How to Select Different Types of Retaining Walls for Every Site
Why the right retaining wall type matters
Honestly, most people see a retaining wall and just think, well, it’s a wall. But when you’re in this line of work, you see the physics. You see the immense pressure that a whole hillside is trying to exert, day in and day out. Choosing the right wall isn't a cosmetic decision; it's about holding back a literal force of nature. Get it wrong, and you’re not just looking at a crack. You’re looking at landslides, foundation damage, and a fix that costs way, way more than doing it right the first time.
I remember when a homeowner called us in a panic after a big storm. The cheap wall their last contractor built was visibly bowing, and their patio was starting to sink. It hit me that they never even had a soil test done. They just picked a wall that "looked nice." We had to tear it all out. That's why we start every single project by getting our hands dirty, looking at the soil, the water, the slope—all the boring stuff that actually keeps you safe. It feels like an extra step, but skipping it is the most expensive mistake you can make.
Need a deeper dive into site analysis? Check out our rundown of structural engineering services and the importance of thorough soil investigation and geotech testing. Otherwise, read on to learn more about the different types of retaining walls.
Gravity (mass) Walls: Solid, Simple, and Durable
Here’s the thing about gravity walls—they’re the old-school, straightforward answer. Their strategy is just pure, simple mass. Think of it like a heavyweight fighter leaning into a punch. There’s no fancy footwork, just enough solid weight to refuse to budge. We build them from concrete, stone, or these big interlocking blocks. Because the wall is so massive, it’s mostly fighting against being pushed over, which means you don't need a ton of complex steel reinforcement inside. It’s an honest, what-you-see-is-what-you-get solution.
Footprint and setback: A broad base (of around half the height of the wall) shifts the centre of gravity toward the slope, boosting stability.
Drainage: Perforated pipes, weep holes, and free-draining backfill can be used to relieve hydrostatic pressure.
Load limits: Heavy surcharges (e.g. from traffic or storage yards) might push designers toward cantilever or anchored systems instead.
And they don't have to look like a fortress. The modular blocks these days come in different textures and colors, so you can make them blend into the landscape. For a lot of residential projects where you have the space, this is still our first recommendation. It's reliable, it doesn't break the bank, and it will probably outlast the house behind it.
Cantilever and Counterfort Walls: High-Performance Engineering
Okay, so what happens when you don't have the space for a massive gravity wall? That’s when we have to get a little more clever with the engineering. A cantilever wall is the smarter, more efficient design. It works using leverage. The wall itself is a thin stem, but it’s connected to a wide footing underground shaped like an "L." The weight of the earth sitting on the "heel" of that footing is what actually holds the wall in place. It’s basically using the soil’s own weight against itself. Pretty cool, right?
And if you need to go really high, we add what are called counterforts. They’re like these triangular ribs that connect the wall to the footing, giving it extra bracing so we don’t have to make the whole thing thicker. It's a way to get more strength without pouring tons more concrete.
Subgrade prep: A uniformly compacted granular base to avoid differential settlement.
Drainage: Filter fabric, perforated drain pipes and weep holes every 1.5 meters to keep hydrostatic pressure in check.
Seismic and surcharge checks: Finite-element modelling ensures that the wall meets KS 02/T/2024 seismic provisions and live-load demands.
Interested in learning more? Click here to explore similar tall-wall solutions amongst our commercial structural design projects.
Anchored and Sheet-Pile Walls: Slim Solutions for Urban and Waterfront Sites
When you’re building in a city, or right up against a property line, or down by the water, you have zero room to play with. This is where anchored and sheet-pile walls come in. They are the super-slim, high-strength solutions for impossible spaces.
Anchored Soldier-Beam/Tie-back Systems
Think of these as walls that are literally screwed into the earth behind them. We drive these steel beams into the ground and then drill anchors way back into the stable soil, locking the wall in place. It's like the wall is reaching back with a bunch of strong arms to hold itself up. This lets us build incredibly tall, thin walls that are perfect for deep excavations or building basements right next to other structures.
