Building a Retaining Wall

Building a Retaining Wall: Introduction

Building a retaining wall are a great way to enhance your landscape and gain some usable space in your yard. A retaining wall holds back soil on sloped terrain or areas where you want to create different elevation levels. Retaining walls serve both functional and decorative purposes, preventing soil erosion and creating beautiful garden beds or terraces. They can be used for driveways, patios, planters, or simply as decorative features.

Building a retaining wall range from small and simple DIY projects to large engineered walls for hillsides. The type of wall you choose depends on factors like the slope, soil conditions, height and overall look you want. With good planning and preparation, building a retaining wall is totally doable.

In this post, I’ll share everything you need to know to build your own retaining wall based on my years of experience in landscaping. We’ll cover planning considerations, material options, wall designs, construction steps, and finishing touches. By the end, you’ll have the knowledge to create a functional, attractive retaining wall that enhances your outdoor living space for years to come.

Building a Retaining Wall: Planning Your Retaining Wall

I always recommend thoroughly planning before embarking on any retaining wall project. Proper planning will help ensure your wall is structurally sound, aesthetically pleasing, and built to last. Considering the height, length and exact location are crucial first steps.

The height of your retaining wall will significantly impact the overall structural design. Generally, walls over 4 feet high require engineered plans for optimal strength and stability. Think about the elevation change you need to retain, and add at least 6 inches to account for buried footings.

Carefully lay out the wall length to accurately retain your desired space. Measure the slope length and allow an extra foot at each end for proper anchoring. Consider existing elements like trees, utilities, structures and property boundaries that may impact placement.

Accounting for drainage and soil conditions is also imperative in planning. Evaluate drainage flow on the slope to determine optimal design and need for integrated drainage components. Assess your existing soil structure through testing. Building a retaining wall require very firm, compactible backfill to withstand lateral earth pressure. Your soil evaluation will inform material choices.

Invest time upfront plotting, planning and building a retaining wall . This will pay off tremendously in achieving a functional, lasting finished product. Let the intended site usage, aesthetic goals and your budget guide decisions – with safety and longevity at the forefront. Successful execution requires a thoughtful plan tailored to your unique space.

Building a Retaining Wall: Choosing Materials

When building a retaining wall, you have several options for materials. Some of the most common choices include:

Concrete

Concrete is a popular choice when building a retaining wall . It is extremely strong and durable. Concrete walls can be poured on site or constructed from precast blocks.

Pros:

• Very strong and long-lasting
• Can be shaped however you want
• Provides a clean, modern look

Cons:

• More expensive than other materials
• Requires professional installation
• Can crack over time

Concrete Masonry Units

Concrete masonry units (CMUs) or blocks are an affordable and easy retaining wall material. They interlock and stack like bricks.

Pros:

• Budget-friendly option
• Easy for DIY construction
• Many styles and colors available

Cons:

• Not as strong and weather-resistant as poured concrete
• Can shift and settle over time

Wood

Wood is a natural-looking choice when building a retaining wall . Options like timber and railroad ties can create an attractive, rustic aesthetic.

Pros:

• Affordable and accessible
• Relatively easy to build yourself
• Variety of looks from rustic to refined

Cons:

• Requires regular maintenance and sealing
• Can warp or rot over the years
• Not as sturdy or long-lasting as concrete

No matter which material you choose, make sure to consider cost, appearance, longevity, and difficulty of installation. Consult with a landscaping professional to determine the best option for your specific needs. Proper construction and drainage are key to building a secure, lasting retaining wall.

Foundation and Footings

A proper foundation is crucial to building a sturdy, long-lasting retaining wall. Many retaining wall failures can be traced back to inadequate footings or base preparation. The footing provides a flat and level surface for the first course of blocks to be placed on. It must be sized and buried deep enough to evenly distribute the weight of the retaining wall and soil behind it, withstand frost heave forces, and avoid undermining from erosion.

When planning your footing, there are two key factors to consider – depth and width. Most retaining walls do well with a footing that extends 24-30 inches below ground level. Building a retaining wall deeper than the frost line in your region helps prevent frost heave, where freeze/thaw cycles can push up and displace the base. Wider is also better to disperse pressure along a broader area. As a rule of thumb, the footing width should be at least half to 2/3 the height of the total wall. For example, a 4 foot high wall would need a 2-3 foot wide footing.

Proper soil compaction is also critical for maximum stability. The base material under the footing should be compacted to 95% of its maximum density, according to testing protocols. Compaction helps prevent settling and consolidation after construction.

