Retaining walls serve multiple purposes in outdoor spaces. They hold back soil, prevent erosion, and create level areas in sloped yards. Whether you’re looking to improve the look of your yard or solve drainage issues, retaining walls can be a great solution. This guide will explore retaining wall types, materials used, design principles, and practical considerations to help you make an informed decision for your landscaping project.
Purpose and Function of Retaining Walls
Retaining walls are outdoor structures that hold back soil and create flat, usable spaces in sloped areas. They serve three main functions: preventing soil erosion, leveling terrain, and managing water drainage. These walls stop soil from washing away during heavy rains or other weather events. They’re useful in yards with significant slopes or varying elevations, as they can create stable, flat ground for patios, gardens, or play areas.
Retaining walls also play a crucial role in water management. Many incorporate drainage systems such as French drains, perforated pipes, and weep holes to control water flow and prevent excess moisture from eroding the surrounding soil. This feature is important in areas with heavy rainfall or poor natural drainage.
Types of Retaining Walls
There are several types of retaining walls, each suited to different landscapes and purposes. The type you choose depends on location, soil type, required drainage, structural support needs, and desired design. Below, we cover the four main types of retaining walls.
Gravity Retaining Walls
Gravity walls are the simplest type of retaining wall. They rely on their own weight and mass to hold back soil pressure. These walls are typically up to 3 feet tall. Gravity walls don’t require additional reinforcement, making them ideal for smaller projects and DIY enthusiasts. Materials like concrete blocks, natural stone, or even large boulders can be used to construct gravity walls.
Cantilever Retaining Walls
Cantilever walls are more complex structures that use a reinforced concrete base to distribute the weight of the retained soil. The wall and base form an inverted T-shape, with the vertical section resisting the pressure of the soil behind it. These walls are more efficient than gravity walls and can be built taller, making them ideal for larger landscaping projects. Cantilever walls require professional design and installation because of their structural complexity.
Anchored Retaining Walls
Anchored retaining walls use additional support systems to hold back soil pressure. These walls have anchors, typically made of steel cables or rods, that extend deep into the soil behind the wall. The anchors are secured to a stable layer of rock or soil, providing extra strength to the wall. This type allows for thinner wall construction and is ideal for retaining large amounts of soil or in areas with limited space. Anchored walls are often the most cost-effective option for tall retaining structures.
Gabion Retaining Walls
Gabion walls are made of wire mesh baskets filled with rocks, concrete, or other heavy materials. These walls are highly permeable, making them a good choice for areas with drainage issues. Gabion walls have a rustic, natural appearance and can blend well with outdoor environments. They’re particularly useful in erosion control projects and can be built relatively quickly. However, they may require more maintenance over time as the fill material settles.
Choosing the Right Material for Your Retaining Wall
Choosing the right material for your retaining wall impacts both style and function. The retaining wall materials you choose will impact the wall’s durability, appearance, and cost. Here are some popular options.
Wood Retaining Walls
Wood is an affordable and attractive option for retaining walls. It’s easy to work with for DIY projects. Pressure-treated lumber or naturally rot-resistant woods like cedar or redwood are best for longevity. However, wood retaining walls typically have a shorter lifespan compared to other materials and may require more frequent maintenance.
Concrete Block Retaining Walls
Concrete blocks are durable, versatile, and available in many styles and colors. They’re relatively easy to install and can be used for both straight and curved walls. Interlocking concrete blocks are popular for their stability and ease of installation. While more expensive than wood, concrete block retaining walls offer better longevity and require less maintenance.
Natural Stone Retaining Walls
Natural stone retaining walls offer a timeless, elegant appearance. They blend well with natural landscapes and can increase property value. Options include fieldstone, granite, and limestone. While beautiful, natural stone walls can be more expensive and may require professional installation due to their weight and complexity.
Brick Retaining Walls
Brick retaining walls provide a classic, refined look that complements many architectural styles. They’re durable and low-maintenance but can be more costly than other options. Due to the skill needed for construction and the importance of a solid foundation, brick walls typically require professional installation.
Retaining Wall Design Principles
Proper design ensures the stability and longevity of your retaining wall. Consider these key principles as you decide how you want your retaining wall to be incorporated into your landscape design.
Height and Thickness Considerations
The height of your retaining wall affects its design and construction method. Generally, walls less than 4 feet tall can be simple gravity walls, while taller structures require more complex engineering. The wall’s thickness should increase with its height to withstand greater soil pressure.
Check local building codes, as permits may be required for walls over a certain height. Many jurisdictions require permits for walls over 4 feet tall or those supporting a significant load. Building codes in your area may affect the height of your wall, the structural reinforcements, and even the materials you can use.
