Significantly slopped ground doesn’t lend itself to a patio, planting areas end up on a bank you can barely reach, and mowing anything steeper than a gentle incline becomes an event in itself.
Retaining walls solve all of that by holding back the soil on the higher side and creating flat, usable levels below.
In Scotland, where hilly terrain is common across Glasgow, Lanarkshire, and the wider Central Belt, sloped gardens are the norm rather than the exception.
Retaining walls come up in almost every garden project we take on that involves a meaningful change in level, and there’s considerable variation in what they look like, what they’re made from, and how they need to be engineered to do the job properly.
This guide covers the purpose of a retaining wall, the different types available, the main materials, design considerations, and what UK planning law says about building one. Written by terraced garden experts.
What is the purpose of a retaining wall?
A retaining wall is a structure that holds back soil on the high side while presenting a flat or near-vertical face on the low side.
Without one, soil on a slope shifts gradually downward under gravity, following what engineers call the angle of repose: the steepest angle at which loose material like earth or gravel stays stable without sliding.
Retaining walls use this principle to create level areas where none existed naturally.
In residential gardens, that means terracing a sloped plot to form flat lawn, patio, or raised garden bed areas.
In civil engineering, the same principles apply to road cuttings, embankments, and basement walls where the surrounding earth would otherwise push inward.
The structure that holds the ground in place doesn’t have to be a purely functional feature.
Landscaping walls designed well become part of the garden rather than something bolted onto it.
They add height, definition, and a sense of permanence that transforms how a space feels.
A well-built stone retaining wall can look as though it’s always been there.
When the materials are chosen to match the character of the site, a well-chosen material ties the wall into the wider landscape instead of sitting apart from it.
How retaining walls work
A retaining wall is designed to restrain soil and resist the lateral forces that the earth behind it exerts.
Those forces are called lateral earth pressure, and they act horizontally against the wall face rather than pushing down on it.
The wetter the soil behind the wall, the heavier it becomes and the more it presses outward.
Glasgow’s heavy clay soils are harder to manage than sandy or gravelly ones because clay holds water rather than draining it through, and the material behind the wall can carry considerably more pressure than its volume alone would suggest.
A retaining wall is designed to withstand that pressure through one of two approaches: sheer mass (a gravity wall, which resists the lateral pressure through its own weight), or structural reinforcement built into the base (a cantilever wall, which uses the weight of the retained earth to hold the structure in place).
The taller and heavier the retained material, the more engineering the wall needs behind it.
Drainage is the other side of how retaining walls work.
Water that accumulates behind the wall adds extra pressure, and that combination is responsible for a large proportion of retaining wall failures.
Properly designed retaining wall systems include weep holes, perforated drainage pipes, or granular backfill zones that allow water to escape rather than build up against the wall structure.
Types of retaining walls
Retaining wall types differ according to how they resist earth pressure, what they’re built from, and the scale of project they suit.
Here are some of the main ones that our team helps build every month.
Gravity retaining walls
Gravity retaining walls rely entirely on their own weight to resist the pressure of the material behind the wall.
They’re typically wider at the base and taper slightly upward, requiring no internal reinforcement, since the mass of the wall structure itself provides the stability.
Gravity walls are commonly used for small retaining walls in domestic gardens where retained heights are modest.
Dry stone walls are the simplest form: stone stacked without mortar, held in place by weight and the precise fit of each piece.
Block retaining walls of this kind are widely used in garden landscaping because they’re durable, relatively cost-effective, and can be faced in various materials to suit the design.
Retaining wall blocks specifically engineered for earth retaining are available with a slight backward lean (called batter) built into the profile, which helps resist the lateral earth pressure behind the wall.
Gabion walls
Gabion walls are built from wire mesh cages filled with stone, gravel, or other rock material.
Each gabion is a retaining structure in its own right, with the fill material inside the cage providing the mass and the wire mesh holding everything together as a unit. Walls are formed by stacking and connecting multiple gabion units to the required height.
One of the benefits of a gabion wall is its natural permeability.
