Retaining Wall Systems: Essential Guide to Retaining Wall Structures and Their Performance
- 07 Sketches
- May 18
- 9 min read
Updated: May 20
Introduction
As an architect or designer, choosing the right type of retaining wall is essential for both functionality and long-term performance. Retaining walls help manage changes in ground elevation and provide support to prevent soil erosion or collapse. But with so many options available—each with different materials, construction methods, costs, and lifespans—it can be challenging to decide which type best fits your project needs.
In this blog, I’ll walk you through the most commonly used retaining wall systems, explaining how they work, how long they typically last. This comparison is based on key factors like structural durability and construction expense, to help you make practical and informed decisions during the design process.
Understanding Different Retaining Wall Types: Cost vs. Lifespan
Let’s take a closer look at the various types of retaining wall systems shown in the illustration. Each type is rated based on cost and lifespan, helping you quickly assess which option might suit your project best. The orange circles indicate the level (Low, Medium, or High), with more filled circles meaning higher cost or longer life.
Rip-Rap Stone
Rip-rap stone walls are constructed by placing large, angular stones loosely along a slope. This type of retaining structure is one of the most cost-effective solutions and is often used for erosion control, especially along riverbanks or coastal areas. While the installation is simple and inexpensive, the structural integrity is moderate. Rip-rap is not ideal for supporting vertical loads but serves well in controlling surface runoff and protecting soil from water damage. Its lifespan is reasonably good, making it a practical choice for low-budget, non-critical applications.
Dry-Laid Stone
Dry-laid stone walls are made by carefully stacking stones without using mortar. This method gives a natural, traditional aesthetic and is often preferred in landscape design and terracing. The cost is moderate due to the labor involved in precise stone placement. However, these walls allow natural drainage and can shift slightly with ground movement without collapsing, which adds to their durability. With proper site preparation and maintenance, dry-laid stone walls can last for decades, offering both charm and resilience.
Placed Stone
Placed stone retaining walls involve the use of carefully arranged stones, often with mortar or concrete foundations to ensure structural stability. These walls are typically more engineered than dry-laid ones and are designed to handle greater loads. The cost is relatively higher due to materials and labor, but the result is a strong, long-lasting wall with a refined appearance. Placed stone walls are ideal for both functional and decorative purposes, offering a balance of aesthetics and performance.
Gabions
Gabion walls are formed using wire mesh cages filled with rocks or rubble. These structures are particularly effective for sites with high water runoff, as they allow excellent drainage while resisting erosion. Gabions are moderately to highly priced, primarily due to the materials and installation process, but they offer a high lifespan and minimal maintenance. Over time, gabion walls can even become more stable as vegetation grows between the rocks, integrating them with the landscape. They're widely used in civil engineering and slope stabilization projects.
Cast Concrete
Cast concrete retaining walls are among the strongest and most durable options available. These walls are poured on-site using formwork and reinforced with steel bars for additional strength. Although the cost is high, cast concrete walls offer a very long service life and are capable of handling significant loads. They are ideal for large infrastructure projects, retaining steep or heavy soils, and creating clean, modern design lines. Their performance in both structural support and longevity makes them a top-tier choice in demanding conditions.
Cribbing
Crib walls are built using interlocking structural elements—typically wood or precast concrete—that form open cells filled with granular material. These walls offer decent structural performance and are moderately priced. One of their main advantages is permeability, which allows water to drain through the wall, reducing hydrostatic pressure. However, wooden crib walls may degrade faster over time compared to concrete alternatives. Cribbing is a good choice for moderate slopes and projects where appearance and drainage are important considerations.
Root Reinforced (Log Walls)
Root-reinforced or log retaining walls use timber logs driven horizontally into the slope, often in combination with vegetative support. This method is low in cost and environmentally friendly, making it popular for small-scale, rural, or temporary solutions. However, the durability of wood in contact with soil is limited, and these walls tend to have a shorter lifespan unless treated and maintained regularly. They work best in low-pressure areas or as part of green infrastructure that promotes natural stabilization over time.
