Concrete retaining walls: types, dimensions, concrete grade, prices and fibre reinforced precast

A concrete retaining wall holds back soil or bulk material where two ground levels meet. Most are precast L- or T-shaped units whose base sits under the retained soil, so the soil's weight keeps the wall in place. Standard heights run from 30 to 300 cm; a 100 cm unit costs indicatively €90–160 per linear metre ex works (2026 price level).

Fibre reinforced precast makes retaining wall units slimmer, more impact-resistant and free of corrosion. This guide covers the main types (precast L- and T-shaped units, reinforced concrete cast in situ and mass concrete), the section of a retaining wall, a table of dimensions, weights and prices per height, the right concrete grade, upstand walls on slabs, and installation with proper drainage.

What is a concrete retaining wall and how does it work?

A retaining wall (also called an earth-retaining structure) keeps soil, sand or other loose material in place where two levels meet: a raised garden, a loading pit, a silage clamp or a storage bay. It is sometimes loosely called a cement retaining wall, although cement is only the binder in the concrete. Unlike a masonry wall or fence, a retaining wall must withstand permanent earth pressure: a horizontal load that increases with the retained height and with whatever stands on top, such as a terrace, driveway or a loading shovel driving past.

Precast concrete retaining walls solve this through their shape: the horizontal base extends beneath the retained body of soil, so the weight of the soil itself presses the wall into place. The higher the wall and the heavier the surcharge, the larger the base and wall thickness are dimensioned. This makes the retaining wall fundamentally different from stacking blocks (which rely purely on their own mass) or a sheet pile wall (which derives its stability from its driven depth).

Whatever the type, the retaining wall structure has to pass three stability checks. It must not overturn about its toe, it must not slide along its base, and it must not overload the ground beneath it (bearing capacity). The structural engineer verifies these with the earth pressure to Eurocode 7 (EN 1997-1) and designs the concrete and any reinforcement to Eurocode 2 (EN 1992-1-1).

Retaining walls in standard heights are mostly supplied precast: cast in steel moulds, cured under controlled conditions and delivered by lorry. Within our pillar applications and target groups for fibre reinforcement, the retaining wall is thus a typical precast product, with all the advantages that fibre reinforcement offers in precast concrete elements.

Concrete retaining wall section: stem, heel, toe and shear key

A cross-section through a concrete retaining wall shows four parts that work together, plus a drainage zone behind the wall:

• Stem: the vertical wall that takes the earth pressure. Its thickness is constant or tapers towards the top, because the bending moment is greatest where the stem meets the base.

• Heel: the part of the base under the retained soil. The soil resting on the heel holds the wall down and counteracts overturning.

• Toe: the part of the base on the visible side, in front of the stem, which adds resistance to overturning and spreads the load on the ground. An L-unit with its base fully on the soil side has no toe.

• Shear key: a downstand rib under the base that prevents sliding under high horizontal loads, as in loading pits and silage clamps.

• Drainage zone: the free-draining backfill directly behind the stem, which keeps water pressure off the wall (see installation below).

For retaining wall dimensions, a few indicative rules of thumb help at sketch stage. Published ranges of precast L-units have a base of roughly 0.5 to 0.6 times the unit height, for example a 1,000 mm unit on a 500 mm base or a 3,000 mm unit on a base of 1,500–1,700 mm. For a reinforced cantilever wall cast in situ, the base is typically 0.4 to 0.6 times the retained height and the stem around 200–300 mm thick up to about 3 m retained height, thicker above that. Precast stems can be much slimmer: low garden units of 30–40 cm have a wall thickness of around 6–8 cm.

These figures are indicative and only suitable for a sketch design. The actual section always follows from the engineer's calculation for the specific soil, height and surcharge.

Types of concrete retaining walls

The shape of the unit determines how much earth pressure a retaining wall can take and how it is placed. Precast retaining walls (L-shaped, T-shaped and units with a shear key) cover most of the market, with standard ranges up to about 3 m and heavy agricultural ranges up to 5–6 m. On curved alignments, for very tall walls or where the wall is integrated with a basement, reinforced concrete retaining walls are cast in situ. For low walls, a mass concrete gravity wall is the simplest option.

L-shaped precast concrete retaining walls

L-shaped concrete retaining walls are the most widely used type: a vertical stem with a base on one side. As standard, the base is placed beneath the soil to be retained (base towards the soil side), so the soil stabilises the wall. Where there is no room to dig into the slope, against a site boundary for instance, versions exist with the base on the visible side, usually combined with heavier dimensioning. Unit widths are typically 30, 40, 50 or 100 cm, so any wall length can be built up to fit.

In the UK, these precast concrete retaining wall units are often sold as L walls or precast concrete walling. Three installation variants are common: freestanding units stand on a prepared bed, bolt-down units are fixed to an existing concrete slab with resin anchors, and cast-in units have their base connected into a new floor slab. Indicative L-shaped precast concrete retaining wall prices per height are given in the table further down.

T-shaped retaining walls and walls with a shear key

For greater retained heights or heavy surcharges (traffic, storage, silage), the choice shifts to T-shaped retaining walls: the stem stands in the middle of the base, which extends to both sides. This distributes the forces more favourably and limits the overturning pressure on the toe. A variant is the retaining wall with a shear key — a vertical rib beneath the base that blocks sliding across the foundation under high horizontal loads, as in loading pits and silage clamps.

Reinforced concrete retaining walls cast in situ: cantilever and counterfort

A reinforced concrete retaining wall cast in situ works on the same cantilever principle as a precast L- or T-unit, but it is poured on site in formwork around a tied reinforcement cage. The reinforcement mesh and cages in stem and base take the tensile forces caused by the earth pressure. Cantilever walls are generally the economical choice up to a retained height of roughly 7–8 m (indicative; sources differ). Above that, counterfort walls take over: triangular webs at regular intervals behind the stem tie stem and heel together and reduce the bending moments in both.

