Retaining walls can really transform an outdoor space — both physically and aesthetically. However, they’re unique among outdoor fixtures because they have such an important job. They’re used for a variety of purposes but generally keep soil from falling where it shouldn’t be.
This is important because those locations could include walkout basements, tiered garden landscapes, sunken patios, and so on. Failure means costly repairs!
If you’re building one, there are a lot of factors to consider. And among those are how far your retaining wall should sit from your home’s foundation.
A retaining wall should sit as far back from the house foundation as possible. This usually falls in the range of 3’ to 15’ (7.62 to 38.1 cm) of distance, but special circumstances could require more or less. Retaining walls should also lean toward the soil they’re retaining to offset pressure.
When installing a retaining wall, there are quite a few factors to consider to ensure that the wall will last and properly keep erosion and water drainage away from your home’s foundation. Otherwise, you could be dealing with a wall that bulges or, worse, crumbles.
As always, if in doubt, contact a professional. Online research is no substitute for trained expertise.
How Should a Retaining Wall Be Built
Small retaining walls can be tackled by the home project savvy individual, but it is always best to consult a structural engineer or architect when taking on a large endeavor. Depending on the scale of your retaining wall, you may also need to get a permit from your local authorities before building it.
Whether taking up the task yourself or consulting a professional, it would be beneficial to be educated on a few factors when it comes to building a retaining wall.
- Foundation
- Support
- Materials
- Backfill
- Drainage
Taking a deep look into each one of these elements will give you a better understanding of what to look for during the process of building a retaining wall and how to ensure your project is as long-lasting as it could be.
Foundation
The type of foundation you’ll need will likely depend on the size of the retaining wall you’re looking to build. For example, a gravel-filled trench might be suitable for a small retaining wall but would not suffice for a larger project.
This is due to the nature of the soil, which can shift about, especially if the weather in your area tends to be unstable.
If your retaining wall is a bigger project, you may need to consult with an expert. This build may require a buried structural footing which would entail a landscaper pouring a concrete base below the level at which the ground freezes.
This is done to prevent any movement of the wall itself when temperatures drop and moisture in the soil heaves and shifts. We actually wrote a comprehensive guide on building a proper retaining wall base, which you can read here.
Support
Due to the purpose of a retaining wall, it is crucial that it has the proper support to last. When constructing a retaining wall, most builders will use a design called ‘step-back construction,’ in which the wall is built at a slant toward the soil it needs to contain.
This should provide enough support to ensure the wall is structurally sound, but if not, there are a plethora of other support options, including but not limited to cantilevered design, buried footings, tiebacks, or steel reinforcement.
Tiebacks are connected to a range of anchors deep in the ground called “dead man.”
Materials
The most common types of retaining walls are concrete, interlocking blocks, timber, railroad ties, and stone. Each requires its own specific materials, but the basics of a retaining wall remain the same.
The materials you will need for your retaining wall include landscape fabric and backfill.
You’ll have to consider the scale of the wall, the soil drainage, the weight of the soil being retained, and prep when purchasing your concrete, block, or timber.
Each type of material has its pros and cons. For example, while concrete might be the most stable and long-lasting, it is also the most expensive, and it’s not exactly aesthetically pleasing. Regardless, the structure should always be the first priority; otherwise, you’ll have to deal with sagging and possibly an eventual breakdown.
Backfill
Backfill will help ensure that the retaining wall you build doesn’t crack or break due to pressure. Dirt and soil expand when wet, which means they will get heavier, placing added pressure on your wall. In order to prevent this, you have to fill the back of the wall with materials that won’t swell when coming in contact with moisture. The most commonly used materials are gravel or sand.
When adding backfill consider landscape fabric, which will help prevent the matter that settles to the bottom called sediment from clogging up the backfill and drainpipe. Additionally, backfill should be added little by little as the wall is being built, not all at once, to ensure it settles correctly and is compact.
A technique you can use as you add the backfill to make sure it is as compact as possible is called tamping.
Drainage
The type of wall you build will determine how you should handle drainage. For example, walls that aren’t completely solid, like stackable interlocking blocks— with proper backfill— may not need added drainage, as water can disperse through the spaces in between the blocks.
However, solid concrete walls may require a drainage pipe or drainage tiles to redirect the water away from the wall to prevent it from collecting, which could cause damage to your wall and possibly your home’s foundation. Without controlling the flow of the water, you’re more subject to erosion.
Conclusion
Whether you’re planning a DIY project or calling in experts to build your retaining wall, you now have an understanding of the undertaking you are about to embark on.
You can gauge, depending on your needs and landscape, what kind of wall you need, what materials would work best, and the necessary steps to complete your project.
Most importantly, you now have the knowledge on what to look out for in your build that could cause potential problems down the line and how to avoid them. All that’s left is to plan and build the most durable retaining wall.