Water drains through the stone fill rather than building up behind the wall, so gabion walls need very little drainage engineering.
They’re also flexible. The cages can settle slightly without cracking, which makes them more forgiving on unstable or variable ground than rigid concrete would be.
For garden retaining where the aesthetic matters as much as the function, gabions are worth serious consideration.
Filled with locally sourced stone, a gabion wall blends into the landscape and weathers naturally over time.
Plants establish well in the gaps between stones, and a well-chosen fill can make the wall read as a natural feature rather than a constructed one.
Cantilever retaining walls
Cantilever retaining walls use a completely different principle.
Rather than relying on mass, they use a stem and a base slab. This is typically formed from reinforced concrete.
The stem rises vertically to hold back the soil while the base slab extends horizontally beneath the material behind the wall.
The weight of the retained earth pressing down on that base slab provides the counterbalance that keeps the whole structure upright.
There are two ways these slabs are made.
Firstly, they can be cast-in-place and poured on site through the use of a steel reinforcement cage.
But if time is on the essence, precast concrete can be used instead.
Cantilever retaining walls suit large retaining applications where a gravity wall would be impractically wide or heavy.
Timber retaining walls
Timber retaining walls suit smaller-scale garden retaining where a natural appearance is wanted and the retained height is limited.
Railway sleepers along with pressure-treated hardwood posts and planks are the materials used most often.
For raised garden beds or low terraces, timber is a great solution.
The draw back to timber is its lifespan. Timber in contact with soil and rain will rot over time, even with treatment.
When we guide our client’s through timber and concrete options, we always lay out the positives and limitations of both, to help guide them towards a solution suited to their lifestyle and location.
Crib walls
Crib walls are assembled from interlocking precast concrete or timber sections, creating a grid frame that’s filled with granular material.
The criblock retaining wall is a well-known version: precast concrete headers and stretchers interlock to form a hollow box structure packed with stone or compacted fill.
Crib walls are permeable, which helps with drainage, and their open, textured face works well in commercial landscaping and larger amenity settings.
Retaining wall materials
The material for a retaining wall affects its structural performance, its appearance, and how long it lasts.
The main options are concrete, natural stone, brick, and timber, and the right choice depends on the retained height, the ground conditions, and the wider landscape design.
Concrete block and reinforced concrete
Concrete block is the most widely used material in domestic retaining wall construction.
Concrete masonry blocks are consistent in size, straightforward to lay, and can be reinforced with steel rebar where the retained height demands extra strength.
Block retaining walls of this kind suit the majority of garden projects where heights are manageable and a clean, finished face is wanted.
Natural stone
A stone retaining wall built from natural stone has an aesthetic appeal that’s hard to replicate with manufactured materials.
Sandstone, whinstone, and granite are all used in Scottish landscaping projects, and sourcing local stone gives a retaining wall a rooted, settled look that improves as the material weathers.
A retaining wall made from natural stone, whether dry-laid or mortared, suits traditional garden settings and period properties where character matters alongside structural performance.
Dry stone walls are self-draining and can last for centuries when built well. Mortared natural stone walls are more rigid and give a neater finish, suited to situations where the appearance needs to be precise rather than naturalistic.
Brick
A brick retaining wall suits formal and traditional garden designs, particularly where brick already features on the house or outbuildings.
Brick walls can be reinforced internally where height demands it, or built as solid masonry for modest retained heights.
A brick retaining wall can be constructed with a slight batter, a stepped profile, or a vertical face depending on the architectural design requirements and the character of the surrounding space.
Timber
Timber is the most accessible material for small retaining walls and raised beds.
Treated hardwood posts and planks or railway sleepers are the standard options. Timber is easy to build with and keeps costs down on straightforward projects, but it has the shortest lifespan of any of the materials listed here.
For a retaining wall that needs to last, concrete or stone may be a better long-term investment.
Retaining wall design
Poor design decisions in retaining walls are harder to fix once the wall is built.
