How to lay retaining wall blocks on a concrete footing
This guide provides a comprehensive, step-by-step process for constructing a retaining wall using modular concrete blocks on a solid concrete footing. This method is ideal for creating level garden beds, terracing sloped backyards, or defining landscape features, ensuring stability and longevity for
- Skill level
- Intermediate
- Time
- 2-5 days (depending on wall length and height)
- Trade
- Building & Construction
- Updated
- 4 November 2026
Tools you will need
- Shovel
- Pickaxe
- Wheelbarrow
- Spirit level
- Rubber mallet
- String line and line level
- Tape measure
- Angle grinder with diamond blade
- Trowel
- Concrete mixer
🧱 Laying Retaining Wall Blocks on a Concrete Footing
What is involved in laying retaining wall blocks on a concrete footing?
This guide provides a comprehensive, step-by-step process for constructing a retaining wall using modular concrete blocks on a solid concrete footing. This method is ideal for creating level garden beds, terracing sloped backyards, or defining landscape features, ensuring stability and longevity for your project.
What skill level is required for laying retaining wall blocks on a concrete footing?
Intermediate — Estimated time: 2-5 days (depending on wall length and height)
What tools are essential for laying retaining wall blocks on a concrete footing?
Shovel (square mouth and round point) Pickaxe (for hard ground) Wheelbarrow Spirit level (1200mm and 600mm) Rubber mallet String line and line level Tape measure (8m) Angle grinder with diamond blade (for cutting blocks) Trowel (pointing and brick trowel) Concrete mixer (or wheelbarrow for small batches) Compactor/Wacker plate (for base preparation) Stiff broom Bucket Safety glasses Gloves Ear protection Dust mask (P2) Safety bootsWhat materials are needed for a retaining wall with a concrete footing?
Retaining wall blocks (calculate quantity based on wall length and height, plus 5-10% for cuts/breakages) Concrete mix (pre-mixed bags or cement, sand, aggregate for 1:2:3 general purpose concrete for footing) Reinforcing bar (N12 or N16) if specified by engineer Road base/Crusher dust (for bedding layer) Drainage aggregate (e.g., 20mm crushed rock, scoria) Geotextile fabric (non-woven, permeable) Agricultural pipe (slotted, 100mm diameter) Concrete adhesive/construction adhesive (e.g., SikaBond, Liquid Nails Landscape) Water Timber formwork (for concrete footing, if required) Pegs and stringWhat are the key safety requirements for retaining wall construction in Australia?
⚠️ Safety
PPE: Always wear safety glasses, gloves, ear protection, dust mask (P2), and safety boots. Manual Handling: Use proper lifting techniques when handling blocks, concrete bags, and heavy tools. Bend knees, keep back straight, and lift with legs. Get assistance for heavy items. Excavation: Be aware of underground services (dial 1100 before you dig). Ensure trenches are stable and not prone to collapse. Power Tools: Use angle grinder with extreme caution. Ensure guards are in place. Disconnect power when changing blades. Scaffolding: For walls exceeding 1.2m in height, consider scaffolding or a stable work platform to avoid working from ladders. Engineering: For walls over 1m high, or those supporting significant loads (e.g., driveways, structures), an engineer's design and certification are mandatory as per AS 3700 Masonry Structures and local council requirements.Step-by-Step Guide
Step 1: 1️⃣ Site Preparation and Excavation
Begin by clearly marking out the retaining wall's footprint using pegs and a string line. Ensure the line is level. Excavate a trench for the concrete footing. The trench width should be at least 150mm wider than your retaining wall blocks, and the depth should be sufficient to accommodate the footing (typically 150-200mm deep) plus any required embedment for the first course of blocks. Ensure the base of the trench is firm and level. For walls over 1m high, consult an engineer for footing dimensions and reinforcement.
Step 2: 2️⃣ Formwork and Concrete Footing
If your trench edges are not perfectly stable, install timber formwork to create a neat, level footing. Ensure the top of the formwork is level using a spirit level. Mix your concrete to a 1:2:3 general purpose ratio (1 part cement, 2 parts sand, 3 parts aggregate) or use pre-mixed bags according to manufacturer instructions. Pour the concrete into the trench, ensuring it fills all voids. Use a screed board to level the concrete with the top of the formwork. For structural footings, place reinforcing bar (e.g., N12 or N16) as per engineering specifications, ensuring adequate concrete cover. Allow the concrete to cure for at least 24-48 hours before proceeding, or longer in cooler conditions. Refer to AS 3600 Concrete Structures for curing guidelines.
Step 3: 3️⃣ Laying the First Course of Blocks
Once the concrete footing has cured, lay a 10-20mm thick bed of road base or crusher dust on top of the footing. This bedding layer helps to level the first course of blocks. Start laying your first course of retaining wall blocks, ensuring they are perfectly level both longitudinally and transversely using your spirit level. Use a rubber mallet to gently tap blocks into position. Apply concrete adhesive to the base of each block as you lay them, ensuring a strong bond to the footing. Maintain consistent alignment along your string line. This first course is critical for the stability and appearance of the entire wall.