Drainage Solutions
Proper drainage prevents water buildup behind the wall. Incorporate a drainage system, such as a perforated pipe wrapped in landscape fabric and surrounded by gravel, at the base of the wall. This allows water to move away from the wall, reducing pressure and potential damage.
Soil Pressure Management
Different soils exert varying amounts of pressure, which affects wall design. Clay soils, for example, retain more water and exert more pressure than sandy soils. In some cases, geotextile fabrics or reinforcement grids may be necessary to distribute soil pressure more evenly.
DIY vs. Professional Retaining Wall Installation
Deciding between DIY and professional installation depends on several factors. Small, simple walls under 3 feet tall can often be a DIY project if you have the necessary skills and tools. However, taller walls, those installed on challenging terrain, or walls requiring complex drainage solutions are best left to professionals. Consider your experience, the project’s complexity, and local building codes when making this decision.
Learning how to build a retaining wall can be a rewarding project for DIY enthusiasts. This type of wall is relatively simple to construct and can be a good starting point for those new to retaining wall construction.
Retaining Wall Costs
According to Angi, retaining walls cost between $3,202 and $9,203, with most people paying about $6,065. However, the cost can vary significantly depending on the materials, labor, and site preparation you include in your design.
Material Costs
Material costs can range from $5 to $200 per square foot. Vinyl is typically the cheapest option, while natural stone and steel tend to be the most expensive. Concrete blocks offer a mid-range price point with good durability.
| Wall Material | Average Cost per Square Foot |
| Vinyl | $10–$15 |
| Railroad Ties | $25–$30 |
| Timber | $15–$30 |
| Brick | $20–$25 |
| Rammed Earth | $20–$25 |
| Gabion | $10–$40 |
| Stone | $20–$100 |
| Concrete | $30–$50 |
| I-Beam | $40–$90 |
| Steel | $15–$150 |
Labor Expenses
Building smaller retaining walls yourself can save you $15 to $50 per square foot in labor costs, which translates to $600 to $2,000 in savings for a wall that’s 20 feet long and 2 feet high. However, the costs of material delivery or renting a vehicle for transporting heavy materials might offset these savings.
We recommend hiring a professional mason for more complex walls, like a cantilevered wall designed to hold back significant weight. Additionally, if your wall is taller than 4 feet, you’ll need to contact a local structural engineer because it requires more complex structural support.
Hiring a landscaper for your retaining wall project can cost between $50 to $100 per hour, and the project might take a couple of days, though interlocking blocks are quicker to install. While DIY labor can be cost-effective for small walls without heavy materials, walls taller than 4 feet or those lacking proper installation and drainage can fail easily, which can eliminate the savings of doing it yourself. Hiring a professional installer is sometimes the best option when it comes to structural integrity and proper construction.
Site Specific Fees
Where you build your retaining wall can significantly impact the cost of the project. If the ground is sloped, it can increase labor costs by 50% or more, depending on how much extra work is required. Building a retaining wall in a traditional yard might only cost $5–$200 per linear foot, but due to the added challenges, a shoreline retaining wall could cost anywhere from $150–$600 per linear foot.
Site Preparation Fees
The building of the wall isn’t the only part of the project that could be costly. You have to properly prep the site before building in order to ensure the structure is secure and will be long-lasting. These are some of the costs associated with preparing the site.
- Structural engineer: $350–$750
- Land clearing: $110–$250 per hour
- Land grading: $900–$3,000
- Tree removal: $200–$2,000
Retaining Wall Maintenance and Longevity
Maintenance can extend the life of your retaining wall. Perform regular inspections for signs of wear, damage, or shifting. Clean the wall periodically to prevent mold and mildew growth, and address any drainage issues as soon as possible to prevent water damage. Concrete and stone walls can last 50–100 years with proper care, while wood walls typically last 20–40 years.
Creative Ideas for Retaining Wall Landscaping
Retaining walls can be both functional and a design centerpiece. With some creativity, you can turn a functional wall into a landscaping feature. Consider using your retaining wall to create a terraced garden or a built-in seating area or add a water feature. For a modern touch, use sleek, geometric concrete blocks or integrate LED lighting to highlight the wall’s structure at night. You can also mix materials like wood and metal for a unique, contemporary design that stands out.
Terraced Gardens
Terraced gardens, formed by a series of retaining walls, allow for flat planting areas on different levels, making it easier to grow a variety of plants in defined sections. This design helps manage water runoff and prevent soil erosion for healthier plants. You can have easy access to each level by incorporating steps or pathways between the terraces, and you can use the separation between plots to experiment with different plants, arrangements, and colors.
