How Important Are Retaining Walls?

A retaining wall is far from just a decorative element; it’s an essential for both structural and aesthetic reasons.

Used in all types of construction, from residential to commercial, as well as sea and river defence, retaining walls play a pivotal role in many different projects.

Read on as we explore the basics of retaining walls, why they are important, and all you need to know when it comes to tackling a project that requires a retaining wall.

What Is A Retaining Wall?

A retaining wall is a structure designed to hold soil back. Commonly used to prevent soil erosion, these walls counteract the force of the soil and improve its load-bearing capacity. With a retaining wall, the retained soil can take on the loads of buildings or traffic, which would otherwise be impossible without the construction of the wall.

A key factor in designing a retaining wall is drainage. The wall must be constructed with the right amount of drainage in order to prevent water from building up behind it. Failure to do so can result in a build-up of hydrostatic pressure, which leads to wall failure. Proper drainage will also prevent erosion and other damage to the soil behind the wall.

What Types of Retaining Walls Are Used in Housing Development?

Various types of retaining walls are used in housing development; however, the most common include:

Gravity

Gravity retaining walls rely on a large mass to resist the pressure from the material load. These walls are commonly constructed using materials such as poured concrete, stone or masonry. They will not require reinforcement or anchors and are ideal for shorter walls.

Cantilever

A cantilever retaining wall is one of the most common retaining wall designs in the UK. Typically made from reinforced concrete, they rely on leverage for stability. Consisting of an L-shaped or T-shaped base slab and a vertical stem, the two sections work together to convert horizontal soil pressure into vertical downward pressure.

These walls use fewer materials than a typical gravity wall, and are a popular choice for large-scale projects; that’s their strength.

Sheet Pile Walls

Sheet pile walls consist of interlocking steel or concrete sheets, driven into the ground to provide support. This type of retaining wall is typically found in underground structures such as basements, car parks, river embankments and sea walls. These walls are strong, durable and can be permanent and temporary, depending on the project’s requirements.

When Is A Retaining Wall Needed?

Steep Slopes

Properties with steep gradients will be more likely to face soil erosion, especially during periods of heavy rain. With a retaining wall, the slope can be stabilised, providing a barrier against soil displacement.

Water Accumulation

If you notice water starting to pool around the area, this could be a sign of drainage issues. Retaining walls help to manage water runoff by redirecting it away from buildings and other structures.

Creating A Level Area

Retaining walls are an excellent way to create a flat, level area for the construction of a patio, garden bed or driveway. For example, if you have a sloping driveway, a retaining wall can be used to reduce the gradient and make it easier and safer to park on.

Why Are Retaining Walls So Important?

Prevent Erosion & Soil Collapse

Soil collapse can lead to catastrophic damage to a property. Therefore, a retaining wall that is built properly and calculated to withstand load and pressure is vital. For example, in the construction of a basement, once the site has been excavated, the retaining walls will hold a huge amount of pressure exerted by the surrounding soil over a long period of time.

Maximise On Usable Space

Retaining walls make a sloped space functional. The walls flatten the slope and push the soil back, creating a flat terrace. This terrace can then be used for building a patio, garden bed or even a driveway.

Provide Stability and Safety

A retaining wall allows for greater structural stability, particularly in areas with challenging terrain or large-scale projects such as roadway overpasses.

Aesthetic Appeal

With a well-designed retaining wall, you can also enhance the beauty of your home, adding a modern touch, especially when you add lighting and other visual aspects.

How Are Retaining Walls Built?

Performing Soil Tests

Soil tests are required in order to assess the soil’s bearing capacity, to ensure that it can safely support the weight of the wall. With the soil’s composition, you can determine the type of retaining wall that is required.

Determine The Wall’s Function

First, you need to determine the wall’s function and calculate the applied loads that it will be required to hold. From this point, an engineer will be able to design the wall and determine the materials needed to build it.

Clear The Area

The chosen area for the wall must be cleared of vegetation, rocks and debris, all of which could negatively affect the stability of the retaining wall.

Excavation

Once the area is prepared, the excavation can start. This excavation will be a crucial part of the build, and is often the most challenging stage. This is often where it is helpful to employ the help of a groundworks specialist, who’ll have the right equipment and experience to quickly and efficiently carry out the excavation. A professional will also consider factors such as the groundwater levels, soil type, and proximity to existing structures. They’ll also be able to remove or relocate existing drainage channels, utilities and other infrastructures.

Building The Wall’s Foundations

Once the excavation is done, the foundations can be built. Typically made of reinforced concrete, the thickness and the depth of the foundation will be calculated based on the weight that will be supported and the soil composition.

Constructing The Wall

With the foundation in place, it is now time to construct the wall.

As the wall is built, drainage must be managed through weep holes, which release accumulated water and prevent it from building up behind the wall.

During this process, other drainage systems such as V-Ditches and French Drains are installed to ensure further water diversion.

Upon completion, the backfilling process will begin. This consists of installing a layer of geotextile fabric to further prevent soil erosion, and then compacting it with granular soil behind the wall.

Can I Build A Retaining Wall Myself?

Building a retaining wall is a specialist skill. It requires careful positioning and placement of each block, and the wall must be designed to suit the structural requirements.

If you are planning to build a retaining wall over 1 metre in height, it is vital that you get in touch with an expert, ideally a structural engineer or a specialist in retaining walls.

In any construction project, never compromise on your foundation, including your retaining walls. When you can change most aspects of your home, the foundation is permanent, and therefore, once it is set, it is very hard to alter. The failure to invest in strong, high-quality retaining walls and foundations can lead to many costly issues later down the line.

Here at Wilsons Groundworks, we have a deep understanding of landscaping and groundworks, and can provide our services to a wide range of customers and a variety of different projects. When you’re working on a retaining wall, it’s important to choose a company you trust. We’ll ensure every project is carried out with utmost care and that every effort is made to create a design that meets your requirements, with a long-lasting final result.