Retaining Wall Cost Calculator

A retaining wall holds back soil where the ground level changes, turning a sloping garden into usable, level spaces. Retaining walls can be simple garden features or serious structures, and the cost depends on the height, the material and, above all, how much soil they hold back.

This guide covers typical UK costs and the key things to get right. To estimate your own project, use the retaining wall cost calculator.

Retaining wall costs per m²

Retaining walls are usually priced by the square metre of wall face (length × height), including footings and labour. Typical 2026 prices are:

Prices rise with height, because taller walls need deeper foundations and more reinforcement. Difficult access and removing large amounts of soil also add cost.

A worked example

An 8 metre long timber sleeper wall retaining 0.9 metres of soil, with drainage behind it:

• Wall face: 8m × 0.9m = 7.2m²
• Sleeper wall: 7.2m² at a typical £200 per m² = £1,440
• Drainage: 8 metres at about £30 per metre = £240
• Typical total: around £1,680

You can change the length, height and material in the retaining wall cost calculator.

The main types of retaining wall

Timber sleepers

Sleepers are popular for raised beds and low walls in gardens. They're quick to install and have a natural look. Use new, pressure-treated timber rather than old railway sleepers, which may contain creosote. Expect a lifespan of 15 to 25 years. Walls over about 1m usually need steel posts set in concrete to stop them leaning.

Gabion baskets

Gabions are wire cages filled with stone. They're heavy, free-draining and flexible, which makes them good at coping with ground movement. They suit contemporary and rural gardens, and the fill can be chosen to match local stone.

Concrete block and brick

Block walls, often finished with render or faced with brick, are strong and long-lasting. They need a proper concrete foundation and, for taller walls, steel reinforcement. Brick facing looks attractive and can match the house.

Reinforced concrete

Poured concrete walls with steel reinforcement are the strongest option, suitable for large changes in level and walls near buildings or driveways. They're usually designed by a structural engineer.

Why drainage matters

The biggest enemy of any retaining wall is water. After heavy rain, the soil behind the wall becomes saturated and much heavier, pushing harder against it. Without drainage, that pressure can make the wall bulge, crack or collapse.

Good practice usually includes:

• A layer of free-draining gravel directly behind the wall
• A perforated drainage pipe at the base, leading water away
• Weep holes through solid walls so water can escape
• A membrane to stop soil clogging the drainage stone

Drainage adds a modest amount to the cost but is the single best way to make a wall last.

When you need a structural engineer

As a general rule, any wall retaining more than about 1.2 metres of soil should be designed by a structural engineer. You should also get professional advice, whatever the height, if:

• The wall is near a building, driveway or road
• There's extra load at the top, such as parking, a shed or another wall
• The ground is clay, sloping steeply or prone to water
• The wall is on or near a boundary with a neighbour

A badly designed retaining wall can fail suddenly and cause serious damage, so this isn't the place to cut corners.

Planning permission and other rules

In England, you can usually build a garden wall without planning permission if it's no more than 1 metre high next to a highway, or 2 metres high elsewhere. Retaining walls that significantly change ground levels, especially near boundaries, may need permission, so check with your council.

You should also consider:

• The Party Wall Act, which may apply if you're building on or near a boundary or excavating close to a neighbour's building.
• Listed buildings and conservation areas, which have stricter rules.
• Building Regulations, which don't usually cover garden walls but may apply if the wall supports part of a building.

Ways to keep costs down

1. Use terraces. Two lower walls stepped back from each other can be cheaper and safer than one tall wall.
2. Choose materials to suit the height. Sleepers are great for low walls but not for big level changes.
3. Reuse soil on site where possible to reduce removal costs.
4. Get the design right first. Fixing a failed wall costs far more than building it properly.

Questions to ask a contractor

• How deep will the foundations be?
• What drainage will be included behind the wall?
• Will the wall need reinforcement, and who designed it?
• What happens to the excavated soil?
• What guarantee do you offer?