Built-In Seating Areas
Using a retaining wall to create a built-in seating area is another great way to combine function and style. This approach uses the structural support of the retaining wall to provide sturdy, long-lasting seating, perfect for patios, fire pits, or garden areas. By incorporating comfortable cushions and pillows, you can transform the space into an inviting spot for relaxing and entertaining guests. The built-in seating can be designed with storage compartments underneath, offering a practical solution for keeping outdoor items organized.
Water Feature Integration
Incorporating a water feature into a retaining wall is an elegant way to create the feeling of a tranquil getaway in your yard. A waterfall or cascading stream can turn your retaining wall into a focal point, creating a soothing ambiance and attracting birds and other wildlife. Using a retaining wall for a water feature allows for efficient use of space, especially in sloped areas, and can be seamlessly blended with surrounding plants and stones for a natural, cohesive look.
Common Retaining Wall Problems and Solutions
Retaining walls are essential in landscaping, but they can experience various problems over time. By addressing these common problems with the appropriate solutions, you can maintain your retaining wall’s structural integrity and longevity.
Poor Drainage
Inadequate drainage can cause water buildup behind the wall, leading to hydrostatic pressure and potential wall failure.
- Drainage pipes: Install perforated drainage pipes (weeping tiles) at the base of the wall to divert water away.
- Gravel backfill: Use gravel or crushed stone behind the wall to improve drainage.
- Weep holes: Incorporate weep holes in the wall to allow water to escape.
Erosion
Soil erosion can undermine the integrity of the retaining wall.
- Erosion control fabrics: Use erosion control fabrics or mats to stabilize the soil.
- Proper Grading: Ensure the surrounding area is graded properly to divert water away from the wall.
- Vegetation: Plant ground cover or shrubs to help hold the soil in place.
Bulging or Leaning
Retaining walls might bulge or lean outward due to excessive pressure or poor construction.
- Reinforcement: Reinforce the wall with tiebacks or anchors that extend into the soil behind the wall.
- Rebuilding: In severe cases, dismantle and rebuild the wall with proper engineering and construction techniques.
- Terracing: Consider terracing steep slopes to reduce the pressure on a single wall.
Cracking
Cracks can develop in the retaining wall due to settling, temperature changes, or pressure.
- Control joints: Incorporate control joints in concrete walls to allow for expansion and contraction.
- Flexible materials: Use flexible materials like segmented concrete blocks that can move slightly without cracking.
- Seal cracks: Fill small cracks with concrete sealant or epoxy to prevent water infiltration.
Foundation Issues
Sometimes, a retaining wall’s foundation is unstable, leading to settling or shifting.
- Compacted base: Use a well-compacted gravel base to provide a stable foundation.
- Proper footing: Ensure the wall has a solid footing, extending below the frost line for stability.
- Professional consultation: For serious foundation issues, consult a structural engineer for proper assessment and repair.
Material Deterioration
The materials used in the retaining wall can degrade over time, reducing its effectiveness.
- Durable materials: Use durable, weather-resistant materials such as concrete blocks, stone, or treated timber.
- Protective coatings: Apply protective sealants or coatings to materials prone to weathering.
- Regular maintenance: Inspect the wall regularly and replace deteriorating materials promptly.
Soil Settlement
The soil behind the wall may settle unevenly, causing gaps or uneven pressure.
- Compaction: Properly compact the backfill soil in layers during construction.
- Geogrid reinforcement: Use geogrid or other soil reinforcement materials to stabilize the backfill.
- Monitoring: Monitor the wall and backfill regularly for signs of settlement and address issues promptly.
Vegetation Growth
Tree roots or other vegetation can grow into and destabilize the wall.
- Appropriate planting: Choose plants with non-invasive root systems near the wall.
- Regular trimming: Keep vegetation trimmed and away from the wall.
- Root barriers: Install root barriers to prevent roots from penetrating the wall.
Inadequate Design
This issue is when the wall wasn’t designed to handle the specific conditions of the site.
- Professional design: Consult with a landscape architect or engineer to design a wall suitable for the site’s conditions.
- Load calculations: Ensure the wall is designed to handle the expected load, including soil pressure and any additional loads, such as vehicles or structures.
Frost Heave
Freezing and thawing cycles can cause the soil to expand and contract, leading to wall movement.
- Frost-proof footing: Extend the footing below the frost line to prevent frost heave.
- Proper drainage: Ensure good drainage to reduce the water content in the soil behind the wall and minimize frost heave.
