Retaining walls are built to keep soil in place that might otherwise move downwards. Retaining walls are often used in gardens to keep the soil on one side of the wall from slipping.
A retaining wall also enables you to create different levels of ground – as a feature – and can prevent soil erosion.
There are various types of retaining walls and you can choose the best one to suit your budget and the type of project you have in mind.
In this guide, we’ll break down the average costs of building a retaining wall, what affects the cost of the build, the best way you can save money and the best way to find and hire a tradesperson to build your retaining wall. Finally, we’ll answer some frequently asked questions.
How Much Does a Retaining Wall Cost?
The table below gives you estimated costs per square metre for various types of retaining walls.
|Wall Type||Estimated cost per||square metre by||wall height|
|1 metre||2.4 metres||4 metres|
|Gabion basket gravity wall||£350 per sqm||£340 per sqm||£435 per sqm|
|Masonry gravity wall||£290 per sqm||£350 per sqm||Unsuitable|
|Interlocking concrete block gravity wall||£240 per sqm||£320 per sqm||£440 per sqm|
|Concrete criblock gravity wall||£450 per sqm||£395 per sqm||£405 per sqm|
|Timber criblock gravity wall||£335 per sqm||£330 per sqm||£340 per sqm|
|Reinforced masonry cantilever wall||£330 per sqm||£280 per sqm||£360 per sqm|
|Precast concrete cantilever wall||£350 per sqm||£270 per sqm||£330 per sqm|
The prices are based on the construction of around 50 square metres of wall.
In much smaller areas the square metre price may increase slightly.
The table shows construction prices for the wall itself but there are other costs to the project that you should take into account.
Retaining walls can require significant below ground construction as well as work above the ground. The ground will have to be excavated to the required depth in advance of the wall being built.
The cost for this falls into two categories: the costs to physically excavate the ground and the cost of the removal of the spoil.
If the wall is not particularly long then the excavation could be done manually. A ground worker will typically charge between £120 and £200 a day for this type of job, depending on where you live.
The situation changes if you need to construct a retaining wall of any significant length or height. It may no longer be practical to excavate manually.
For most residential projects the excavation can be achieved using a mechanical mini digger.
These can be hired with or without an operator. A digger with an operator will cost around £250 to £350 per day.
You can also hire a mini digger and do the job yourself. The hire company will deliver the digger and you can get stuck in once it arrives.
Although legal to operate on private land without a license, be sure to understand any insurance policy supplied through the hire company.
In most cases, it will be more efficient and a lot less stressful to hire one with an operator.
Soil Disposal Costs
Disposal of the spoil is another cost to consider. Soil is very heavy and you may be surprised by how much will need to be removed if your retaining wall requires deep excavation.
For small scale projects skip hire is an option to consider. Skips can be hired from £90 to £360 depending on size and the duration of the hire period.
A more economical way of disposal for large amounts of soil is to have it collected by a grab lorry, known as a ‘muck away lorry.’ As long as the lorry can gain access to the spoil (it can reach up to eight metres with the grab bucket), this will be far more cost-effective than skip hire.
The lorry will be able to remove up to 14 cubic metres of soil in one go. This is more than three large skips are capable of holding.
Through this method, you save time and the effort required to load the skips. A grab lorry of this type will be around nine feet wide and 22 feet long.
Smaller lorries and the ability to book a part load is often available. Prices grab lorry hire start at around £150.
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What Affects the Costs of Building a Retaining Wall?
Several factors will have an impact on the final cost of building a retaining wall.
It is necessary to know whether the soil is sand or clay. Clay soil expands and shrinks with water absorption, therefore, a builder may choose concrete as a material to use in clay soil.
Concrete will handle the pressure of the expanding clay better than timber. A cantilevered wall may be chosen rather than a gravity wall.
Sandy soil gives natural drainage and therefore there is less pressure on the wall. Gravity wall types can be used as well as concrete or timber
Your slope will determine how deep you have to excavate a base trench and you will need to step the wall up using paver base which will give you a level surface. If the slope is more than a 3:1 ratio, you will need to consult a structural engineer because methods to create greater strength are required.
The type of retaining wall you choose to have built with an impact on the cost.
Gravity walls are made with concrete blocks, cast-in-place concrete, or stone. They can also be made with steel baskets filled with stone, which are called gabion basket retaining walls
A heavy material must be used because the wall resists pressure entirely by its own weight. Gravity walls are normally used when the height is between one and 10 feet.
It will depend on the specifications whether or not you can have a gravity wall up to 10 feet. The most usual height for a gravity wall is four feet
Cantilevered walls are another option to consider and are made from reinforced concrete to act as a beam.
To construct a cantilevered wall, you need firm foundations to build a strong structural base. The design of the cantilevered wall means that less concrete than a gravity wall is needed.
Criblock walls are made with concrete or timber and are another option to consider. They are designed in frames that lock into each other.