Cantilever Wall
Cantilever retaining walls are engineered concrete structures that use leverage to resist soil pressure. The wall extends downward into a base slab, which anchors it firmly into the ground and counteracts the lateral forces acting on it. This type of wall is highly effective and long-lasting, though it comes with a high construction cost due to its complexity and the need for reinforcement. Cantilever walls are commonly used in urban developments, highways, and large-scale retaining systems where strength and space efficiency are critical.
Case Study: Gabion Retaining Wall
Project: Port Moresby, Papua New Guinea
The project was to construct a multi-million-dollar residence that overlooks Idlers Bay on top of a steep sloping block in Port Moresby, Papua New Guinea. To provide this multi-levelled home with a solid foundation for build, an 8-metre-high gabion retaining wall had to be constructed. The client was looking for an economical retaining wall solution that will support the house and have a natural, aesthetic finish to blend in with its surrounding.
Upon inspection, the site was deemed unsuitable for build due to its irregular foundation. The site had to be excavated 7 metres deep to provide a level platform for the construction of the gabion baskets. A total of 155 gabions were installed and filled with rocks sourced from the site to construct an 8m high by 52m long retaining wall which was further reinforced using Ten Cate Miragrid GX Geogrid.
To achieve the client request for a retaining wall with a natural finish, 2m x 60m rolls of Grassroots Synthetic Erosion Control Mats were installed between each layer of gabion. Grassroots will help to encourage the growth of vines around the gabion baskets, resulting in a green vegetated wall.
Key Retaining Wall Types Based on Structural Design and Function
Piling Wall
Piling walls are vertical structural elements driven deep into the ground to resist the lateral pressure of soil. This type of wall is commonly used where space is limited or excavation is difficult. The depth of the pile ensures stability by using the soil's resistance to lateral movement. Piling can be constructed using concrete, steel, or even timber, and is often part of temporary or deep excavation support systems. It’s a go-to solution in urban construction or near existing structures.
Rear Anchored Wall
Rear anchored retaining walls are reinforced by cables or rods that are anchored into the soil or rock behind the wall face. These tensioned elements help resist forward pressure and allow the wall to retain larger volumes of earth or water. This design is often used in steep or heavily loaded conditions where other types might not be feasible. It works well in conjunction with sheet piles or gravity walls, combining anchoring with structural mass to enhance performance.
Concrete Structure Against Retaining Wall
This type involves a structural wall made of concrete being supported by an adjacent retaining wall or being part of the retaining wall system itself. It’s commonly seen in basement construction where the retaining wall also acts as a structural wall. This dual-purpose design saves space and material while maintaining structural integrity. It's especially effective in urban construction where space and structural integration are key considerations.
Gravity Wall
Gravity walls rely solely on their own weight and mass to resist the pressure from the retained soil. Built using concrete, stone, or other dense materials, these walls are thick and stable. They don’t usually require reinforcement, making them simpler to construct in low-rise applications. Gravity walls are best suited for low to medium height retaining conditions and are widely used in landscaping and small infrastructure projects.
Built into Structure
This approach integrates the retaining wall directly into a building or constructed feature, such as a basement wall or foundation system. By doing so, the wall serves dual purposes—retaining soil and supporting the structure above. It’s a highly efficient solution for buildings constructed on sloped terrain, optimizing material use and minimizing the need for separate retaining systems. These walls are usually reinforced concrete for maximum strength and performance.
Heel and Toe (Cantilevered Base)
This refers to a cantilever retaining wall that features an extended base slab with a “heel” (extending under the retained soil) and a “toe” (extending in front of the wall). The design provides stability through leverage—the weight of the backfill on the heel helps counteract the overturning forces of the retained soil. This is a common and effective design used in cantilever walls, offering both strength and economic use of materials for taller retaining walls.