Sheet-Pile Walls
Sheet piles are a different beast. It's like taking giant sheets of steel and driving them into the ground one after another, interlocking them to form a solid, continuous barrier. Because they lock together so tightly, they’re fantastic for holding back water, which is why you see them all the time along rivers, canals, and for building cofferdams. Plus, you can often pull them out and reuse them, which is a nice little bonus for the environment.
Corrosion protection: Epoxy-coated or cathodic systems in saline zones can help to prevent erosion.
Groundwater control: Well-point dewatering behind the sheets can prevent issues with groundwater.
Permits and neighbors: You and/or your engineer will need to consider environmental approvals and party-wall agreements.
Mechanically Stabilized Earth (MSE) and Modular Block Walls
At first I didn’t get MSE walls, I’ll admit. The idea of using fabric and soil to build a massive wall just felt… wrong. But then I saw one go up for a huge highway project, and it clicked. You’re not just building a wall in front of the dirt; you’re actually reinforcing the dirt itself, turning the entire soil mass into one giant, stable structure. We do it by layering synthetic grids or strips within the backfill as we build up.
It’s an incredibly smart system that lets us go super tall without the massive concrete footprint of a gravity wall. It’s also surprisingly flexible.
There are a number of advantages to MSE systems, including:
Speed: Pre-cast panels or dry-stack blocks can be installed quickly, trimming programme time by ~30% versus cast-in-place systems.
Curves and tiers: Radius walls and terraced landscaping are simple with modular units.
Resilience: Minor settlements dissipate through the reinforced fill without cracking.
Here are the design essentials you’ll want to consider:
Backfill quality: Non-plastic, angular aggregate maximizes pull-out resistance.
Drainage: Blanket drains and heel outlets keep water pressure at bay.
Facing connections: Stainless or hot-dip-galvanized hardware can withstand tropical humidity.
Keen to know more? Explore the basics in our slope and embankment reinforcement guide, then find out how our retaining wall inspection service can provide ongoing maintenance and support.
Specialty and Hybrid Retaining Walls
Every now and then, a project lands on your desk that just doesn't fit the standard playbook. The geology is a mess, the client wants a very specific look, or the space is so tight it seems impossible. That’s when we get to pull out some of the more creative, specialized solutions. These aren't your everyday walls, but in the right situation, they’re perfect.
Gabion baskets: Stone-filled wire cages flex with minor ground movement and drain naturally, making them ideal for floodways, creek realignment, and mine haul-roads. They green over time as vegetation colonizes the voids, softening the look of heavy infrastructure.
Timber crib walls: Interlocking, pressure-treated timber frames create a rustic façade prized that works great in parklands and on golf-courses. They’re lightweight, have a low embodied-carbon footprint, and infill with free-draining stone for stability.
Soil-nail and shotcrete walls: For over-steep cuts or basement shoring, a grid of tensioned steel bars is drilled into the ground, then strengthened with reinforced shotcrete. This method preserves valuable real estate because the finished wall is super thin, often less than 300 mm.
Hybrid toe-gravity and geogrid backfill: When toe room is scarce but height is substantial, we sometimes pour a short gravity toe at the base to counter sliding and then reinforce the upper backfill with geogrids. This allows us to trim concrete volume while keeping wall performance high.
We always run a full stability analysis on these, of course. Just because a solution is creative doesn't mean we get to skip the math. To be fair, a lot of clients come to us with an aesthetic in mind, and our job is to figure out how to build it so it’s not just beautiful, but also incredibly safe.
Planning a unique façade? Browse our architectural retaining wall finishes or request a consultation with the Exactus Design team.
How Exactus’s engineers choose the ideal wall
It would be easy if we could just plug some numbers into a computer and have it spit out the "perfect wall." But it's never that simple. Choosing the right design is this blend of hard science, gut feeling from years of experience, and just knowing the local ground. Our whole process is really about taking a thousand different variables and boiling them down to a handful of solid options for you.
Here’s how we do it:
Site reconnaissance and data capture: We document topography, drainage paths, utility corridors, and any signs of slope instability, then commission targeted geotechnical borings to understand the soil.