The frames are then filled with stone. Criblock walls are often used in landscape gardening.
Choice of Building Material
The choice of building material used will also have an impact on the final cost. We examine a few of the materials available to use in a retaining wall.
- Stone – Stone is often used for its strength and aesthetics because it looks more attractive than many other materials.
- Masonry bricks – Using masonry bricks is the least expensive method of building a retaining wall. The brickwork wall is a cavity wall (two walls with a gap in the middle). Concrete is placed in the gap between the walls to create strength.
- Concrete criblock – Concrete criblock is made of concrete and the inside of the frame is filled with stone.
- Timber criblock – Timber criblock is the same as concrete criblock, but the material used is timber, rather than concrete.
- Precast concrete – precast concrete retaining walls are delivered ready-made in blocks that are set onto a level base.
- Reinforced soil – This type of soil is reinforced by using elements mixed with the soil that provide strength and flexibility. In Mechanical Stabilised Earth (MSE) the earth is reinforced by using layered horizontal mats.
Structural Engineering Fees
If you need to have a structural engineer come to your property to assess the site, then this will increase the final cost of paying for a retaining wall.
Structural engineers charge, on average between £60 and £120 per hour. They may offer some services for a flat fee, particularly if the job is quite extensive and could require drawings or surveys.
If the access to the site of your wall isn’t awkward or difficult you won’t need to pay anything extra in labour charges. However, if site access is complicated then you will likely need to pay more for the professional to come to your property.
If a machine like an excavator, for example, can’t be used then the work will need to be done with a mini digger or by hand. Both methods will take longer and cost more.
If you live in a central area that’s easy to get to by car or public transport, a contractor’s travelling costs will be less than if you live in a remote location.
It’s beneficial to try and source professional tradespeople in your area, so you don’t have to face additional travelling fees.
Size of the Wall
The height of the wall will affect the price of building it. It is cheaper to install a wall that’s four feet high than it is to install a 10-foot wall.
How Can I Save Money on a Retaining Wall?
If you are building a small wall, you could do your own excavation which will save paying groundworkers.
It’s not recommended you attempt DIY when it comes to larger walls because of the need to hire an excavator.
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How Do I Find and Hire Someone to Build a Retaining Wall?
Ask family, friends, and work colleagues if they know of any professionals who could help you, or if they have recently had similar work done.
If you can’t find anyone suitable from personal recommendations, then HouseholdQuotes can help you. We’ll find tradespeople in your area to give you no-obligation quotes, with our quick and easy search function!
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Ensuring the Professional Is the Right Fit
It’s a good idea to make sure you have a list of questions ready to verify that the tradesperson you want to hire is the right fit for you. Use the questions below to make sure they’re up to the job:
- What experience do they have? It’s always useful to know if they are a well-established company or they are just starting out. You might find that a newer company is slightly cheaper, or you may prefer to pay more for experience.
- Have they got customer feedback and photographs of any work they’ve done in the past? The tradesperson may have a portfolio to show you, or they may direct you to their website. Websites often have case studies, photographs, and customer testimonials.
- Do they have public liability insurance? All tradespeople should have public liability insurance to protect the tradesperson and yourself from any claims for injury or damages.
- Are they a member of any trade associations? Trade associations will only grant membership to tradespeople with a good work record and a high standard of workmanship.
- Do they have any qualifications or certifications?
- Do they organise the disposal of any waste materials, or will you need to organise that yourself?
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Use the below checklist to make sure you’ve got everything ready to hire the best tradesperson for the job:
- Decide on the type of retaining wall you want to be built
- Get at least three quotes from different tradespeople
- Contact your local planning department and ask them about planning permission and building regulations
- Choose your tradesperson
- Arrange for the work to begin
Frequently Asked Questions
Do I Need Planning Permission or Building Regs Approval to Build a Retaining Wall?
If you want to build a wall that’s higher than planning regulations, you will need to seek the advice of your planning department. In some areas, taller walls are acceptable if they are in sheltered areas and piers have been used in the construction.
If the retaining wall is a party wall, you will need to inform your neighbour.
You will also need planning permission if your home is a listed building, or you live in a conservation area.
Height and thickness regulations depend on where in the UK you live. There is a useful chart available on the planning portal website to help you see what regulations apply to you.
Do I Need a Structural Engineer to Design a Retaining Wall?
This is because, to be safe, the wall will need to be a certain strength. Structural engineers are experts in the safety and strength of building structures.
How Do I Know if I Need a Retaining Wall?
- You have downhill soil erosion
- Your home is at the bottom of a hill
- You want usable beds out of a sloping garden
- You want to make usable terrain from a slope
How Much Does It Cost to Build a Garden Wall?
- £500 to £900 – One metre high and four metres long
- £1,000 to £1,800 – One metre high and eight metres long
- £1,500 to £2,700 – One metre high and 12 metres long