Retaining walls with timber: using sleepers, edging, and piles for erosion control

The UK is getting rainier. Our country has seen a 17% increase in extremely wet days, with sudden, high rainfall becoming more common throughout the year. This change to our climate poses a fair few new challenges, one of which is an increase in soil erosion and movement. To prevent landslides and stop our landscapes from crumbling, it is absolutely vital that we see an uptick in erosion control. This is where timber comes in.

Whether you are in commercial construction or worried about your garden, the right timber products can create sturdy retaining walls and keep soil erosion at bay.

What Are Timber Retaining Walls?

Retaining walls are installed for the sole purpose of holding soil in place. You might, for instance, have a steep verge of earth and grass next to a public footpath. With extreme rainfall, this soil can become less stable, increasing the likelihood of it sliding onto the footpath and blocking the walkways, or injuring pedestrians. A retaining wall provides vital structural support for the verge, holding the earth in place to prevent landslides and erosion even in periods of high rainfall.

This system is not just useful in public spaces, but also in private landscaping. Retaining walls are often used in sloped gardens, for instance, to create level terraces, making outdoor areas more accessible and usable. They can also be used to separate planting zones, build raised beds and prevent soil from spilling onto patios or pathways, all while contributing to erosion control.

What’s The Difference Between Class 1 and Class 2 Durability Timbers?

Durability Class 1 Timbers

A lot of people make the mistake of choosing simply between hardwoods and softwoods when building a retaining wall. The reason we would advise against this is that not all softwoods are less durable or strong than hardwoods, and not all hardwoods have the durability you need. Instead, we would advise looking at their durability classes, which categorise timber species depending on their resistance to external threats.

If your retaining wall is in use class 4 – direct contact with the ground (as itis likely to be), you will be best suited to a durability class 1 timber. These are some of the ground projects where timber comes in direct ground contact, and can deal with constant dampness and the threat of rot with ease. They are also more resistant to fungal infestation and rot, making them easier to maintain over the years.

Some of the durability class 1 timbers we recommend for retaining walls include Greenheart and Ekki.

Durability Class 2 Timbers

If you would prefer a wider range of more accessible timbers from which to choose, you can still choose a durability class 2 timber for your retaining wall. Oak, for example, is a durability class 2 but is still highly resistant to decay and has a long lifespan even when untreated. Cedar, Cumaru, and Iroko are other durability class 2 timbers we would recommend for retaining walls.

Treated Timbers

When moving outside durability class 1 and 2 timbers, you will need to treat your species in order to make it suitable for outdoor, ground contact use. But there are perks to be had from using a treated, less durable wood. Pine, for example, is lighter and easier to work with than the more durable timbers, and when coated with a natural Silica compound to create OrganoWood, it becomes far more resistant to rot and infestation.

Why Use Timber for Retaining Walls?

Timber offers a unique combination of natural strength, workability and sustainability. It blends seamlessly into our country’s natural landscapes, making it ideal for projects where the goal is to control erosion without compromising the look and feel of the space.

Let’s take a closer look at why timber is so popular when building retaining walls:

• Durability: The right timber species will easily handle direct contact with soil and moisture, removing the need for costly treatments and maintenance. A durable timber retaining wall can last for upwards of 25 years, making it a long-lasting choice for landscaping.
• Flexibility: Timber is easy to work with and can be cut, planed and installed with ease. From DIY to professional construction in a public space, this makes for more streamlined projects which suit the surrounding environment perfectly.
• Cost-effective: With plenty of budget-friendly timber species available, you can build retaining walls which do not break the bank. This is often far cheaper than masonry or steel.
• Sustainability: Renewable and biodegradable, timber is a great choice for eco-friendly projects. It has a low (often negative!) carbon footprint thanks to its unique carbon sequestration properties.

Whether you are reinforcing a bank or protecting your garden against water damage, timber is a smart choice for your retaining walls.

Timber Piles for Structural Support

Timber piles form the foundation of retaining walls, creating a sturdy and supportive structure to prevent erosion. These durable timber poles are driven vertically into the ground, holding back soil and stabilising the earth deep beneath your wall to form the foundation of your construction. When choosing timber piles for erosion control, we recommend a naturally durable timber species which is able to survive being submerged in the earth, e.g. Greenheart, Ekki or Opepe

Timber Edging for Containing and Shaping Soil

Timber edging is made using durable boards of timber and can be fixed to your timber piles. When creating a retaining wall, your edging will outline the area you want to contain, building from the ground up for a supportive and precise border. The purpose? To prevent loose soil from spilling out onto lawns and pathways, keeping your earth exactly where it should be.

Timber Sleepers for Sturdy Walls

Timber sleepers are one of the most popular and reliable options for building strong, long-lasting retaining walls. They are super thick and made from dense, durable timber species, such as Oak and Ekki, bringing plenty of strength to your landscaping project. Install your sleepers horizontally and fix them behind timber piles for a sturdy barrier which is capable of holding back a substantial amount of soil.

Budget-Friendly Timber Options

When weighing up the cost of different timber species, the more durable options tend to come with a higher price tag. However, it is important to remember that you will save money on maintenance and treatments over the years, and with a projected lifespan of 25+ years at least, the cost-per-year of your retaining wall will be significantly less than if it is made from a cheaper timber which rots quickly.

If you are looking to save money or have a tight budget, we recommend chatting with a member of our team. We can help you find a timber species which suits your price range but does not make you compromise on quality.

Choose the Right Timber Species

We have mentioned it a few times in this guide, but it is worth noting again: the success of your retaining wall depends entirely on the timber species you choose. Not sure what to go for? We can help. Our EcoChoice experts will be happy to chat more about what you need for your retaining wall and match you with the right timber species and products to get the job done properly.

Chat to our team about your timber options.