Interlocking Concrete Blocks for Retaining Walls
Strong. Simple. Proven.
When it comes to designing retaining walls, engineers and contractors now have more choice than ever. From cantilever systems and king posts to modular gravity walls, few options are as quick and versatile as Allegro® interlocking concrete blocks.
Built for strength, designed for flexibility, and available for delivery across the UK, Allegro® blocks make retaining wall construction faster, cleaner, and more cost-effective.
Types of Retaining Wall
There are four main retaining wall systems typically used in construction. Each offers its own advantages depending on height, load, and site conditions.
Gravity Retaining Wall
Heavy, self-supporting structures built from interlocking concrete blocks such as Allegro®.
Cantilever Retaining Wall
Precast L-shaped units where a reinforced base provides stability.
King Post Retaining Wall
Steel columns with prestressed concrete panels slotted between.
Mechanically Stabilised Earth (MSE) Wall
Modular wall panels combined with geogrid or geotextile reinforcement.
Interlocking systems are often the best choice when speed, access, or flexibility for temporary works are priorities.
Design Factors to Consider
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- Location – Near water, motorways, or boundaries? Exposure and design life requirements will differ.
- Design Life – Allegro® blocks are cast from C40 concrete and are engineered for up to 100 years of service.
- Retained Height – Our interlocking blocks can form walls up to 5–6 m high when properly engineered and based on site conditions.
- Surcharge Loading – The system safely supports material densities up to 18 kN/m³ and surcharges up to 20 kN/m² from vehicles or stockpiled materials.
How Allegro® Interlocking Blocks Work
Each Allegro® block has a nib-and-recess design that locks units together both horizontally and vertically. No fixings or grout are needed – the wall’s stability comes from its mass and shape.
Blocks are placed directly on a reinforced concrete foundation, stacked in a running bond pattern, and can be backfilled immediately. The system can be dismantled and reused, making it suitable for both permanent and temporary retaining walls.
Since Allegro® blocks are unreinforced, there’s no steel to corrode, and maintenance requirements are minimal.
The Allegro® Range
We manufacture three core sizes to suit different wall heights, surcharges, and applications.
| Range | Typical Use | Dimensions (mm) | Weight | Max Surcharge | Key Benefits |
|---|---|---|---|---|---|
| 1.5m Allegro® | Low-level retaining walls, dividing bays, light storage | 1,500 × 600 × 600 | 1.1t | 20 kN/m² | Compact, easy to handle, quick to reposition for temporary works |
| 1.6m Allegro® | Heavy-duty storage bays, waste & recycling sites | 1,600 × 800 × 800 | 2.46t | 20 kN/m² | Wider, heavier profile for increased stability and higher walls |
| 1.8m Allegro® | Large-scale walls, fast installation, permanent retaining | 1,800 × 600 × 600 | 1.52t | 20 kN/m² | Longer blocks for fewer joints and faster construction |
The modular design allows you to combine block types to widen bases, form stepped profiles, or increase wall mass for higher surcharge capacity.
Benefits of Allegro® Interlocking Blocks
Speed of installation – up to 55 blocks (approximately 70m² of wall) can be installed in a day.
Immediate backfilling – no curing or delays.
Durability – factory-controlled C40 concrete, A1 fire rating, and freeze-thaw resistance.
Flexibility – corners, curves, and stepped walls can be built using half or angled blocks.
Sustainability – reusable and recyclable, reducing on-site waste.
Low maintenance – unreinforced design eliminates the risk of corrosion.
Typical applications
Allegro® interlocking concrete blocks are used across multiple sectors:
- Storage Bays – Aggregate, salt, grain, compost, and recycling.
- Retaining Walls – Embankments, cuttings, and landscape terracing.
- Temporary Works – Flood defences, vehicle barriers, and access protection.
- Industrial Compounds – Secure perimeters for plant and equipment.
Whatever the setting, Allegro® blocks offer a stable and flexible solution that can develop with your site.
Handling and Installation
- Supplied with cast-in lifting pins for safe handling.
- Installed using a telehandler, forklift, or 360° excavator.
- Delivered nationwide, with lead times typically between 2–4 weeks.
- Can be easily dismantled and relocated for future projects.
Build Smarter with Allegro®
Every Allegro® retaining wall system is designed for performance, practicality, and long-term value. Whether you’re constructing a small dividing bay or a multi-tier gravity wall, our blocks offer the flexibility to create stronger, quicker, and cleaner precast solutions.
Explore the full Allegro® Interlocking Block Range or view detailed specifications for our 1.5m, 1.6m, and 1.8m options to find the ideal fit for your next project.
