A retaining wall comparison – which one suits your project?

The most suitable retaining wall for your project will be one that delivers on both form and function. The form of a retaining wall includes the colour, texture, and shape of the materials, as well as how well they match the overall aesthetics of the project.  

 The functional performance required from each retaining wall on a site will depend on several factors. These include the type and volume of the soil to be retained and the resulting lateral soil pressure that the retaining wall must be designed to withstand. Where areas of retained soil are subject to additional loads, this surcharge must be added to the overall loading calculations. The presence of water in the soil will introduce additional hydrostatic soil pressure. Therefore, effective drainage strategies must also be included within the functional considerations for retaining walls. 

 As well as form and function, other considerations come into play when specifying a retaining wall solution, including its speed of build, ease of construction, quality of finish, and durability. We will have a look at some common types of retaining walls to see what they can offer your construction project and also consider in more detail retaining walls for housing projects. 

 What different types of retaining walls are typically used for housing projects? 

There are four main types of retaining walls typically used by projects: 

• Gravity retaining walls 

• Reinforced retaining walls 

• Cantilever retaining walls 

• Embedded walls 

Advice from the project’s structural engineer should always be sought to ensure suitable retaining wall solutions are proposed based on site soil conditions and loadings. We will cover all types of walls, but it is worth noting that gravity and reinforced retaining walls are most suitable for housing developments.  

 Gravity retaining walls 

Gravity retaining walls use their own weight and gravity to hold back the lateral pressure of the earth behind them. They can be constructed from a variety of materials including bricks, concrete blocks, and mass cast in-situ concrete and do not require additional support to retain the soil. They are often used for housing projects and hard landscaping. 

When building a gravity wall its maximum height will depend on its design – those with wider bases and sloped faces can reach around three metres before their combined weight and space requirements make alternative choices more attractive.  

Pros 

• Easy installation with no machinery needed 

• Available in many colours, textures and finishes to complement the aesthetics of a project  

Cons 

• Height limitations 

• Brick wall options require the skills of a bricklayer 

Reinforced retaining walls 

Reinforced retaining walls are built in a similar way to gravity walls. However, as the name suggests, they use different methods to reinforce the soil behind the wall. Methods include layers of geogrid and masonry reinforcement. The reinforcing materials support the ground behind the retaining wall and allow it to be built much higher than a gravity wall. This reinforcement enables the retaining wall to also support extra weight, or surcharge, in addition to that of the retained soil. These are ideal for hard landscaping of housing projects, as well as application for highways. 

Pros 

• Many finishes and styles available 

• Can be built up to an unlimited height 

• Concrete blocks such as Tobermore Secura Grand are interlocking and installers suitably trained in their use can construct retaining walls without the need for the additional skills of a bricklayer 

 Cons 

• Brick versions require skilled bricklayers 

• Can be slow to construct  

 Cantilever retaining walls 

Cantilever retaining walls are usually ‘L’ or ‘T’ shaped and are made of reinforced concrete. They work by transferring the vertical stress from the soil onto the base slab or footing. This allows the vertical section to support the weight and lateral forces of the retained soil. 

 Pros 

• Occupy relatively little space once constructed 

• Can be built up to five metres high 

 Cons 

• Need space behind the wall to allow its construction, so not suited to supporting existing slopes. 

• Requires large reinforced concrete foundation 

 Embedded walls 

Embedded retaining walls refer to those that use interlocking sheet piles or bored concrete piles to drive down below the excavation and take advantage of the passive earth pressure in the ground below. They tend to be needed where loose soil conditions are too poor for alternative types of retaining walls and priority is placed on their functional performance rather than visual appearance. It is possible to use embedded systems, such as King Posts, where panels fixed between the posts made of timber or textured and coloured concrete can add to the aesthetics of a project. These panels can be timber or made of plain, textured, or coloured concrete.  

 Pros 

• Useful where loose soils are present 

• Need limited space for installation 

 Cons 

• Heavy piling machinery required 

• Very limited finishes if visual appearance is important for a project 

• Generally a very expensive solution 

Which retaining wall options offer the most flexibility when considering the needs of housing projects? 

Of the options available, gravity walls and reinforced retaining walls offer the most flexibility for housing and hard landscaping projects. They offer the widest choice of appearance, style, colour and finishes, and have the functional performance characteristics to provide soil retainment for a wide variety of projects. 

When constructing these retaining walls, material choice can affect both the performance and visual appearance of the resulting construction. 

Where bricks have been used in the construction of surrounding houses or buildings, the temptation can be to also specify bricks for retaining structures for aesthetic reasons. However, bricks lack the strength of alternative materials. As the height of the retaining wall increases, the base of brick built retaining walls needs to widen to provide the required strength to support the soil. This increases both the material and labour costs when high retaining walls are needed. Bricks also need mortar for their construction adding material cost, and additional time, to projects and skilled bricklayers are needed for their construction.  

Gravity walls 

Secura Grand by Tobermore consists of heavier concrete retaining wall blocks and can be used as a gravity wall up to a maximum retained height of one metre. Retained height is measured from ground level to the underside of the coping and does not include the course of blocks required below ground. However, as we will see in the next section, when used with reinforcement materials, they offer a flexible solution. Secura Grand is the most popular choice for retaining walls higher than one metre or where the surcharge or ground conditions exceed the criteria for a gravity wall. 

 Reinforced retaining walls 

Secura Grand concrete retaining wall blocks can also be built using a simple, mortar-free dry method. By using concrete backfill with Secura Grand, retaining walls up to six metres can be achieved and where the geogrid method of reinforcement is used, walls can be built to an unlimited height.  

Secura blocks benefit from a three-way lock giving them exceptional structural stability from: 

1. Granular aggregate fill in the hollow core that locks blocks together and positively connects them to the geogrid 
2. Ribbed textured grips that provide friction locking between blocks and onto to geogrid layers 
3. Rear retaining nib that resists forward movement of the concrete block and clamps geogrid layers in place. 

 Secura Grand is used in residential projects to larger commercial developments and Secura Grand geogrid reinforced walls are BBA HAPAS approved for use in highways and bridges. 

 Alex Walther, Retaining Wall Category Manager at Tobermore, comments about the flexibility of Secura Grand:

“We find customers really appreciate the speed and efficiency that using Secura Grand segmental retaining wall blocks brings to their projects. The mortarless system reduces materials on-site and the process does not require bricklayers who are in high demand, and our system can be constructed in all weathers.”

Where can I get more information on the use and benefits of concrete retaining wall blocks? 

Tobermore has extensive expertise and experience in supplying our range of Secura Grand concrete retaining wall blocks to meet a wide range of project requirements. We have literature available for download and you can get access to full technical information and BIM models in a range of formats. 

Tobermore has an in-house team that can provide you with a free preliminary design support service. We have partnered with a network of geotechnical experts who specialise in retaining wall design and have vast experience in designing retaining walls throughout Europe. 

If you would like to learn more about the use of 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.