How To Build A Retaining Wall In Sandy Soil

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Retaining walls maximize space in your landscape while offering an extra accent and added protection for the soil. There are many types of soil, though, including sand, clay, silt, and more. Are you working with sandy soil and wondering if building a retaining wall is doable? Good news, it is. Furthermore, sandy soil happens to be ideal as it allows for good drainage. In this article, we will use our combined research to give you a step-by-step guide on building a retaining wall in sandy soil and more. 

To build a retaining wall in sandy soil, follow these steps:

  1. Plan your layout
  2. Dig your trench
  3. Lay base material 
  4. Install blocks
  5. Backfill your wall
  6. Cap your wall

These are the basic steps to building your retaining wall. We will go on to explain each step in detail, including product recommendations. Read on for these detailed steps and insights into when you need to bring in a structural engineer. 

ornate gated entrance of country villa house with retaining wall. How To Build A Retaining Wall In Sandy Soil

How To Build A Retaining Wall In Sandy Soil

Sandy soil is a granular mix with little to no fine particles, meaning it is less likely to stick together and block drainage. Since water cannot pass through your wall, this well-draining soil creates ideal conditions. But, you need to gather all your supplies and material before you start your build. Supplies and tools you will need for this project include:

benches under the retaining wall in an Italian baroque garden. the wall slopes to the side and is finished with a stone carved volute in the shape of a spiral.

  • Shovel
  • Tamper
  • Tape measure
  • Level
  • String line
  • Safety glasses
  • Hammer/Mallet
  • Spade
  • Base material
  • Bricks
  • Backfill

Materials for backfill, your base, and even the bricks you use can vary. The choice comes down to preference and drainage needs for your landscape. Let’s start breaking down the steps of building your retaining wall in detail. 

1. Plan Your Layout

When planning your wall, you need to consider how tall and how long your retaining wall needs to be. This will help you determine how many blocks you will need, as well as other materials. Use your string and stakes to mark the position of the wall and where you will dig your trench. 

You find a mason line here on Amazon to help you plan your layout.

Before you move on to step 2, you should check with your local utility company to see if there are underground utilities or cables where you plan to place your wall.  

2. Dig Your Trench

With your layout set, you can dig a trench using your laid line as a guide. The base is the most important part of the retaining wall, as it will define the stability of the whole thing. Your trench needs to be deep enough to house your base material and cover 1 inch of every 8 inches of height of your first row of blocks. 

Take a look at this steel tamper here on Amazon.

Use your tamper to compact the soil at the bottom of your trench. To get the base as level as possible, use your level to even out the ground layer of soil as you tamp. 

3. Lay Base Material 

After your trench has been dug and level, you will lay the base material. Your base layer should be 5-6 inches thick after being compacted. This layer can be made from crushed stones or concrete. You want to use a material that will not sink into the ground layer once the weight of your blocks is on top. 

4. Install Blocks

Begin installing your retaining wall blocks with your first layer directly on top of the base material. As you lay each block in the first row, you want to ensure all sides are level before moving on to the next block.

The base material and your first row of blocks are crucial components to the strength of your wall. Take your time installing each block as it will save you time and work in the future. 

Amazon offers a 3-piece Spirit level set here

Read more on our blog post, “Should You Glue Retaining Wall Blocks?”.

5. Backfill Your Wall

As you finish a row of your blocks, you will backfill the space behind the row. You can use the same material as you used in your base here, crushed stone or concrete. This layer of backfill will add to the drainage when the retaining wall is complete. Brush off any debris from your blocks before starting the next row. 

6. Cap Your Wall

Not everyone caps their wall, but it does aid in the protection from weather erosion and adds stability. This step makes for a sturdy wall with increased longevity. You can use concrete to keep the cap in place or use a liquid adhesive. 

You can find a heavy-duty adhesive here on Amazon.

The video below provides a detailed visual for these steps to building a retaining wall, including a few extra tips and tricks: 

Learn more on our blog post, “How To Build A Retaining Wall On A Slope.”

Can You Build A Retaining Wall On Sand?

You can build a retaining wall on sand. If you are a homeowner living on or around sand dunes, you can benefit from a retaining wall along your property line. The weight of sand is even helpful with retaining wall projects because it can help stabilize the wall. 

The video below is an excellent example of a retaining wall built on sand. 

Read more on our blog post, “Can You Build A Retaining Wall On Concrete? [Plus How-To Tips].”

What Soil Is Best For Retaining Wall?

The ground you plan to build a retaining wall on must be solid, strong, and not moist. The soil is the foundation of the whole project, making the integrity and strength critical. 

Retaining wall and wooden barrier on empty beach against blue skyline and residential buildings on beach

Sandy soil is the best soil for retaining walls. Sandy soil offers optimal drainage and provides the strong base you need. On the other hand, clay soils can be the worst to work with due to their wet nature. 

Learn more on our blog post, “Does A Retaining Wall Stop Water [And How To Add Drainage].”

What Is The Cheapest Type Of Retaining Wall?

If you are working with a budget, you might be wondering if there are cheaper options for building a retaining wall. After all, the price of individual blocks does add up. The most inexpensive type of retaining wall is one made from poured concrete.

retaining seat wall made of pure cast concrete blooms purple flowers behind it the wall is bordered by metal fences

The price of poured concrete per square foot is slightly less than interlocking blocks and about half the cost of building a stone wall. One downside of poured concrete is it offers little to no drainage. You will need to ensure water can be drained in other ways and add an extra step to your project.  

Do I Need A Structural Engineer For A Retaining Wall?

Walls that are under 4 feet high often do not require a structural engineer for building. There are, however, many instances where you do need to consult a structural engineer. Reasons you would need an engineer for building a retaining wall include:

  • Walls over 4 feet high
  • Your wall will be terraced
  • Cars, motor homes, or other large vehicles will be on top
  • Your wall will be sloped on the top

two tiered curved concrete retaining wall made of sectional preformed concrete blocks

As you are planning your retaining wall, consider the above. If your wall includes multiple of these characteristics, you have a complicated design, or you are building around sensitive structures, you need professional help.

Outside a structural engineer, another professional you should be consulting is your community’s building community. There may be additional regulations you need to follow based on where you live. 

Read more on our blog post, “How Tall Can A Retaining Wall Be [Inc. Without A Permit]”

Concluding Thoughts

You can build a retaining wall in sandy soil, and for the reasons mentioned, these conditions are ideal. Sandy soil offers excellent drainage, which will benefit your wall in the long term. Building a retaining wall in sandy soil can be done using the steps detailed here.

These walls can even be built in just sand. Consider adding additional structural support in these cases, like mentioned in the video. We hope you found this article helpful when working on a retaining wall in sandy soil. Enjoy the project. 

Are you looking to take your retaining wall to the next level? Have a look at our blog post, “Should You Add A Fence To Your Retaining Wall? [And How To Do So]”

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