Some other footing tips for building a retaining wall :

• Use coarser gravel or crushed stone aggregate for drainage
• Incorporate steel rebar for reinforcement
• Step down footings on slopes for a level base

With care taken on the foundation and footings, your retaining wall will get off to a great start! Don’t shortcut this important first step.

Wall Design

When designing your retaining wall, you have several options to choose from depending on your needs and preferences. The most common wall designs are straight, curved, and tiered walls.

Straight Walls

Straight retaining walls are the simplest design. They are often used for level or gently sloping yards where you need the wall to retain short vertical drops under 3 feet. Straight walls can be built as gravity walls using materials like stacked stone or concrete blocks that rely on weight and mass to stay upright. For taller walls, geogrid reinforcement is recommended.

Straight walls work well for edging flower beds, tree rings, and creating terraces in your yard. They have a clean, linear look that defines and borders spaces nicely.

Curved Walls

Curved retaining walls create a softer, flowing aesthetic in your landscape. They can be used to terrace yards with rounded edges or to surround tree rings and planting beds. Curved walls require more planning and precision than straight walls, as the curve needs to be laid out accurately and the blocks or stone cut to fit the radius.

Reinforced soil techniques using geogrid are necessary for most curved walls above 2-3 feet high to strengthen the soil mass. Use larger radii for taller curved walls above 4 feet to improve stability. Proper drainage and gravel backfill are also critical components.

Tiered Walls

Tiered retaining walls feature two or more short, straight walls stacked on top of each other and set back to create a terraced effect. They are useful for sloped yards where you need to make level planting areas. The setback between walls provides room for plants and helps distribute the soil pressure more evenly.

Tiered walls require geogrid reinforcement between each wall section to tie them together into a cohesive, stable structure. Proper drainage between tiers is also important to prevent water buildup and pressure on the lower walls. The walls can be made of various materials like concrete, natural stone, or blocks.

Reinforcement Recommendations

For walls above 3-4 feet in height, reinforcement is recommended to improve stability. Geogrid fabric offers the most effective reinforcement for all wall shapes. Geogrid is layered within the compacted gravel backfill to connect the wall facia with the soil behind it. This creates a reinforced soil mass that withstands lateral pressure from the slope.

For mortared block or rock walls, steel rebar can also be used to reinforce tall sections. Include weep holes at the base of the wall to allow water drainage and prevent hydrostatic pressure on the wall. Proper reinforcement and drainage will ensure your retaining wall lasts for many years!

Building Your Wall

Once your foundation and footings are in place, you’re ready to start building a retaining wall . Proper construction technique is critical to ensure structural integrity and prevent issues down the road. Here are some step-by-step tips:

Level Your Base Course

• Place your first course of blocks on the prepared base. Use a 4-foot level on top of blocks to ensure they are perfectly level.
• Level front-to-back and side-to-side. Shim underneath blocks as needed to level.
• Double check corners and junctions where blocks meet for any high or low spots. Adjust as needed.
• String lines can also help keep courses straight and level.

Use Proper Cornering Technique

• Alternate overlapping blocks at corners and curves. This strengthens the wall and prevents seams from lining up vertically.
• Cut partial units as needed to stagger joints. A concrete saw or masonry chisel can be used for straight cuts.
• Use corner blocks designed for retaining walls when available for a tight fit.

Install Drainage

• Place perforated drainage pipe behind first course, with an outlet to daylight. Backfill with gravel.
• Additional drainage material such as gravel or drainage matting can be used every few courses.
• Weep holes in wall units can help relieve water pressure.

Stack Additional Courses

• Sweep top of units clean before setting next course. Use a 4-foot level to ensure each course is level.
• Stagger blocks to bridge vertical joints between courses.
• Interlock blocks tightly without excessive gapping. Shims or small drainage material can help fill smaller gaps.
• Use mason’s string or a story pole to check batter setback and alignment.
• Glue may be used for added stability, following manufacturer instructions.

Compact Backfill

• Fill behind wall with drainage aggregate, compacting every 6-12 inches. Use hand tamper for best results.
• Don’t over compact and squeeze out drainage material. Compact to 95% Standard Proctor density.
• Use approving backfill material – avoid heavy clays.

Let me know if you would like me to expand on any part of this section further. I aimed to provide an authoritative, trustworthy step-by-step guide based on expertise.

Building a Retaining Wall: Backfill and Grading

Proper drainage and backfill are crucial to the success and longevity of your retaining wall. The backfill is the material that fills the space behind the wall between it and the soil it is retaining. Grading refers to achieving the proper slope of the backfill material away from the wall.

