A retaining wall is a constructed system typically built on properties with a sloped structure. The complexity of developing a retaining wall can range from a simple DIY to a challenging undertaking requiring a professional’s assistance. Either way, it’s vital to get the structure correct if you want to avoid a possible wall collapse.
There are a number of factors that lead to a retaining wall collapse, including materials used, improper drainage, soil stability, and faulty foundation — these highly impact a wall’s structural integrity. Working backwards, they are almost always the culprit.
It’s not only important to identify what factors could lead to a possible collapse of a retaining wall, but how to avoid or fix said issues. Ideally you’d want to prevent these problems from happening in the first place, as doing so would optimize your wall’s longevity.
However, if there’s an existing retaining wall already sagging or breaking down, you might want to look into ways to repair them without a full reconstruction (find out how much you can expect that to cost here).
Before we dive in, I want to emphasize that you should consult with a professional before undertaking any sort of project relating to your own retaining wall.
What Are the Causes of Retaining Wall Collapse?
There are several reasons why a retaining wall might experience a collapse. The majority, if not all of those reasons, have to do with the structure of the wall itself. It’s extremely crucial that research and time are put in on the front-end of building a retaining wall to prevent a breakdown in the future.
The main causes of a retaining wall collapse include material quality, foundation stability, structural integrity, and drainage systems. These factors need additional care and attention on your end, as they can be the decisive factors when it comes to your wall’s durability and longevity.
Let’s see how each of these components affects the quality of the retaining wall.
There are several materials you can use when building your retaining wall including, but not limited to timber, concrete, stone, brick, and so on. Even railroad ties are a reasonable material, as we wrote about here. However, it’s crucial to select the correct one for your needs.
Depending on the weight of the saturated soil being held back, certain materials may not be strong enough to withstand the mounting pressure. This is especially true when it comes to geographical areas that experience a lot of inclement weather like rain or freezing temperatures.
Wet soil heaves and expands, putting added pressure on your structure.
The foundation of the retaining wall is one of the most integral parts of the structure. The scale of the wall that you’ll need, what it’s holding back, and the pressure that will be applied on the structure will determine the foundation needed to prevent a collapse from happening down the line.
If the foundation is not built deep enough or not built properly, then heavy structural damages are likely inevitable. Again, the climate of your geographical area plays a big factor when it comes to how the foundation will need to lay in order to stand the test of time.
A good foundation is not the only source of support a retaining wall may need. Depending on the size of the wall or the weight of the soil the wall is holding back, the structure may need added support to continue to hold up.
There are a number of ways to give your retaining wall additional support if required. Thorough research and consulting with an expert are the best ways to determine which option would work best for you.
One of the best ways to prevent the pressure of wet soil from causing your retaining wall to collapse is to have a proper drainage system. If this step is overlooked or if the wrong materials are used to backfill the retaining wall, then water will collect and intensify the pressure applied on the structure.
This is especially true for walls that are built using one solid material like concrete. If interlocking blocks or stones are used, there may be a way in which water can disperse through the space in between the blocks.
How To Avoid Retaining Wall Collapse?
Retaining walls are built to hold in horizontal pressure from the landscape behind the wall. There are certain things that should be done to prevent a retaining wall from collapsing.
The best way to avoid a retaining wall collapse is to ensure the structure is sound while you’re building it. To do so, you’ll want to consult with a professional, gather the right materials, and use the proper techniques.
If an already-built retaining wall shows signs of damage, you may need to tear down the whole structure and rebuild it. However, it’s always a good idea to first consult a professional that can diagnose any problems you might have with your retaining.
Consult a Professional
Not all retaining walls are simple DIY projects you can do on a weekend. Depending on the purpose of the wall, the build may be more complex and above your knowledge or capability.
This is why it’s always a good idea to consult with a professional, even if you only do so during the planning phase of the project, in order to fully understand what you are undertaking. This is a sure-fire way to avoid some of the pitfalls that other do-it-yourselfers might fall into.
Get the Proper Materials
This doesn’t only refer to the substances your wall will be made out of, but also any other materials you’ll be using during the construction of your retaining structure, including the:
- Landscape fabric to hold the backfill material
- Backfill material itself (sand or gravel)
- Tampering tool
- Extra support (tie-backs, footings, steel reinforcements, etc.)
- Drainage (a pipe, tile, etc.)
Use the Proper Techniques
The majority of landscapers, when building a retaining wall on a property, will do so using a specific method called “step-back construction.”
What this means is that the wall will be built with a slight slant, leaning toward the soil it’s retaining. The reason the wall is built this way is to create pushback on the pressure of the soil the wall is retaining, creating a sturdier structure.
Additionally, when considering the foundation of a larger wall, make sure that the it is placed deep enough into the ground to avoid the effects of freezing weather. This means you’ll have to build the foundation below frost level. That way, when the ground freezes, then thaws, and is wet, the expansion of the saturated soil won’t affect the foundation.
Lastly, placing the backfill properly is also crucial for those wanting to ensure proper drainage. This means you’ll want to fill the wall with sand or gravel as you build, not all at once. Go tier by tier as a and be sure to use a tampering tool to make sure everything is as compact as possible.
A collapsing retaining wall can be fixed in certain cases (we wrote about that here), but it’s best to consult a professional to assess if you need to reinstall a drain, re-excavate, or just destroy the wall and start over. Foundation repair companies may be able to repair the foundation without needing to begin again by simply anchoring the wall or using a similar technique.
Now that you know the most common issues that can cause damage to your retaining wall down the line, you can avoid some of these problems by doing the proper work upfront. When in doubt, always consult a professional to ensure the safety of your family and home.
- Bob Vila: Lawn & Garden Repairing a Retaining Wall
- This Old House: How to Build a Retaining Wall
- Bob Vila: Retaining Walls 101
- Bob Vila: All You Need to Know About Retaining Walls
- DIY Home Improvement Forum: Adding support to existing retaining wall
- Charles and Hudson: Check the Frost Line by ZIP Code Before Digging Footings