Up to what height can I build a retaining wall?

We receive a lot of questions about what height retaining walls can be built up to. This blog examines how modular retaining walls, interlocking retaining walls, and concrete block retaining walls can meet all project retaining wall height requirements.

The height that a retaining wall can be built up to is dependent upon the type of retaining wall itself. 

There are four main types of retaining walls typically used for residential housing projects: 

The height restrictions arise due to the method used to construct the retaining wall and can be impacted by the nature of the ground conditions on site. 

Gravity retaining walls 

As the name suggests, the weight of materials used to build gravity retaining walls is used to hold back the pressure of the earth behind them. They do not need additional support to retain the soil.  The materials can include bricks, concrete blocks, and mass cast in-situ concrete. Factors such as the width of the base and slope of the face of the retaining walls affect the maximum height that can be reached. 

Reinforced retaining walls 

These are constructed in a similar way to gravity walls. However, they use different methods such as layers of geogrid and masonry reinforcement to support the soil behind the wall. This extra reinforcement allows the walls to be built much higher than a gravity wall. In the case of concrete block retaining walls, also referred to as modular retaining walls, using geogrid layers there is no restriction on their height.  

Cantilever retaining walls 

These are made of reinforced concrete and are usually ‘L’ or ‘T’ shaped. They are designed to transfer the vertical stress from the soil onto the base slab or footing. This enables the vertical section to support the weight and lateral forces of the retained soil, and they typically reach up to 5m in height. 

Embedded retaining walls 

These walls drive interlocking sheet piles or bored concrete piles down below the position of the retaining wall to use the passive earth pressure in the ground to retain the soil. They are usually chosen where poor soil conditions are unsuitable for other types of retaining wall. The height they can achieve is dependent upon those soil conditions and the wall type. If constructed using king posts the wall could be at a maximum of around 4m whereas walls that include extra reinforcement along with piling can get to a maximum height of 10m. 

For housing developments, reinforced retaining walls are a popular choice due to their flexibility in meeting height requirements and complementing project aesthetics. While brick reinforced retaining walls may be considered for their visual appearance, they lack the strength of alternative materials and require the skills of bricklayers in their construction.  

Modular retaining walls using interlocking concrete blocks can meet both the strength and aesthetic requirements for housing development projects and bring with them a host of other advantages. 

In addition to their unlimited height what other benefits do modular retaining walls bring? 

Modular retaining walls use interlocking concrete blocks and do not require mortar in their construction, offering a material cost reduction to the project.  

Whilst interlocking concrete retaining walls need to be built by suitably trained installers, their mortarless construction can be carried out without the additional skills of a bricklayer. The simplified design of concrete retaining wall blocks makes their installation an intuitive and smooth process that can offer significant project time savings for developers.  

The removal of mortar also makes the construction of interlocking retaining walls less weather dependent than when wet trades are required. This is worth considering because of the possibility of expediting build time on-site and reducing build costs. 

The concrete blocks used in modular retaining walls offer high strength when compared to standard bricks. When the height of a brick reinforced retaining wall increases, the base needs to widen accordingly to provide the required strength for the structure to support the soil behind it.  

Interlocking retaining walls that use geogrid for reinforcement offer excellent strength and can save project material and labour costs when compared to a masonry retaining wall of the same height. 

As well as offering cost and time savings, modular retaining walls are robust, durable solutions that are available in a range of styles and colours to provide developers and specifiers with a wide choice to complement their project’s aesthetic requirements. 

Where can I get more information on the heights and advantages of concrete block retaining walls? 

The exceptional stability of Secura Grand blocks by Tobermore helps specifiers construct concrete block retaining walls to meet a wide range of retaining wall height requirements.   

When Secura Grand blocks are reinforced with geogrid layers, they use granular aggregate fills in the hollow core of the blocks to lock them together and connect them to the geogrid. Under loads, the geogrid’s ribbed texture grips the coarse surface of each block, creating friction to help limit movement. A nib on each block resists forward movement and clamps geogrid layers in place. This three-way locking mechanism allows Secura Grand reinforced retaining walls to meet all project retaining wall height requirements. Secura Grand is BBA and HAPAS certified to the height of up to 9 metres, but construction may exceed the height as required. 

Tobermore has an in-house team that can provide you with preliminary design support packages for our Secura Retaining Walls. 

Created via our bespoke Secura design software, our complementary site-specific preliminary design service aids specification and planning to save time and money on-site. We have partnered with a network of geotechnical experts who specialise in retaining wall design and support from Tobermore even extends to checking that the most cost-effective backfill has been selected to keep a tight control on project costs. 

Alex Walther, Head of Retaining Walls at Tobermore, comments about the strength of the Secura Grand product and the support offered to customers:

“As well as offering a robust and exceptionally stable way to construct reinforced modular retaining walls with Secura Grand to any height required, our customers also benefit from the extra tools that we can offer to support them throughout the whole project. Through our experience and expertise, we help with the design, construction and timely delivery of cost-effective retaining wall solutions for our customers, and they love it.” 

If you would like to learn more about heights that can be achieved by concrete retaining wall blocks, you can book a CPD that can be carried out in person or remotely, or contact our sales team who will be happy to guide you through the retaining wall choices available for your project.