Case Study: Gravity Retaining Wall
Project: The Carnegie at Washingtonian Center, USA
Overview: Magnum Stone gravity walls were utilized to support a seven-story senior living facility.
Details: The project showcased the efficiency of gravity walls in large-scale developments, providing robust support while optimizing land use. The modular design facilitated rapid construction and adaptability to site conditions.
The Carnegie at Washingtonian Center is a massive seven-story senior living complex located in Gaithersburg, MD, USA. This robust development is home to a 450,000 sq. ft. retirement community with independent living, assisted living and memory care. The project’s goal was to maximize this hillside commercial property’s development potential.
Built on a hillside property, the retaining walls played a vital role in extending buildable land with space-efficient reinforcement. The largest wall stands at 26 ft. (7.9 m.) high with a minimal base depth of Stone’s interlocking blocks and extender units. The gravity extenders allowed more flexibility to build closer to structures and property lines, which alternatives could not. Geogrid reinforced walls were not a viable option for this project due to the development’s limited excavation area.
The five gravity walls efficiently convey stormwater and minimize excavation depths to optimize land and building closer to critical infrastructure. From curves to tall walls, the system’s gravity wall extenders securely handle challenging design considerations of these wide-ranging retaining wall applications.
The retaining walls maximized buildable space for the senior living facility with strong, reinforced gravity walls. The gravity extenders’ reinforcement achieved the commercial development’s design objectives with long-lasting, space-efficient and timeless looking retaining walls.
Understanding the Typical Brick Mass Retaining Wall
The typical brick mass retaining wall is a simple yet effective solution used for retaining soil, especially in landscape and garden-level constructions. This type of wall relies primarily on its weight and mass to resist the lateral pressure of the soil behind it. Let's walk through its key structural components and functions:
This type of retaining wall is commonly used for small to medium-height soil retention applications, such as garden beds, landscaping steps, or boundary demarcations where moderate lateral soil pressure is expected. It is a cost-effective and aesthetically pleasing option, especially where traditional brickwork matches the surrounding architecture.
1. Precast Concrete Weathered Coping Stone
At the top of the wall sits a precast concrete coping stone, which is weathered (angled) to allow rainwater runoff. This element helps protect the top of the brick wall from direct exposure to water, minimizing erosion and water infiltration.
2. DPC (Damp Proof Course)
Directly beneath the coping stone is the DPC layer. The Damp Proof Course acts as a moisture barrier, preventing ground moisture from rising into the wall. This is essential for enhancing the durability of the bricks and mortar.
3. Brick Wall Structure
The wall itself is constructed using standard-size bricks, arranged in a solid mass. It is 1800 mm tall, with part of it (450 mm) below the front ground level to anchor the structure. The wall is 840 mm wide at the base to ensure stability and strength, tapering slightly towards the top.
4. Weep Holes for Drainage
One of the most crucial features in a retaining wall is the drainage system. This wall includes 75 mm diameter weep holes, spaced appropriately, with PVC piping used to line them. These weep holes are placed approximately 525 mm above the footing level and allow for the release of hydrostatic pressure by letting trapped water behind the wall escape. Proper drainage prevents water buildup, which could otherwise destabilize the wall.
5. Rubble Filling Behind the Wall
Behind the retaining wall is a 900 mm thick layer of rubble filling, placed to support drainage. This loose stone material facilitates the flow of water toward the weep holes, enhancing the efficiency of the drainage system.
6. Mass Concrete Foundation
The base of the wall rests on a mass concrete foundation, which provides the necessary strength and stability to hold the wall in place. The foundation is 840 mm wide and 300 mm deep, ensuring the wall can bear the soil's load and prevent settling or tilting over time.
7. Dimension and Ground Levels
The wall rises 1800 mm above the footing, with 450 mm below ground level in front.
The total height of the wall is distributed across multiple segments, including 900 mm of backfill soil height and a 225 mm step-up for the base.
The front ground level is also clearly marked to ensure accurate construction in site conditions.
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