Concrete block retaining walls are a robust and reliable solution for sloped properties, terraced landscaping, and structural garden features. With the right planning, materials, and techniques, you can build a wall that stands the test of time — and looks good doing it.

Here’s your complete guide to building a long-lasting concrete block retaining wall, whether you’re taking the DIY route or managing a construction team.

Concrete masonry blocks offer:

• High compressive strength
• Versatile shapes and finishes
• Resistance to rot, termites and fire
• Compatibility with both mortar and dry-stack installation

Austral Masonry’s Concrete Block Range includes split-faced, honed, and smooth finishes to suit every project style.

From planning and preparing the base to the finishing touches, it is important to ensure structural integrity of any construction work. Here are the step-by-step instructions to build a sturdy concrete retaining wall:

Before digging, check:

• Council regulations: Most walls above 600mm need approval.
• Property boundaries: Ensure you're building within your lot.
• Drainage requirements: Retaining walls must allow water to escape to avoid pressure build-up.

Use string lines and stakes to mark out the wall length and height. Double-check slopes and site grading.

A strong wall starts with a strong foundation.

• Crushed rock (20mm)
• Road base
• Bedding sand

1. Excavate a trench 150mm deeper than your first course.
2. Fill the trench with 100mm of compacted road base.

3. Add a 10–20mm bedding sand layer and screed it level.

Compaction is key. Use a plate compactor to prevent future sinking or shifting.

• The first course is the most important. Take your time.
• Use a spirit level and mallet to adjust each block.
• Ensure blocks are tightly butted up against each other.
• Start at the lowest point and step up as needed to follow the slope.

Check level in both directions for every block. A mistake in this course will amplify in later rows.

• Dry stack: Easier for DIY, uses interlocking blocks and gravity.
• Mortar: Used with concrete blocks to offer a secure structure but requires skill to lay and curing time.

Offset the blocks in each row for better strength and appearance — this is known as a "running bond" pattern.

Required for walls over certain heights set in your building code, install vertical steel bars in filled cores. You can also add geogrid layers every two or three courses for added strength.

Lay a perforated agi-pipe behind the base course and slope it to daylight.

Use 20mm gravel behind the wall to a depth of at least 300mm.

Install behind the wall before backfilling to prevent soil from clogging your drainage layer.

Proper drainage is what separates a short-lived wall from one that lasts decades.

Cap blocks create a clean, professional look and protect from water ingress.

• Fix with masonry adhesive or mortar.
• Choose bevelled or flat-edge caps depending on your design.

Seal the wall if desired to protect colour and finish — especially for exposed or decorative face blocks.

1. Don’t skimp on compaction at any stage.
2. Always install proper drainage.
3. Avoid overloading the top of the wall with paving or heavy structures unless reinforced.
4. Use high-quality materials and follow the manufacturer’s recommendations.

Concrete block retaining walls are a smart, long-term investment for any outdoor project. With good design, solid foundations, and proper drainage, your wall can perform reliably for 50+ years.

Explore the Austral Masonry concrete block range to find structural and aesthetic options that suit your landscape needs.

Here are quick, informative answers on using concrete blocks for your next project:

Concrete block walls can last for up to 100 years with proper construction, drainage, and maintenance. Its durability makes them ideal for structural and landscaping applications.

Concrete blocks are prefabricated building materials made using a mixture of cement, aggregates, and water. This offers durability and convenience in the long run. On the other hand, cement is a binding material that is not suitable for standalone structural use.

The best adhesive for concrete blocks are those specifically designed for masonry. This includes a polyurethane-based or solvent-based formula. These adhesives provide strong bonding that are weather and moisture resistant, and are ideal for securing cap blocks or small repairs without using mortar.