Did You Know There Are Two Ways to Build Walls Over 15 Feet Tall with London Boulder BIG Blocks? – Precast Concrete Gravity Walls

When designing a precast concrete retaining wall, most people assume you must use geogrid reinforcement for anything taller than 10 feet. But that’s not the case.
With London Boulder’s precast modular block system, there are two proven engineered solutions to safely and efficiently build walls over 15 feet tall:

Use LB 28 blocks with geogrid reinforcement to create a reinforced wall design.
Or use larger blocks like LB 42, LB 52, or LB 60 to build a gravity retaining wall that relies purely on mass and block-to-block connection, no reinforcement required.

This flexibility gives contractors and engineers more retaining wall options and allows wall designers to choose the most cost-effective and space-saving design for their specific project.

Option 1: Reinforced Walls with LB 28 Precast Concrete Blocks

Example: The Cherrywood Point–Minnetonka project features a 15-foot-tall wall built entirely with LB28 blocks using geogrid reinforcement.

What It Is

In this design, you use smaller or mid-size precast concrete retaining wall blocks and reinforce them with geogrid.
The geogrid layers extend into compacted soil behind the wall, creating a composite structure that distributes pressure and increases stability.

Because London Boulder blocks are a fully engineered block system, they’ve been tested with multiple geogrid manufacturers and can be adapted to any job site—urban, commercial, or landscape applications.

Why It Works

The unique locking system between blocks ensures secure alignment and stability.

Geogrid reinforcement ties the facing units to the backfill mass, reducing overturning forces.

The modular design of these precast retaining wall units allows for quick, repeatable on-site installation.

When to Choose It

When space is not limited, and you have a fill wall situation.

When you’re dealing with sloping terrain or additional loads near the top of the wall.

When the project requires an engineered reinforced wall solution with professional oversight from contractors and engineers.

Practical Notes

Always ensure proper drainage and compaction of the reinforced soil zone.

Have your designer or licensed engineer verify grid lengths and layers.

Use free-draining granular fill to prevent water buildup and increase long-term wall performance.

Option 2: Gravity Retaining Walls with LB 42, LB 52 & LB 60

Example: Fernbrook Fields – Maple Grove: A 12.5-foot-tall wall constructed with LB60 blocks and smaller units, designed without any geogrid reinforcement.

What It Is

The second method uses larger precast concrete retaining wall blocks as a gravity retaining system—meaning the wall’s own mass and connection resists the pressure of the retained soil.
Instead of relying on reinforcement, these precast modular units create stability through their size, weight, geometry and block-to-block connection.

For example, the LB 60 block is 60 inches deep and weighs over 3,000 lbs. Its massive footprint allows you to build walls up to 16.5 feet tall without geogrid—an ideal choice for projects such as highway embankments, municipal infrastructure, and large-scale commercial landscape developments.

Why It Works

The block system uses interlocking lugs and multiple setback options to assist the design in resisting sliding and overturning.

The significant mass of each unit creates natural gravity, retaining strength.

The rugged, rock-like finish provides the appearance of natural stone while being durable precast concrete retaining construction.

When to Choose It

When there’s “no” room for excavation behind the wall.

When working on linear projects, such as highway retaining walls or large-scale infrastructure installations. As well as commercial applications with minimal space behind the wall.

When you want a straightforward build that’s easy to install, it reduces field labor and saves both time and money.

Field Advantages

Fewer components and faster construction cycles.

Minimal backfill materials—no need for geogrid or extended reinforced zones.

Consistent factory-controlled quality from precast concrete retaining wall blocks, ensuring reliability across large projects.

Example: Hamm’s Brewery – St. Paul: A 19.5-foot-tall wall built using LB72 blocks and smaller units, engineered to stand without geogrid reinforcement.

Comparing the Two Approaches

Feature	Geogrid-Reinforced LB 28 System	Gravity LB 42 / LB 60 System
Reinforcement	Uses geogrid reinforcement	None—gravity retaining
Maximum Height	15 ft + (depending on design)	Up to 16.5 ft (or even taller with longer units)
Base Width	Smaller footprint	Wider base
Excavation	More	Less
Installation	More steps	Simpler, easy to install
Equipment	Lighter blocks	Heavier lifting gear
Ideal Use	Open landscape or infrastructure projects	Tight urban or structural sites

Both approaches are fully engineered solutions from London Boulder, ensuring your designer and contractor can adapt them to virtually any terrain or slope.

The Value of Flexibility

1. Optimized Design Freedom

Because London Boulder offers both reinforced and gravity retaining wall configurations, wall designers can evaluate site conditions—such as loading, drainage, and available space—to select the right retaining wall units for each application.

2. Simplified Construction

A gravity retaining wall simplifies installation by eliminating the need for reinforcement layers and offers greater flexibility in tight spaces. Both reduce waste, cut rework, and save time and money.

3. Engineered Consistency

Every London Boulder wall is a fully engineered solution. The precision-cast precast concrete retaining units interlock seamlessly, offering consistent performance and a clean, professional finish.

4. Aesthetic and Functional Versatility

London Boulder has five different face styles to choose from. From landscape terraces to municipal roadways, London Boulder’s precast concrete retaining wall blocks combine strength and design appeal. Their natural stone-like appearance and durable surface texture make them ideal for both visual impact and long-term stability.

5. Real-World Proven Performance

These systems are used across the country in highway, commercial, and residential landscape projects. They deliver structural reliability while maximizing usable space above and below the wall—whether for parking lots, yards, or roadways.

How It Works: From Design to Installation

London Boulder’s precast modular block products are made to precise specifications, ensuring ease of placement and long-term durability.

Wall designers typically begin by analyzing:

Slope and soil type behind the wall.

Available usable space for the base or reinforcement zone.

Desired elevation change and aesthetic goals.

Once the plan is finalized, contractors and engineers coordinate equipment, delivery, and on-site installation. The blocks are set with standard lifting hooks, aligned using the unique locking system, and stacked to the design height. Because these precast retaining units arrive ready to install, crews can move quickly and minimize delays from weather or field variability.

Where These Walls Shine

Highway and Infrastructure: Long, continuous runs of precast modular blocks provide safe, strong retaining structures for overpasses and interchanges.

Commercial & Residential Landscape: Create multi-level terraces, garden walls, or property boundaries that add both structure and beauty.Slope Stabilization: Use either a reinforced wall or a gravity-retaining wall to convert steep grades into usable, functional space.

Whether it’s a city retaining wall or a backyard redesign, these precast concrete retaining wall blocks perform in every application—from heavy-duty infrastructure to decorative landscape settings.

Key Takeaways

Two Engineered Solutions: Build walls over 15 feet tall using either geogrid-reinforced or gravity retaining designs.

Precast Concrete Durability: Factory-made retaining wall units ensure precision, strength, and consistency.

Easy to Install: Modular components reduce on-site errors and speed up construction.

Saves Time and Money: The simplicity of the block system minimizes labor while maintaining structural reliability.

Proven Performance: From highway corridors to landscape developments, these precast modular block walls deliver trusted, long-term results.

Ready to Get Started?

If you’re a designer, engineer, or contractor exploring tall wall designs, London Boulder offers the expertise and versatility you need. Discover how our precast concrete retaining wall blocks can help you reclaim usable space, streamline construction, and enhance your next project.