Drainage and load calculations that weren’t done properly are the most common causes of failure, and both are far less costly to address at the design stage than after the wall has gone up.
A few factors matter more than anything else.
Height, slope, and soil type
Height is the primary driver of how a retaining wall needs to designed.
As the retained height increases, so does the pressure, and the wall structure needs to become progressively more supportive for the load.
The slope of the ground and the type of soil behind the wall also affect the load.
Clay holds water and expands when saturated, increasing pressure against the wall considerably more than free-draining sand or gravel would.
On any properly managed project, ground conditions are assessed before the wall is designed.
Drainage design
Drainage failures account for a large proportion of retaining wall problems.
Water building up behind the wall increases earth pressure, and the combination can overcome a wall that would otherwise have held perfectly well.
Weep holes at the base of the wall, a granular drainage layer behind it, and perforated drainage pipes all reduce the risk significantly.
Clay-heavy sites (which covers much of the Central Belt) need particular care.
Water doesn’t move through clay the way it does through sandy soils, so drainage needs to be engineered deliberately into the wall design rather than assumed to happen naturally.
Aesthetic appeal and landscape design
A retaining wall in a garden should be designed using materials that complement the house and the surrounding landscape rather than just solving the structural problem.
Natural stone suits older properties and naturalistic settings; concrete block suits contemporary designs; brick ties in with Victorian and Edwardian architecture.
Getting the architectural design right from the start gives you a wall that adds to the garden rather than detracting from it.
Material and finish choices made at the design stage are what determine whether a retaining wall reads as a considered feature or an afterthought.
Where retaining walls are used
Retaining walls are built wherever a change in ground level needs to be managed.
In domestic garden landscaping, the most common situations are:
Terracing sloped gardens
A series of level terraces cut into a slope, with retaining walls holding each level in place, transforms a difficult, unworkable plot into a series of distinct outdoor spaces.
Each level is only possible because a retaining wall is holding the ground back on the cut side, and most of the gardens we terrace across Greater Glasgow and Lanarkshire wouldn’t be usable outdoor spaces without them.
Each terrace creates usable area for lawns, patios, or planting that simply couldn’t exist without the wall holding the earth back.
Raised garden beds
Low retaining walls around the perimeter of a raised garden bed create planting areas at a better working height and a tidier, more considered finish.
The same principle scales from a small timber-framed vegetable bed to a large stone-walled kitchen garden.
Patio construction
Cutting a flat patio into a sloped garden means excavating the high side, and that excavated earth has to stop somewhere. A retaining wall on the cut side holds the ground back and keeps the patio level.
On most sloped Glasgow gardens, hard landscaping projects start exactly here.
Driveway construction
Where a driveway runs alongside a sloped boundary, a retaining wall holds the adjacent ground back to protect the surface below.
On steeply sloped plots, the driveway may sit well below the adjacent garden level, with the retaining wall on one or both sides forming an integral part of the structure.
UK law on retaining walls
Planning permission for a retaining wall in the UK depends primarily on its height and location.
Under permitted development rights, walls up to 1 metre high adjacent to a highway don’t generally require planning permission. Elsewhere on the property, that limit extends to 2 metres. Anything above those heights requires a planning application before work begins.
Conservation areas and listed buildings have stricter rules. If your property falls into any of these categories, check with the local planning authority before starting work. Building regulations are separate from planning permission and may also apply.
By choosing a qualified team who understand the rules and regulations of creating a retaining wall, you can save yourself from trouble down the line.
Retaining walls from GGM Landscaping
If you are looking for a team to manage and create a retaining wall in Scotland, you have come to the right place.
We design and build retaining walls across Glasgow, Lanarkshire, and Central Scotland as part of full garden and landscape projects.
Whether you need a single terrace wall to make a sloped garden workable or a series of levels across a more complex plot, we’ll survey the site, assess the soil and drainage conditions, and put together a retaining wall solution that fits the space and lasts.
Speak to our team about your project, by calling us on 07946 322717, or book your free garden consultation through our landscaping Glasgow page.