🖼️
The project:
Our old timber retaining wall was failing, so instead of simply replacing it, I increased the height and turned it into a raised garden bed. The new wall not only retains the soil but also creates a practical planting space along the fence. I finished it with composite cladding, a timber cap, tropical plants and decorative pebbles to give the area a modern, low-maintenance look. It completely transformed what was once a tired, unusable space into one of the standout features of our yard (and maybe the whole street?)
- Materials:
Treated pine sleepers (2.4 m × 200 mm × 75 mm)
Treated pine posts
Quick Set Post Concrete
Exterior-grade timber screws
Countersunk timber screws
Bitumen timber protector
Waterproof membrane
Agricultural drainage pipe (Ag pipe)
Drainage gravel
Geofabric / landscape fabric
Composite fluted cladding
Timber battens
Merbau timber capping
Watsons Water-Based Clear Timber Stain
Timber putty
Premium garden soil
Decorative pebbles
Plastic gravel grids
Landscape Lock pebble binder
Tropical plants (elephant ears, Cordyline, and other shade-tolerant varieties)
- Tools:
Tape measure
Paint brushes
Spirit level
Shovel and mattock
Gorilla garden cart
Circular saw or drop saw
Bosch Drill and impact driver
String line
- Step 1:
The fence line was originally covered by a large hedge that needed constant trimming and dropped leaves everywhere, making the area high maintenance. After removing the hedge and grinding out the stumps, I uncovered the original timber retaining wall, which had started to fail and was no longer supporting the soil properly. Rather than simply replacing it, I saw it as an opportunity to completely transform the space. I cleared the area, removed the old retaining wall and prepared the site to build a new, higher retaining wall that would double as a functional raised garden bed and create a much cleaner, more modern look.
We started by staining the original fence with Intergrain Natural Stain in Merbau.
- Step 2:
Planned the new retaining wall
With the old wall removed, I measured the full 10-metre fence line and used a string line to plan the finished height across the sloping block. After working out the levels, I chose 2.4 m × 200 mm × 75 mm treated pine sleepers and built the wall three sleepers high. This gave me enough height to accommodate the slope while keeping the top of the retaining wall perfectly straight and level. Planning everything first also helped me work out the post spacing, the number of sleepers needed and ensured the finished garden bed would look clean and consistent from end to end.
- Step 3:
Installed the new posts
Once the layout was marked out, I dug the post holes and positioned each post so it lined up with the centre of the 2.4 m sleepers, giving the wall plenty of strength and support. Before installing them, I coated each treated pine post with bitumen timber protector to help protect the timber below ground from moisture. Each post was then set in Quick Set Post Concrete and checked from every angle to make sure it was plumb, level and lined up perfectly with the string line. Taking the time to get the posts right made the rest of the build much easier and ensured the finished wall was straight and solid.
- Step 4:
Built the retaining wall
Before installing the sleepers, I coated each one with bitumen timber protector to provide extra protection against moisture and help extend the life of the timber. Starting from the bottom, I fixed the 2.4 m treated pine sleepers to the posts using exterior-grade timber screws, checking each course for level as I worked my way up. Building the wall three sleepers high allowed me to retain the sloping block while creating a strong, level raised garden bed. Once all the sleepers were secured, the new wall was solid, practical and ready for waterproofing and drainage.
- Step 5:
Waterproofed the wall and installed drainage
To help the retaining wall last for years to come, I installed a waterproof membrane along the back of the sleepers before backfilling. I then laid an agricultural drain behind the wall, surrounded it with drainage gravel and wrapped it in geofabric to help prevent blockages. The drain was connected into the existing drainage system, allowing excess water to flow away from behind the wall. This helps reduce pressure on the retaining wall and keeps the garden bed draining properly after heavy rain.
- Step 6:
Installed the cladding and timber capping
With the retaining wall complete, I gave it a more modern look by installing composite fluted cladding across the front. The cladding was fixed to the timber to create a clean appearance while hiding the structural retaining wall behind it. I then installed a Merbau timber capping along the top, which tied everything together and created a practical edge for the garden bed. This step completely changed the look of the wall, turning it from a basic retaining wall into a feature of the backyard.
- Step 7:
Finished the timber capping
To protect the timber while keeping its natural look, I applied two coats of Watsons Water-Based Clear Timber Stain to the Merbau capping. For a cleaner finish, every screw was countersunk so it sat below the surface of the timber. The screw holes were then filled with timber putty, allowed to dry, and sanded smooth until they blended in with the surrounding timber. This extra attention to detail gave the capping a seamless, professional-looking finish and really completed the overall project.
- Step 8:
Finished the garden bed
With the construction complete, I filled the raised garden bed with quality soil and planted a mix of low-maintenance tropical plants to create a lush, layered look. I chose plants with a range of colours, textures and heights to give the garden year-round interest while keeping it easy to maintain.
Around the front of the garden bed, I installed plastic gravel grids to help keep the decorative pebbles in place and create a more stable surface. The pebbles were then secured using Landscape Lock to stop them moving or spreading over time. These finishing touches gave the project a clean, modern look while making the area easier to maintain.
- Step 9:
After a final clean-up and some solar lights, the transformation was complete. What started as an old hedge and a failing retaining wall is now a modern raised garden bed that adds colour, structure and character to the backyard. The whole project was surprisingly straightforward and took around two weekends to complete. It not only solved the original retaining wall problem but also created a practical, low-maintenance feature that completely changed the look of the space. Seeing the finished result made all the effort worthwhile, and it's now one of my favourite DIY projects.
