Building a retaining wall can seem like an intimidating project, but with the right planning and materials, it is quite achievable for a motivated DIYer. A retaining wall holds back soil and provides structural support in areas of uneven or steep terrain. Constructing one properly allows you to create usable space in your yard while preventing soil erosion.
We will walk through the entire process of how to build a retaining wall, from planning and design to preparing the base and selecting blocks. With smart preparation and diligent work, you can create a functional and beautiful retaining wall with a professional finish.
Design and Planning Your Retaining Wall
The first step to a successful DIY retaining wall project is proper planning and design. There are a few key factors to consider:
Choose Wall Location
- Look at your yard and determine the areas that could benefit from a retaining wall, such as:
- Steep slopes or hills that are eroding
- Creating usable flat spaces in uneven terrain
- Areas that need support due to changes in grade
- Consider sunlight exposure, drainage, proximity to utilities and views when choosing a location.
Determine Wall Height
- Measure the height of the slope or grade change the wall needs to retain.
- Retaining walls over 4 feet tall may require special engineering.
- The height will impact the wall’s design and base size requirements.
Check Building Codes and Permits
- Most areas require permits for retaining walls over 4 feet tall.
- Make sure to research and comply with local building codes for retaining walls.
Choose Wall Materials
- Common options include concrete blocks, stones, bricks, wood timbers.
- Consider factors like budget, aesthetics, longevity, and ease of construction.
- Heavier materials like concrete require a wider base but are easier to work with.
Plan for Drainage
- Proper drainage is critical to prevent buildup of hydrostatic pressure behind the wall.
- Incorporate drainage materials such as gravel, perforated pipe, and filtration fabric.
- Ensure water can flow away from the retaining wall and surrounding areas.
Design Wall Dimensions
- The wider the base, the more structural support. A good rule of thumb is 1/3 to 1/2 the wall height.
- Account for a footer extension or piling below ground level.
- Space any reinforcement such as geogrid according to manufacturer instructions.
Thorough planning and design will set your DIY retaining wall project up for long-term success. Consulting with an engineer is recommended for walls over 4 feet tall.
Preparing the Base Area
Once you have a plan in place, it’s time to start prepping the base area. Proper base preparation establishes stability and structural integrity for the life of the wall.
Mark Layout
- Use spray paint or stakes to mark the placement of the back of the wall.
- Mark the forward edge of the base.
- Verify the planned height aligns with the slope grade.
Excavate Soil
- Dig out the soil to the desired depth and width of the planned base.
- Excavate 6-12 inches below ground level for the footing or piling.
- Remove large rocks and smooth and compact the soil.
Add Gravel Base
- Cover the excavated area with 4-6 inches of compactible gravel.
- Compact the gravel thoroughly in 2 inch layers using a hand tamp or plate compactor.
Install Footing or Pilings
- For concrete block walls, install reinforced concrete footings per the engineered design.
- For interlocking block or natural stone, insert vertical pilings or pins.
Install Perforated Drain Pipe
- Lay perforated plastic drain pipe along the base, gently sloped to daylight.
- Wrap pipe in filtration fabric and cover with drainage gravel.
Taking time to establish a proper foundation will provide long-lasting stability and prevent shifting or erosion under the retaining wall.
Choosing Retaining Wall Blocks
There are a variety of material options when selecting retaining wall blocks. Consider the pros and cons of each to choose the right system for your project:
Poured Concrete
- Very strong and long lasting but requires building forms.
- Can be tinted or stamped for decorative finishes.
- Extremely heavy, usually requires equipment to install.
Concrete Masonry Units
- Readily available interlocking blocks are easy for DIY builds.
- Allow for reinforcement and drainage fill materials.
- Limitations on curvature and typically need surface finish.
Natural Stone
- Provides a beautiful, organic aesthetic.
- Needs skilled masonry work, difficult for novice DIYers.
- Stones shift and settle more than rigid blocks.
Timber
- Softer look, complements natural surroundings.
- Relatively affordable and accessible material.
- Higher maintenance required, less structural lifespan.
Reinforced Earth
- Uses geogrid instead of mortar for flexibility.
- Needs special design, higher cost than basic masonry.
- Best for tiered gravity retaining walls on steep slopes.
There are pros and cons to each material type. Choose retaining wall blocks that best fit your budget, design goals, and skill level.
Leveling and Installing the Base Course
Once your base is prepped, it’s time to lay the first course of blocks. Taking time to level the base properly will make the rest of the build smooth sailing:
Mark the Base Heights
- Use a string line and line level to mark the height of the base course along the length of the wall.
- This ensures your first layer of blocks sits level across the entire base.
Lay Out the Base Layer
- Place the first row of blocks end to end along the base.
- Use a 4′ level often to check for level and flatness as you go.
- Use shims or gravel as needed to stabilize any uneven spots.
Check Alignment Frequently
- Use a string line behind the blocks to check front-to-back alignment.
- Verify the back corners are square for straight side-to-side alignment.
- Make minor adjustments as you work to keep the rows aligned.
Backfill as You Build
- Backfill and compact behind each section as you install blocks.
- Compact drainage aggregate behind blocks in 6 inch layers.
- This prevents the stack from shifting once you add height.
Taking the time to correctly level and align the first course provides the crucial foundation for building up. Work methodically and check for level often.
