Retaining walls serve both functional and aesthetic purposes in many yards. Building a straight retaining wall is straightforward, but constructing corners presents unique challenges. The right approach makes all the difference in creating a sturdy, attractive retaining wall that stands the test of time.
Our guide will walk you through building retaining wall corners, from material selection to step-by-step instructions for various corner types. We’ll help DIY enthusiasts tackle this project confidently, saving time and money while making their yards look great.
Types of Retaining Wall Blocks and Their Impact on Corner Construction
The type of retaining wall block greatly influences how you construct corners. Different blocks offer varying levels of flexibility and ease when building corners.
One-Sided Blocks
One-sided blocks are popular for retaining walls due to their versatility and ease of use. These blocks typically have a textured face on one side and a lip at the back that interlocks with the row beneath it.
When working with one-sided blocks, it’s important to plan the layout carefully. Outside corners with one-sided blocks are often gracefully curved rather than sharp 90-degree angles to accommodate the block’s structure. You can construct inside corners at 90 degrees, though you need meticulous planning for proper interlocking and stability. Wedge-shaped one-sided blocks allow for smoother curved designs.
Corner Units
Corner units are a good option for a more polished look with sharp 90-degree corners. These specialized blocks work seamlessly with standard retaining wall blocks, providing stability and a polished look.
Corner units have a finished surface on at least two sides, contributing to the wall’s clean, refined look. To retain the wall’s structural integrity, alternate the direction of these blocks with each course. This strengthens the corner and distributes weight evenly. You may need to occasionally trim standard blocks to work with the corner units.
Multisided Blocks
Multisided blocks, such as certain pavers or cinder blocks, offer flexibility in corner construction. These blocks have a finished look on multiple sides, simplifying the creation of sharp corners.
Multisided blocks’ main advantage is their stackability, which makes it easy to create corners without extensive cutting or shaping. This makes them suitable for both inside and outside corners. Their design often requires minimal modification, making them an attractive option for DIY projects.
Building Outside Corners
Outside corners are often the most visible part of a retaining wall. The look of these corners affects the wall’s durability and visual harmony with the landscape. Your approach will depend on the type of block you use.
Curved Outside Corners With Wedge-Shaped Blocks
Creating a curved outside corner is often the most aesthetically pleasing and structurally sound option when working with wedge-shaped blocks. These blocks form gentle, flowing curves that align well with natural landscapes.
To build a curved outside corner, begin by laying out the desired curve using a flexible material such as a garden hose or rope. This visual guide keeps the curvature even and helps you determine the correct dimensions. As you place each block along the curve, make sure each one nestles against the previous for stability. You may need to adjust the radius for a cohesive look. Use a level to maintain uniformity across the structure horizontally and vertically.
Sharp 90-Degree Outside Corners
Use specialized corner units or multisided blocks for a crisp, 90-degree outside corner. These blocks are tailored to create precise angles.
To construct a sharp outside corner, start from the corner itself and work outward. Alternate the direction of corner units with every course to strengthen the overall structure. Use masonry adhesive to add another layer of security. Accurately cut standard blocks to nest tightly with these corner units and finish the look.
Building Inside Corners
While less visible, inside corners are equally important for the retaining wall’s structural integrity. Use a strategic approach to ensure the wall remains sound over time.
Ninety-Degree Inside Corners With Standard Blocks
Creating a 90-degree inside corner with standard blocks is relatively straightforward but requires attention to detail. Proper alignment and interlocking make for a stable structure.
Begin the first course at the corner, forming the foundation for subsequent rows. Each successive layer should overlap the joints beneath, maintaining a strong staggered pattern. You may need to cut blocks to accommodate the pattern. Use a level to make sure each course remains even, preventing eventual sagging or misalignment.
Inside Corners With Corner Units
Creating inside corners with corner units is similar to creating outside corners, with a focus on interlocking and stability.
Start from the corner itself and extend outward. Alternate the direction of the corner units with each course to ensure stability, and make sure these units properly interlock with standard blocks.
Special Considerations for Retaining Wall Corners
Building retaining wall corners involves more than just placing blocks. Consider these factors to ensure the longevity and stability of your wall.
Reinforcement for Taller Walls
You may need additional reinforcement for retaining walls over 4 feet tall, especially at corners. Options include installing geogrid, a synthetic material you weave through block layers to provide additional support. Alternatively, rebar and concrete filling add strength to the core of the corner units. Incorporate tie-backs or deadmen anchors to further secure the structure, especially in areas prone to soil movement or pressure buildup.