Step 4: 4️⃣ Installing Drainage and Backfill
As you lay subsequent courses, it's crucial to incorporate proper drainage. Behind the first course of blocks, lay a layer of geotextile fabric against the excavated earth. Place a 100mm slotted agricultural pipe (ag-pipe) along the base of the wall, ensuring it slopes towards an outlet point. Cover the ag-pipe with at least 300mm of drainage aggregate (e.g., 20mm crushed rock or scoria). The geotextile fabric should wrap around the drainage aggregate to prevent soil migration into the drainage layer. This system prevents hydrostatic pressure buildup behind the wall, which can lead to failure.
Step 5: 5️⃣ Laying Subsequent Courses and Adhesion
Continue laying subsequent courses of blocks, staggering the joints (stretcher bond) for strength and appearance. Apply a generous bead of concrete adhesive between each course of blocks. Ensure each block is level and aligned with the course below. Use an angle grinder with a diamond blade for any necessary cuts to fit blocks at ends or corners. Always wear appropriate PPE when cutting. Periodically check the wall for plumb (vertical straightness) using your spirit level.
Step 6: 6️⃣ Compacting Backfill and Finishing
As you build up the wall, backfill behind the drainage layer with compacted soil or road base in 150-200mm layers. Compact each layer thoroughly with a compactor or hand tamper. This prevents future settlement behind the wall. Once the wall reaches the desired height, install any capping blocks if applicable, securing them with concrete adhesive. Ensure the top of the wall is level and neat.
Common Mistakes to Avoid
Pro Tips
💡 Dry Lay First: For complex layouts or corners, dry lay a few courses without adhesive to plan your cuts and ensure a good fit before committing. 💡 String Line for Accuracy: Always use a string line pulled taut and level for every course to maintain straightness and alignment. 💡 Waterproofing Behind: For critical applications or where moisture is a concern, consider applying a waterproof membrane to the back of the blocks before backfilling to further protect the wall. Refer to AS 3740 for waterproofing guidelines. 💡 Slope for Drainage: Ensure the ground in front of the retaining wall slopes away slightly to prevent water pooling at the base. 💡 Equipment Hire: For larger projects, hiring a concrete mixer and a plate compactor is far more economical than purchasing, and ensures you have the right tools for the job.Recommended Tools
🔧 Husqvarna K 770 Power Cutter: Excellent for precise and efficient cutting of concrete blocks. 🔧 Makita DHP481Z Cordless Hammer Driver Drill: Versatile for any drilling needs, especially for securing formwork. 🔧 Stanley FatMax Xtreme Level (1200mm): Essential for ensuring perfect level and plumb throughout the build. 🔧 Belle Minimix 150 Concrete Mixer: Ideal for mixing concrete batches efficiently for footings and bedding.Frequently asked questions
- What is involved in lay retaining wall blocks on a concrete footing?
- This guide provides a comprehensive, step-by-step process for constructing a retaining wall using modular concrete blocks on a solid concrete footing. This method is ideal for creating level garden beds, terracing sloped backyards, or defining landscape features, ensuring stability and longevity for
- What skill level do I need for lay retaining wall blocks on a concrete footing?
- Intermediate — Estimated time: 2-5 days (depending on wall length and height)
- What are common mistakes when lay retaining wall blocks on a concrete footing?
- 1. Insufficient Footing: A weak or undersized footing is the most common cause of retaining wall failure. Always ensure the footing is adequately sized and reinforced if required. 2. Poor Drainage: Failing to install proper drainage (ag-pipe and aggregate) will lead to hydrostatic pressure buildup, causing the wall to bulge or collapse. 3. Not Leveling First Course: If the first cou
- What tools do I need for lay retaining wall blocks on a concrete footing?
- This guide includes a comprehensive tools list. Key building & construction tools are detailed in the Tools Required section.
- What is the Australian standard for retaining wall construction?
- While there isn't one single Australian standard solely for retaining walls, AS 3700:2018 Masonry structures and AS 2870:2011 Residential slabs and footings are highly relevant. Local council regulations, based on the National Construction Code (NCC), also dictate requirements, especially for walls exceeding 1 metre in height or those near boundaries.
- How deep should a concrete footing be for a retaining wall in Australia?
- The depth of a concrete footing for a retaining wall in Australia depends on the wall's height, soil conditions, and any engineering specifications. As a general guide, the footing should extend below the frost line (if applicable) and be at least 150mm wider than the block course on each side, with a minimum depth of 200mm for walls up to 1 metre high, according to typical engineering practice.
- Do I need council approval for a retaining wall in Australia?
- Yes, in most Australian states and territories, council approval is required for retaining walls over 1 metre in height, or if they are located on or near a boundary, or if they support a surcharge (e.g., a driveway or building). Always check with your local council's planning department before commencing work.
Written by Bricko, the Building & Construction specialist at Aus.Tools.