Landscaping with concrete blocks has become a go-to solution for outdoor design projects. From retaining walls and raised garden beds to patios, seating, and fire pits, concrete blocks offer strength, durability, and flexibility.
But despite their advantages, they are not foolproof. One wrong step—especially in planning or installation—can lead to expensive repairs or disappointing results. Whether you're a seasoned landscaper or a weekend DIY warrior, understanding the most common mistakes can save you both time and frustration.
Here are the five biggest mistakes to avoid when using concrete blocks in landscaping, along with expert tips on how to get it right from the ground up.
Mistake 1: Ignoring Drainage Requirements
One of the most damaging yet frequently overlooked errors in landscaping with concrete blocks is neglecting proper drainage—especially when constructing retaining walls.
Concrete blocks are strong, but they are not designed to hold back water. Without proper drainage, water can build up behind the wall, creating hydrostatic pressure that pushes the wall forward or causes it to bulge and crack.
If you skip proper drainage, your beautifully stacked wall could start leaning or collapsing within a season—particularly in wetter climates like New Zealand's.
How to Avoid It:
- Always include a gravel backfill behind the wall to allow water to drain freely.
- Lay a perforated drainage pipe (also known as a weeping tile) at the base of the wall.
- Incorporate weep holes at regular intervals to allow excess water to escape.
- Use geotextile fabric to separate soil from gravel and prevent clogging.
Failing to manage water is one of the quickest ways to ruin a retaining wall made with retaining wall blocks—so always plan for drainage before you start stacking.
Mistake 2: Skipping a Proper Base or Foundation
No matter how solid concrete blocks are, they're only as reliable as the foundation beneath them. Skipping or poorly preparing the base is a mistake that will come back to haunt you.
When blocks are laid directly on soil or uneven surfaces, they can shift over time, creating misalignment, cracking, or wall failure.
How to Avoid It:
- Excavate a trench below your intended wall or block line. The depth depends on the height of your project but typically should be at least 150mm.
- Fill the trench with well-compacted crushed rock or gravel. Compact it thoroughly using a hand tamper or plate compactor.
- Add a thin leveling layer of sand or fine gravel to ensure precision before placing your first course of blocks.
The first row of blocks needs to be perfectly level and aligned. Any errors in the base will only get worse as you build upward. A strong foundation is the backbone of any successful concrete block landscaping project.
Mistake 3: Choosing the Wrong Type of Concrete Block
Not all concrete blocks are suitable for every landscaping application. A common mistake is assuming that all blocks are interchangeable, which can compromise both the structural integrity and appearance of your project.
For example, using hollow cinder blocks for a load-bearing retaining wall is not only risky but could lead to dangerous collapses. Likewise, choosing smooth blocks for outdoor steps can create slipping hazards, especially in wet weather.
How to Avoid It:
- For retaining walls, use purpose-made retaining wall blocks that interlock or have built-in lips for added stability.
- For raised garden beds, lighter decorative blocks or even cinder blocks may suffice if they're not under pressure.
- For steps and stairs, choose blocks with a rough or textured surface to enhance grip.
- For fire pits, ensure your blocks are fire-rated or capable of withstanding high temperatures.
If in doubt, speak to your local landscaping supplier and describe your exact use case—they'll recommend the most suitable block type based on your project's demands.
Mistake 4: Overlooking Design Aesthetics
Concrete blocks may be utilitarian, but that doesn't mean your finished landscape has to look cold or industrial. A mistake often made—particularly in DIY projects—is neglecting the overall visual cohesion of the space.
Block-heavy installations can look harsh or out of place when they clash with surrounding architecture, materials, or garden elements.
How to Avoid It:
- Select block colours and textures that match or complement your home and other garden features.
- Break up hard edges by integrating soft landscaping elements, such as decorative bark, creeping plants, or grasses.
- Use white pebbles around block installations to lighten the appearance and contrast earthy tones.
- Consider curves, terracing, or multi-level design to create more visual interest than a flat, linear wall.
Don't underestimate the power of design in landscaping. Even small aesthetic decisions—like block finish or placement—can dramatically affect how inviting your garden space feels.
Mistake 5: Failing to Plan for Future Access or Modifications
When you're focused on completing a landscaping project, it's easy to overlook what might happen in five or ten years. But concrete blocks are semi-permanent. If you've locked in irrigation lines, buried lighting cables, or limited access to underground services, future maintenance can become a nightmare.
This is especially problematic in large or commercial landscaping where utility work is likely to occur.
How to Avoid It:
- Keep conduit pipes or sleeves beneath retaining walls or paths if future cabling might be needed.
- Leave inspection points or removable block caps for utility access.
- Plan landscaping layouts with expansion in mind—ensure you're not blocking future garden zones or planned structures.
- Avoid building directly over septic lids, irrigation controls, or underground utilities.
Planning for flexibility doesn't mean sacrificing your current vision—it means future-proofing it. You'll save yourself headaches down the road by anticipating how your landscape might evolve.
Real-World Example: The Cost of Cutting Corners
A homeowner in Auckland built a 1.5-metre retaining wall using standard concrete blocks on a sloped backyard. They didn't compact the base, skipped installing a drainage pipe, and stacked the blocks without staggered joints.
By the following winter, heavy rainfall caused soil to expand behind the wall. With no outlet for the water pressure and no reinforced base, the wall cracked in several places and partially collapsed.
In the end, the homeowner had to hire professionals to:
- Remove the failed structure
- Re-excavate the site
- Rebuild with appropriate retaining wall blocks
- Add gravel backfill, drainage pipes, and a compacted base
The redo cost more than double the original project—and could have been avoided with proper planning and materials.
Final Thoughts: Build Smarter with Concrete Blocks
Concrete blocks are one of the most dependable building materials in landscape design. When used correctly, they can help you create beautiful, functional, and long-lasting outdoor spaces. But they require thoughtful planning, correct installation, and an eye for both structure and aesthetics.
Let's recap the top five mistakes to avoid:
- Neglecting drainage behind walls
- Skipping a proper base or foundation
- Using the wrong block type for the job
- Ignoring aesthetics and overall design flow
- Failing to plan for maintenance or future modifications
Avoid these pitfalls and you'll be well on your way to a successful landscaping project that not only performs well but looks fantastic for years to come.
Whether you're starting a small DIY garden wall or a large-scale commercial landscaping job, explore high-quality materials like concrete blocks, retaining wall systems, decorative bark, and white pebbles from trusted suppliers.
Source : https://citilandscape.blogspot.com/2025/05/5-common-mistakes-to-avoid-when.html
