A raised garden bed built with treated hardwood and Retain It posts, and coated with decking oil, with drainage installed.
I was looking to do some outdoor landscaping this summer break and planned to add a small raised garden bed/retaining wall to our back yard. Our yard is small to begin with and there is a decent slope that backs up to our back fence. The area wasnt really useable because of it and we wanted to box out the slope with a retaining wall to put ornamental plants.
The dimensions we wanted were 4.8m wide, 600mm high, and roughly 500-600mm deep from the back fence.
We purchased Bunnings 200 x 50mm 2.4m CCA treated hardwood and Retain It posts to construct the wall. We wanted something that would withstand the harsh, wet, and humid coastal weather of the Northern Rivers. We sealed the back and bottoms with two coats of Bondall black bitumen and the tops and faces we sealed with two coats of Cabots natural decking oil.
The garden bed wont be used for food. But with the level of sealing and backfill Im not too concerned with any CCA leaching into the soil or through the wood. We plan to reseal the surfaces every year or so. For anyone else interested in CCA research, I did find this interesting study showing that sealant on CCA wood is highly effective preventing leaching.
For anyone digging into super hard red earth clay, ditch the shovel and get a fencing bar. It would have been impossible without it.
Completing this small section was tricky as a 600mm concrete retaining wall with fence footing was already on the property line. And there was a 250mm gap between my sleeper garden bed/retaining wall and the concrete retaining wall. I ended up modifying a 450mm Retain It post to complete the section.
I used a 10mm cobalt drill bit to drill two holes in the Retain It post (didnt struggle getting through the post). The concrete sleeper already had two pre-drilled holes. Then I drilled two holes with a 10mm masonry drill bit into the concrete sleepers and secured the posts with two 75 x 10mm Dynabolts.
Our neighbours on both sides are higher than us and naturally water would travel to our property, and we didnt want it collecting behind the wall. I dug a trench around the perimeter directly behind the lowest sleeper. Then laid with gravel, then the Ag-pipe, and then filled with gravel. This backfill was around 200mm deep and enveloped in Geo fabric.
As we already have a stormwater drain in front of the retaining wall, I used 90mm PVC pipe to run the length from the drain to the wall, and a 100-90mm reducer to adapt to a T-joint at the stormwater pipe. And I used a Vinidex 100 x 90mm PVC Stormwater Draincoil Adaptor for attaching both Ag-pipes to the PVC.
We decided to replace the grass in front of the retaining wall with pavers as well. So it ended up being a long nine days of getting muddy.
I used two sheets of Geo fabric above tampered blue metal and below the pavers.
Filled the gap with 20mm gold aggregate and used H4 treated dividers with hardwood stakes for the paver boundaries and the ground level garden bed along the fenceline.
Were stoked with the results. Thanks for all the advice MitchellMc and the local crew at the Ballina Bunnings for the many tips along the way.
Raised garden beds bounded by retaining walls are an increasingly popular landscaping choice for their beauty and functionality. This eye-catching design allows you to cultivate plants in an elevated space while using the retaining wall to prevent soil erosion on slopes. With some planning, basic materials, and elbow grease, you can create a raised bed framed by a sturdy, handsome retaining wall.
Benefits of a Retaining Wall Raised Garden Bed
Combining a retaining wall with a raised garden bed offers numerous advantages
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Prevents soil runoff on slopes. The retaining wall holds back the hillside, keeping your garden bed’s soil securely in place.
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Creates extra gardening space. Building up behind the wall raises the planting level expanding your usable area.
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Improves drainage. Elevating the soil improves drainage while the retaining wall blocks water flow downhill.
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Enhances aesthetics. The structured look of a retaining wall lends eye-catching formality that showcases your garden.
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Increases planting flexibility. Retaining walls allow gardening on sites unsuitable for ground-level beds.
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Provides seating and borders. Retaining walls give you built-in options for seating, defining garden space, and edging paths.
With smart design and quality construction, a retaining wall raised bed marries beauty and functionality for an eye-catching garden focal point.
Choosing a Site for a Retaining Wall Raised Bed
The first step is picking the perfect spot. Consider the following factors:
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Sunlight. Most edible and ornamental plants need at least six hours of direct sun daily.
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Slope angle. A gentler slope is safer for construction. Steeper grades may require terracing or harder reinforcements.
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Soil stability. Loose or wet soil requires more reinforcement to prevent settling issues.
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Size. Make sure you have adequate space for your desired garden layout.