Drainage Considerations
Proper drainage is extremely important and requires special attention. If not properly managed, water accumulation can compromise the structure’s integrity.
Install drain tiles behind the wall, extending around corners to encourage water to flow away from the structure’s base. Use gravel backfill as a permeable layer that allows water to filter down to the drainage system. Weep holes at the wall’s base can also help direct water away and relieve pressure buildup.
Soil Compaction
Proper soil compaction helps prevent settling and shifting, particularly at corners where pressure can concentrate. Use a plate compactor to firmly set the base material and subsequent backfill. We recommend compacting in layers no thicker than 6 inches to ensure even pressure distribution. Pay particular attention to the areas directly behind corner units, as these spots often bear the brunt of structural stress.
Tools and Materials Needed for Corner Construction
The right tools and materials make building retaining wall corners much smoother. Essential tools include:
- Sturdy shovel and spade for digging and shaping the foundation
- Level for maintaining alignment
- Tape measure for accurate dimensions and spacing
- Hammer or mallet for adjusting blocks
- Chisel for manual shaping.
- Safety gear, including gloves, goggles, and a dust mask
Additional tools that streamline the process include a wheelbarrow for transporting materials, a string line and stakes for outlining the wall path, and a gravel rake for smoothing the base or backfill. You may need a circular saw with a masonry blade to cut blocks to size.
The materials you need largely depend on the specific project but typically include:
- Retaining wall blocks, with corner units if applicable
- Base material such as crushed stone or gravel
- Backfill
- Drainage pipe
- Landscape fabric
- Masonry adhesive.
Purchase quality materials designed to work with the material of your wall blocks.
Cutting Retaining Wall Blocks for Corners
You need to properly cut your retaining wall blocks to achieve a clean, professional look at the corners. Precise cutting helps blocks fit snugly without compromising the wall’s stability.
Accurately measure and mark the desired cut line with a pencil or chalk. We recommend using a circular saw fitted with a diamond blade for clean, precise cuts on concrete blocks. A chisel and hammer may be sufficient for softer materials, though it demands careful execution. Always wear appropriate safety gear—goggles and a dust mask—to protect from debris and dust. After cutting, smooth rough edges with a masonry chisel for a polished finish.
Maintenance and Care for Retaining Wall Corners
Retaining wall corners require ongoing maintenance to ensure their longevity and appearance. Regular upkeep prevents minor issues from escalating into major problems.
Inspect your retaining wall periodically for signs of shifting or settling. Keep corners clean to prevent debris buildup, maintain their appearance, and facilitate drainage. Address drainage issues promptly to avoid long-term damage. Reapply sealant as recommended by your block manufacturer—typically every few years—to extend the life of your wall.
Further Information
- How to Build a Stackable Block Retaining Wall (article)
- How to Align Blocks in a Curved Retaining Wall (article)
- How to Cut and Install Retaining Wall Topper Stones (article)
- Build a retaining wall with an outside 90 degree wall (wonderhowto.com)
FAQs About Building Retaining Wall Corners
Retaining walls serve several important purposes in landscaping and construction. They hold back soil on sloped terrains to prevent erosion and landslides, increase usable land for gardening or other structures, and manage water runoff to prevent flooding. They can provide structural support, and property line definition, and are even used for aesthetic reasons.
To install a retaining wall, you’ll need a shovel and spade, level, tape measure, a hammer, or mallet, a chisel, and safety gear. Helpful tools include a wheelbarrow to move the heavy blocks and supplies, string line and stakes, and a gravel rake.
Cutting retaining wall blocks for corners is an important skill for creating a clean, professional-looking finish. Start by measuring and marking the cut line on the block with a pencil or chalk. For outside corners, you’ll typically cut at a 45-degree angle. For inside corners, you may need to cut two blocks to fit together.
For concrete blocks, use a circular saw with a diamond blade or a masonry saw. For softer materials like landscape blocks, a chisel and hammer method will likely work. You should always wear safety goggles, a dusk mask, and hearing protection when cutting materials.
Place the block on a stable surface, and if using a power saw, set the depth to slightly more than the thickness of the block. If using a power saw, guide the saw along the marked line. If using a chisel, score along the cut line deeply, then use controlled strikes to split the block.
You can use a masonry chisel to clean up any rough edges left behind, and then test the piece to make sure it fits.