You want the backfill to be porous material like gravel, not clay or heavy compacted soil. This allows for drainage so water does not pool behind the wall and cause pressure. The backfill should be placed in layers or lifts of around 6-8 inches and compacted after each layer with a hand tamper or plate compactor. It’s important to achieve 95% compaction with backfill material.

The backfill should slope down away from the wall at an angle or grade of at least 1 inch per foot. This ensures gravity pulls water away from the wall and prevents saturation. You may need perforated drainage pipes behind the base of the wall if the soil has poor drainage. This carries away excess water. Backfill 2-3 feet behind the wall before grading the slope.

Check your grading with a level and fill any low spots as you work. Taking the time to properly install drainage and compacted backfill will give the wall strength and prevent problems like erosion, bulging or cracking down the road.

Building a Retaining Wall: Finishing Touches

The finishing touches give your retaining wall character and blend it into the landscape. Typical embellishments include decorative caps, copy, railings, and lighting.

Decorative Caps

Stone caps that extend past the edges of the wall blocks add visual interest. Caps protect the top course of blocks and hide any imperfections in alignment between courses. Standard rectangular coping stones work well. For a more decorative look, use corner caps or step caps on each course as it steps back.

Be sure caps are securely mortared in place and overhang the blocks below by at least an inch. Thicker caps of 3-4 inches are recommended for better durability and aesthetics. Match the look of your caps to the wall blocks, using the same or complementary materials.

Coping

Decorative masonry coping finishes off the top of the wall and provides an attractive transition between the wall and surrounding grades. Standard solid precast or masonry coping stones are widely available. For a softer look, use wall block coping made from matching or contrasting materials.

Install coping stones securely with mortar, leaving a slight slope so water runs off. Allow an overhang of 1-2 inches over the top course of wall blocks. Use thicker coping bricks if the wall will double as a bench or seating. Leave gaps between stones for drainage.

Railings

Safety railings will be necessary for taller, raised wall installations. Choose attractive, complementary metal railing styles. Black aluminum railings with simple lines blend well for a contemporary look. Or go for vintage appeal with powder-coated steel railings. Match the railing color and style to other outdoor accents and fixtures.

Connect railing posts securely to the retaining wall using appropriate hardware. Follow building codes for load capacity and spacing standards. Include a bottom rail for safety. On steep drops, use railings or fencing along the top of the wall as well as any stairs.

Lighting

Landscape lighting highlights the beauty of your retaining wall design and extends the enjoyment of the space into the evening. Hardscape lighting options include:

• Low-voltage lights recessed into the wall
• Lights shining up at the wall from the base
• Pole lights illuminating the wall
• Rail lighting on stairs or along top walls

For a polished look, run low-voltage wiring and fixtures through the hollow cores of wall blocks. Uplighting creates dramatic shadowing effects. Go for an even glow or spotlight certain focal points. Follow outdoor electrical codes for safety. Use LED bulbs for efficiency and long life. Automate lights to turn off at bedtime. Lighting transforms retaining walls from static structures into attractive design features.

Building a Retaining Wall: Maintenance

Proper maintenance is crucial for ensuring your retaining wall lasts for years to come. Here are some tips:

• Inspect your wall regularly, especially after major storms. Look for signs of bulging, cracking, or leaning. Address any issues right away before they get worse.
• Check for erosion around the wall, especially at the base and behind the wall. If soil is washing away, you may need to add backfill or install proper drainage.
• Clear debris, vegetation, and overgrown plants away from the wall regularly. Roots can cause cracks and damage.
• Reapply protective sealants per the manufacturer’s recommendations. Sealing the wall will prevent water damage and stains.
• Ensure proper grading and drainage around the wall to direct water away. Standing water can undermine the wall over time.
• Make any needed repairs with the original construction materials. Use the proper adhesives or mortars for a secure bond.
• Monitor for plant overgrowth on the wall. Trim back vegetation starting to creep onto the wall surface.

With consistent inspection and maintenance, a properly built retaining wall can remain sturdy and functional for decades. Addressing minor issues quickly preserves the wall and prevents more costly repairs down the road. Proper care protects your investment and retains the aesthetic appeal.

Conclusion

Building a retaining walls are a great way to create usable space in your yard, prevent erosion, and enhance the overall landscape. With proper planning and execution, you can build a strong, long-lasting retaining wall.

Planning to build a retaining wall?

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