Stacking and Reinforcing Retaining Wall Blocks
Once the base course is complete, the real construction begins! Here are some tips for properly stacking and reinforcing the successive courses:
Maintain Alignment and Bond
- Always aligneach new row directly above the row below it.
- Blocks should overlap the joints between blocks below. This is called bond.
- Offset vertical joints row to row for best stability.
Use Drainage Fill
- Fill behind blocks with free-draining gravel, not dirt.
- Only use compactible aggregate, no sand. Sand erodes over time.
- Leave a slight slope, don’t compact completely flat.
Install Reinforcement Geogrid
- Roll out geogrid reinforcement every 1-2 feet of height per manufacturer specs.
- Overlap geogrid sections at least 6 inches and keep pulls taut.
- The geogrid extends stability and prevents leaning.
Check Level and Alignment
- Use a level on top of each completed row to confirm level.
- Check the back-to-front alignment with a string line periodically.
- Make any necessary adjustments to keep walls plumb and courses level.
Stack courses carefully, and take frequent measurements to ensure your wall stays plumb and level. This will prevent costly mistakes down the road. Reinforcement is key for walls above 3 feet tall.
Finishing Touches for a Professional Look
You’re nearing the top – don’t neglect the final details and touches that can take your retaining wall from DIY to pro-grade:
Install Capstones
- Glue capstones in place at the top of the wall using landscape adhesive.
- Choose wide capstones to span the full width of the blocks beneath.
- Caps should overhang the front and back of the blocks slightly.
Backfill Completely
- Fill behind the wall fully with drainage aggregate.
- Use the compacting method for each 6 inch layer.
- Slope excess fill away from the wall at the top.
Hide Exposed Cut Edges
- For sidecuts, backfill fully and install topsoil to hide block edges.
- On steep slopes, terracing can help avoid an exposed side wall.
Direct Water Away from Wall
- Ensure sprinklers, downspouts and runoff are directed away from the wall.
- Add swales above the wall if needed to divert water from it.
Take time for detail work at the top and edges for a wall that looks like a seamless part of the landscape. Proper finish work protects your investment and creates lasting curb appeal.
Troubleshooting Common Retaining Wall Problems
Even with proper planning and construction methods, issues can occasionally arise with retaining walls. Here are some common problems and troubleshooting tips:
Leaning or Bulging
Causes: Insufficient base, improper installation, lack of reinforcement, water pressure
Fixes: Add reinforcement geogrid, widen base, improve drainage
Cracking or Crumbling Blocks
Causes: Normal freeze-thaw cycles, inadequate curing of concrete, soil settling
Fixes: Patch cracks with epoxy, replace damaged blocks
Erosion and Washouts
Causes: Improper drainage, directing water towards wall, lack of plants
Fixes: Improve drainage, add plants to retain soil, divert water away
Sloped or Settled Wall
Causes: Unstable soil, uncompacted backfill, under-designed base
Fixes: Remove and rebuild on improved base, use geogrid reinforcement
Identify the cause of any issues to select the appropriate remedy. Preventative measures taken during design and construction are key to avoiding problems.
FAQs About Building Retaining Walls
Here are answers to some of the most frequently asked questions about retaining wall projects:
How deep should the gravel base be for a retaining wall?
For most smaller DIY walls, a base of 4-6 inches of compacted gravel is sufficient. Larger walls may require a deeper layer of aggregate base, around 12 inches or more.
What size blocks are best for building a retaining wall?
Standard sizes for retaining wall blocks are 4-6 inches high by 10-12 inches deep. Larger blocks become very heavy and harder for DIY installation. Smaller blocks require more time and precision to install.
How far apart should I space vertical joints in a block wall?
Vertically overlapping each new course over the joints in the row below provides the best stability. Space the blocks close together, with joints no wider than 1/4 – 1/2 inch.
Should drainage pipes be installed behind a retaining wall?
Yes, adding perforated plastic drainage pipes at the base allows water to flow freely away from the soil behind the wall. This drainage is extremely important for reducing pressure.
What is the maximum height I can build a DIY retaining wall?
It is recommended to limit DIY retaining walls to 4 feet tall without engineering. Going above 4 feet requires advanced design and permits in most areas due to the grade change.
How do I prevent erosion around the edges of my retaining wall?
Proper backfilling and compacting coupled with topsoil, plants and mulch around the edges helps reduce splash erosion around a wall. Directing water flow away from the wall also prevents edge erosion.
Thorough planning, diligent installation, quality materials and proper maintenance will yield a retaining wall that stands the test of time and enhances your landscape. Keep the tips and techniques covered here in mind throughout your build, and enjoy the satisfaction of creating a stable, attractive wall with your own hands.
Conclusion
Constructing a retaining wall is an ambitious project, but breaking it down into accessible steps makes it a very achievable DIY undertaking. Following proper design, preparing a stable base, selecting quality materials, reinforcing the structure, and applying finishing details allows you to reap the benefits of usable yard space, prevented erosion, and enhanced curb appeal. While specialized engineering and equipment is needed for massive retaining walls, backyard DIY walls up to 4 feet tall can be built by any motivated homeowner with good planning and persistence. Remember to check your local building codes, secure permits if required, and don’t be afraid to call in extra help for the heavy lifting. Your new retaining wall will provide both aesthetic and functional value for years to come.