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Access. Easy access allows you to tend the garden and harvest crops conveniently.
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Views. Pick a high-visibility area to show off your handiwork.
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Existing features. Consider existing trees, structures, and utilities when choosing a location.
Take the time to carefully assess your options and select the ideal site before you start construction. This will ensure your raised bed and retaining wall last for years to come.
Building Retaining Walls for Raised Beds
Retaining walls for raised garden beds can be made from various standard landscape materials:
Concrete Block
Interlocking concrete blocks are a classic choice. Their uniform size and shape make them easy to work with. Opt for a high compressive strength concrete rated for retaining walls.
Pros:
- Affordable and readily available
- Easy to install
- Very durable
Cons:
- Can appear utilitarian
Natural Stone
For an organic look, use natural stone boulders or blocks. Local quarried stone offers style while blending with natural settings.
Pros:
- Provides custom, hand-built look
- Suitable for any environment
- Extremely durable
Cons:
- Higher cost
- Challenging DIY installation
Brick
Brick gives a classic, dignified look. Match existing masonry for a cohesive landscape theme. Use solid, weather-resistant bricks rated for retaining walls.
Pros:
- Familiar aesthetic
- Many styles available
- Relatively affordable
Cons:
- Not as durable as other options
- Mortar maintenance required
Timber
For a rustic feel, use dimensional lumber or timber panels. Naturally rot-resistant woods like cedar are best. Include ample reinforcement.
Pros:
- Affordable, accessible materials
- Easy to build
- Blends into natural settings
Cons:
- Shorter lifespan than other options
- Not ideal for steep slopes
Consider your design aesthetic, site conditions, budget, and DIY skill level when choosing retaining wall materials. Consult a landscape professional for recommendations specific to your property.
Constructing a Retaining Wall for a Raised Bed
Once you’ve chosen a spot and materials, it’s time to start construction. Follow these basic steps:
Step 1: Plan the Design
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Mark outlines for the wall, garden bed, and surrounding features.
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Determine the desired height and length for optimal space.
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Select materials and calculate needs based on project size.
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Sketch plans to visualize the finished look.
Step 2: Excavate and Level
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Remove enough soil to create a flat base for your wall to sit on.
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Dig a trench the width of your wall’s base and 6+ inches deep.
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Use a tamper to compact the soil, adding sand if needed to level.
Step 3: Build the Wall
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Lay the first course of blocks, checking alignment and level.
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Stack subsequent courses using the overlapping layout needed for your material.
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Follow specifications for installation of your specific retaining wall type.
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Include drainage materials like gravel backfill where required.
Step 4: Backfill and Finish
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Backfill behind the wall with additional soil layered and compacted.
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Shape the raised bed and ensure the soil inside is level.
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Cap the wall with specialty caps or topstones.
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Add final decorative touches like plants, lights, mulch, etc.
With proper planning and a methodical approach, you can DIY a raised bed with a beautiful matching retaining wall to elegantly solve your sloped yard challenges.
Best Plants for a Retaining Wall Raised Garden Bed
Once your retaining wall raised bed is prepped and filled, it’s time to decide what to plant! Consider these attractive, low-maintenance options ideal for raised bed gardens:
Edibles:
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Lettuce, spinach, kale, chard – Nutrient-packed salad greens thrive in raised beds.
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Carrots, radishes, beets – Root crops grow beautifully in the loose, amended soil of raised beds.
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Tomatoes, peppers, eggplant – Raised beds warm up quickly in spring for a long growing season.
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Herbs – Prolific basil, thyme, oregano, and more do well in raised beds and gardens.
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Strawberries – A retaining wall often creates ideal sloped conditions for sun-loving strawberries.
Ornamentals:
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Succulents – Low-care sedums, aloes, and agaves add texture.
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Ornamental grasses – Grasses like Muhlenbergia or Carex give movement.
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Echinacea, rudbeckia – Daisies, coneflowers, black-eyed Susans add cheerful color.
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Lavender – Fragrant, drought-tolerant lavender thrives in sunny raised beds.
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Viburnum, hydrangea, spirea – Flowering shrubs serve as small focal points.
Mix edibles and ornamentals together in your raised bed or plant separate beds for different functions. Take advantage of the excellent drainage provided by your elevated garden to grow a beautiful bounty of plants.
Reinforcing Retaining Walls on Steep Slopes
For particularly steep grades, additional reinforcement provides extra strength and stability for your retaining wall. Consider adding:
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Deadmen anchors: Buried concrete blocks tied to the retaining wall structure resist downhill forces.
