In the landscaping world, retaining walls have the major purpose of providing stability to the earth, preventing erosion and the movement of soil.
With San Francisco’s hilly grounds, retaining walls are an essential part of almost any household, apartment complex and business. Mud slides, ground seepage, crumbling dirt trying to take over your backyard – these structures are a barrier in the constant battle between man and nature.
Because of the ongoing war with gravity these structures are built to be burly and unstoppable. However, contrary to popular belief, these carefully engineered systems can also be aesthetically stunning. Not only do they hold back Mother Nature, but they also offer pragmatic benefits towards embellishing your home, such as providing privacy to your outdoor living areas and increasing the value of your home (which is a great return on investment, by the way).
Normally, retaining walls use their own mass, backfill anchoring systems to fend off the terrain behind it. They’re most commonly made with offset cinderblocks, angled stones, heavy blocks, wood or reinforced concrete frames, and then filled or backfilled. The fill source can be from just as many materials as the wall itself, but it has to have the necessary physical properties to act as a resistance to the natural earth pressures.
Types of Retaining Walls (and Examples of Landscape Projects You Might Use Them for)
When you think “retaining walls”, you may picture the oh-so-popular gray, imposing hunk of concrete. There are several types, however, and each one has a better use compared to another. For instance, a gravity wall (which you’ll read about shortly) is great for short terraces, but not so great for retaining walls over four feet.
Gravity Retaining Walls
Gravity walls are the oldest type of retaining wall, and are built to be bottom-heavy. Fatter at the bottom than they are at the top, they’re often built to lean against the ground they’re holding up. It takes math and a ratio to get them set right, but these walls are great for short terraces. At four feet tall or less, they won’t require mortaring or steel reinforcements.
An example of gravity retaining walls is this multi-terraced retaining wall and drainage project below.
Cantilever Retaining Walls
Cantilevers can hold a significant amount of dirt, and are good for tall slopes. They have a horizontal base that extends out to the back, and often to the front as well. For a cantilever wall to last and not come down eventually, it needs reinforcements (often steel) and some form of water drainage.
While a retaining wall with weep holes or a drainage system doesn’t very aesthetically pleasing, you’d be surprised to find out how beautiful it can be. Tamate Landscaping often uses stone facing and caps to turn a plain wall into a perfect backdrop for an Asian garden, or stucco covering to blend in with the Californian landscape like we did in Glenn Park. Click the link to read more about this retaining wall project.
Steel H Beam and Plank Retaining Walls
These walls are sturdy structures, and great for soft soil areas. They consist of beams driven into the ground at spaced intervals. Only about one third of the beams are above ground, with the rest below. They can be made out of steel, wood, concrete, or a mix, as we did in this Buena Vista retaining wall project in 2013. We buried the steel beams, then used treated wooden planks for the wall material.
When to Choose Terracing vs. a Single Tall Wall
When you’re working with a hillside in California, the decision between building a single tall retaining wall or breaking the slope into terraces comes down to slope, space, budget and design goals. A single tall wall works well if the slope is modest and you simply need one clean, level surface. But if the grade is steep, or you want planting areas, steps, outdoor-living zones or layers of garden, terracing can add both function and aesthetic value.
Terraces break the elevation change into manageable steps. They often make sense when:
- The height difference is large and one wall would be very high (and expensive)
- You want to build in garden beds, seating, different planting zones or flat terrace levels
- You want a softer visual transition instead of a huge wall
- The slope or soil/ drainage conditions make one big wall more complex
On the other hand, a single tall wall may be the right choice when: - The height to retain is moderate and access is easy
- You prefer fewer transitions and one simple flat zone next to your home
- The budget dictates a simpler build and the design doesn’t require layered terraces
In short: if your main goal is simply to hold back dirt and create one flat area for a patio or deck, a single wall may be all you need. If you’re looking for tiered garden space, outdoor living steps, multiple levels, or a more integrated landscape design, then terracing is worth considering.
Cost Ranges and Budgeting
Understanding realistic cost ranges before you start can help you plan your hillside retaining work with confidence. Across the U.S., the average cost to install a retaining wall runs roughly $35 to $65 per square foot, including materials and labor. In California (especially on hillsides), costs can vary widely. One example puts typical new wall costs in the range of $300 to $900 per linear foot depending on height, soil conditions and engineering needs.
Here are some of the main cost-drivers to keep in mind:
- Height and length of wall: The taller or longer the wall, the more material, footing, engineering and labor required.
- Slope and access: Steep or difficult terrain raises cost because of excavation, site prep and equipment logistics.
- Materials: Natural stone, decorative blocks or custom finishes cost more than simple block or poured concrete.
- Drainage and engineering: On hillsides, proper drainage and structural design are essential — skipping this can lead to failures (and future cost).
- Permits and structural requirements: Walls above certain heights often require engineer-sealed drawings, submit to local code and may require more complex foundation work.
Ready for your own retaining wall?
Now that you are a pro at retaining walls you can consider having one built. These walls have been around for years and continue to offer myriads of solutions and aesthetic landscaping additions. Take care of the evil slouch in the yard where you wanted to build a pool but never got around to it. Beautify the atmosphere of your home in the back yard, front yard or all the way around the house.
Contact Tamate Landscaping to discuss your landscaping project. Find out how a retaining wall can beautify your view.