Load definition: We quantify, measure and define everything, from active and passive earth pressures, groundwater levels and traffic surcharges to seismic coefficients and planned architectural loads.
Concept filtering: Using our in-house decision matrix (which measures factors like cost, constructability, aesthetics and embodied carbon), we narrow the options down to the two or three wall types that most suit the brief.
Detailed modelling: Finite-element checks verify sliding, overturning, global stability, facing pull-out, and long-term deflection. Drainage, erosion control, and back-of-wall waterproofing are integrated at this stage, as opposed to being tacked on when it’s too late.
Permitting and tender support: All of our plans carry our structural stamp, and we support you throughout the lifecycle of the project. That means we’ll liaise with county engineers, review contractor RFIs, and stay engaged until the wall passes final inspection.
Want to know more about us? Click here to meet our structural engineers and geotechnical specialists.
From Consultation to Completion
We know this process can feel overwhelming. So we’ve mapped it out to be as straightforward as possible. No jargon, no surprises. This is what it actually looks like to work with us from start to finish.
Here’s what that looks like:
Step 1: Discovery call and photo review: Send us site photos, a rough grading plan, the height the wall needs to be and your style wishlist. We’ll look for any red flags and outline the scope of the survey and soil testing.
Step 2: Concept and budget alignment: You’ll receive a concise options brief within ten working days. That will cover wall type, preliminary sketches, projected costs, and a timeline for the construction. You choose the direction; we refine the details.
Step 3: Final design and construction support: At this point we’ll issue a full structural package that’s ready for contractor bids and which covers wall geometry, reinforcement schedules, drainage details, material specifications and more. We perform milestone inspections and issue field reports during construction so that builders stay on spec.
Step 4: Completion and certification: A final walk-through confirms quality workmanship and ensures that drainage and safety factors have been effectively dealt with. We then issue a compliance certificate plus a maintenance guide to protect your investment for the decades to come.
Ready to move from concept to reality? Reach out to us today for a no-obligation slope review, and let’s secure your site the Exactus way.
Summary and Next Steps
It’s funny. You spend years studying geomechanics and finite element analysis, and at the end of the day, what you’re really doing is giving someone a flat, usable backyard. Or making sure a road doesn’t wash away in the next big rain. You’re holding back the chaos, just a little bit, so people can have a safe place to live or work.
There's a quiet weight to that responsibility. You stand on a site, looking at a steep, muddy slope, and you have to visualize the forces at play—the water, the soil, the weight of everything. And then you have to translate all of that into a set of drawings that a contractor can build. A structure that has to be perfect, because the consequences of it not being perfect are just too high. It’s more than concrete and steel. It’s peace of mind. It’s knowing that what you built will stand, long after you’ve walked away. And that feeling… well, that’s why we do this.
Get your Tailored Retaining Wall Solution —Book a Slope Evaluation Today! With Exactus Engineering. Secure, stamped plans for safe installation.
Your Questions Answered
Q. Which wall type best suits a sloped backyard?
It depends on the steepness of the slope, the condition of the soil and the available space. Gravity and MSE walls are common for moderate slopes, while anchored or cantilever walls can be required for taller or tighter spaces. Our engineers will assess your site and recommend the safest, most cost-effective option.
Q. Is drainage always required behind retaining walls?
Yes, proper drainage is critical. Without it, water pressure can build up behind the wall, leading to cracks, bulges, or total failure. Drainage solutions like gravel backfill, weep holes, and drain pipes are integrated into every Exactus design.
Q. Can I build a retaining wall myself?
That depends on how tall it needs to be! It’s not uncommon for people to build their own small walls of under a meter in height. However, taller or load-bearing walls require engineering plans and permits. That’s why Exactus provides code-compliant designs and oversight for safe, legal construction that lasts.
Q. What’s the typical timeline and cost?
Timelines range from 2–6 weeks depending on complexity, size, and weather. Costs vary by wall type and material—for example, modular block walls are generally cheaper than cantilever or anchored walls. Don’t worry, though—we’ll provide upfront estimates and help to match your design to your budget.
