does its job. But if you’re noticing even one of the warning signs, take action now to ensure the structural stability of a retaining wall!