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Geogrid: Horizontal layers of this polymeric reinforcing material distribute pressure along the wall.
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Post pilings: Steel or concrete pillars driven deep into the slope offer immense structural support.
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Concrete footings: A poured concrete footer rather than simple gravel backfill boosts the foundation.
Consult a qualified landscaping contractor to incorporate advanced reinforcement features for retaining walls on sharply sloped sites or high walls over 4 feet tall. Thoughtful design tailored to your specific property ensures your wall and raised bed will remain solid for decades.
Maintaining a Retaining Wall Raised Garden Bed
Like any landscape feature, some periodic care and maintenance helps preserve your investment in a retaining wall raised bed:
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Weed: Keep weeds from taking root in cracks or the raised bed itself. This prevents plants or roots compromising the structures.
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Erosion: Watch for any erosion issues behind the wall and refill soil as needed. Proper drainage prevents most erosion.
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Wall stability: Look for leaning, bulging, or sinking, which may indicate issues. Most quality walls need few repairs.
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Drainage: Ensure weep holes or drains stay clear to manage water flow and drainage behind the wall.
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Materials: Use weather and UV-resistant construction materials to limit deterioration or damage over time.
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Plants: Prune back vegetation to keep growth from overburdening the wall or raised bed.
With periodic checks and care, a properly built retaining wall raised garden bed will provide beauty, utility, and growing enjoyment for decades to come! Reap the rewards in terms of both increased planting space and enhanced curb appeal.
Transform Your Landscape with a Retaining Wall Raised Bed
With their elegant form and expanded planting capability, retaining wall raised garden beds are an increasingly
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Level Up Your Garden Bed with an Easy Retaining Wall
FAQ
What is the cheapest way to build a retaining wall?
1# The cheapest retaining wall type is the gabion basket wall. Gabion baskets are gravity designed and are built by filling galvanised wire baskets with stone. Gabion baskets are labour-intensive to construct. 2# The second cheapest retaining wall is the hollow block stepoc system.
What are the 7 common mistakes made when installing retaining wall blocks?
- Choosing the Wrong Material. …
- Not Providing Adequate Drainage. …
- Forgetting the Frost Line. …
- Too Much Weight Behind the Wall. …
- Inadequate Footing. …
- DIYing a Complicated Wall. …
- Not Maintaining Your Wall.
What is the cheapest retaining wall option?
Poured concrete is the cheapest type of retaining wall, in terms of materials. Pressure-treated pine is next, and wood retaining walls are becoming more popular now. If you prefer stone, granite is generally the least expensive option.
Should I line the walls of my raised bed?
Lining the bottom of your raised garden bed with a hardware cloth or wire mesh can be beneficial for preventing pests, like gophers and moles, from digging …
What is a raised garden bed?
A raised garden bed is a planting bed sitting above ground level. The bed typically comprises a garden area surrounded by a wood, stone, or brick frame that holds in the soil. Raised beds improve drainage and give you more control over soil quality, making gardening more accessible.
How do you design a raised bed?
Design your raised bed to blend into the contours of your yard like a natural feature. You can handle slopes in one of two ways. Either let your wall follow the slope of the yard for an informal look, or level the stones and step the wall up or down as the slope requires to maintain approximately the same height.
What are the benefits of a raised garden bed?
A raised garden bed offers many benefits over traditional in-ground gardening. Building your raised garden bed ideas using durable, attractive bricks allows you to quickly build a planting bed that will stand the test of time. Brick-raised garden beds don’t rot or leech chemicals, providing a safe option for growing edible plants.
Can I use wall block to create a raised circular bed?
Use wall block to create a raised circular bed and add an architectural element to your landscape. Product costs, availability and item numbers may vary online or by market. Wall block sizes vary by style and market. Use the quantity in the material list as a guide.
How do you build a rot-resistant raised bed?
Opt for naturally rot-resistant wood or use preservatives. Stone: Use large stones or using planter wall blocks for a decorative raised bed. Granite, limestone, and sandstone are good options. Or try a pebble mosaic design. Concrete blocks: These are cheaper than bricks. To strengthen, use reinforcement bars inside the blocks.
Can you build a raised bed on a slope?
Building a raised bed on a slope is tricky, but it can be done. Horticultural expert Lorin Nielsen discusses retaining walls, raised beds, and DIY builds for sloped gardens! Yards aren’t created equal. Some are beautifully flat and easy to work with, while others may be set on a sloped surface, either going up or down.