Casting in situ makes sense for curved or irregular alignments, walls integrated with a basement or building, very large heights and sites without crane access. The trade-off is time on site: excavation, formwork, fixing the reinforcement, pouring and curing are separate stages, whereas a precast unit arrives with factory quality and goes in with a single lift. Fibres can partly replace the cage in stem and base; for taller walls, the structural engineer determines the ratio of fibres to bar reinforcement.

Mass concrete retaining walls (gravity walls)

A mass concrete retaining wall is unreinforced and resists earth pressure with its own weight alone. That calls for a wide base, typically 50–70% of the retained height as an indicative rule of thumb, and therefore much more concrete per metre than a cantilever wall. Gravity walls are economical for low walls, roughly up to 1.5–2 m (some sources go up to about 3 m; indicative). The advantage: without reinforcement, there are no cover or corrosion issues.

Stacking blocks (interlocking concrete blocks, often cast from leftover concrete) are a modular variant of the gravity wall; fibres in the mix improve their edge stability. For higher walls, the precast L-unit is the more efficient choice: it uses the retained soil as ballast and needs far less concrete.

Corner units, infill units and finishes

For a closed arrangement, manufacturers supply corner units (internal and external 90° corners), infill units in non-standard widths and units with mitred or chamfered heads. Alongside standard grey concrete, retaining walls are available in anthracite, or with an exposed-aggregate or coated face for garden applications. Used retaining walls are also traded — but do check the condition of lifting anchors and edges before putting them back into service.

Concrete upstand walls on a slab

A concrete upstand wall is a low wall that rises from the edge of a concrete slab or foundation, for example around a silage slab, a storage bay, a manure or salt store, a loading area or a bund. There are three ways to build one:

• Cast monolithically with the slab, using starter bars that tie the wall into the monolithic concrete floor slab.

• Precast bolt-down L-units, fixed to an existing slab with resin anchors.

• Cast-in units, whose base is tied into a new floor slab as it is poured.

Upstands take impact from loading shovels and, on farms, attack from acidic silage effluent. That is why corrosion-free fibre reinforcement and a sound connection between wall and slab are the points to specify with care.

Concrete retaining wall dimensions, weight and price per metre

The values below are market indications per linear metre for standard grey L-shaped precast retaining walls: ex works, excluding transport, installation and VAT, 2026 price level and depending on manufacturer, wall thickness and base dimensions. Use them for budgeting, not for ordering. Low garden units of 30–40 cm have a wall thickness of approx. 6–8 cm; from about 80 cm height, mechanical placing with a crane or telehandler is the norm.

The price per project is further determined by corner units, colour and fair-faced options, transport distance (heavy units mean fewer metres per load) and the crane deployment during installation. If you have a retaining wall installed, allow for installation costs on top of the unit price; these depend heavily on accessibility and groundworks, so always ask for them as a separate item.

For UK readers, a comparison: UK cost guides for 2026 put an installed in-situ reinforced concrete cantilever wall of about 1.5–3 m at roughly £400–£900+ per linear metre, and excavation, drainage and backfill can account for a large share of that. This is an installed price for a cast wall, not a supply price for precast units. Precast supply prices vary per manufacturer, so ask for a supply price and an installed price separately.

What concrete grade for a retaining wall?

The concrete grade for a retaining wall follows from the exposure class and the structural design. For reinforced retaining walls cast in situ in the UK, C28/35 to C32/40 is common (designated concretes RC28/35 to RC32/40 under BS 8500), with the permanently damp soil side typically in exposure class XC2. These are indicative values: the engineer specifies the concrete to EN 206 and BS 8500.

• In-situ reinforced walls (domestic and commercial): commonly C28/35 to C32/40; taller walls or heavier surcharges may call for a higher class.

• Frost and de-icing salts (road edges, car parks, yards): XF exposure classes, often with air-entrained concrete or a higher strength class.

• Precast retaining wall units: factory concrete in higher strength classes, with UK manufacturers declaring up to C50 for heavy-duty units. Ask for the declared class under the CE marking to EN 15258.

• Silage clamps and manure stores: chemical attack from acidic effluent (pH around 3.8–4.5) puts these walls in exposure classes XA2/XA3, which calls for dense concrete with a low water/cement ratio. In the UK, silage clamp walls are designed to BS 5502-22.

• Mass concrete gravity walls: unreinforced, so there are no cover or corrosion requirements; the strength class is set by durability and bearing, not by reinforcement.

Fibres do not change the strength class. What they add is residual flexural strength, determined with the beam test to EN 14651, which the engineer can use in the design.

Applications: from garden to silage clamp and civil engineering

The same unit shapes serve three very different markets, each with its own governing load: aesthetics and ease of installation in the garden, chemistry and impact loading on the farmyard, and dimensional accuracy and environmental score in civil engineering.

Retaining a change in level in the garden

In the garden, the retaining wall is the clean-lined alternative to a slope, gabion or timber wall: it holds back a change in level in one straight line and needs no maintenance. Think of a raised terrace, a sunken seating area or a driveway that lies lower than the garden. Timber (such as azobé) eventually decays in contact with soil and moisture; concrete does not. If you combine the retaining wall with a cast terrace, also read how to build a concrete terrace floor without reinforcement mesh — the same fibre technique, one consistent material palette.

For landscapers, the installation advantage is considerable: units up to around 60 cm can be set with a mini crane or vacuum lifter, and finishing work can continue immediately after backfilling and compacting. One point of attention: check the planning rules with the local authority — an earth-retaining structure does not automatically fall under the rules for boundary fences.

Agricultural: silage clamp walls and storage

On the farmyard, retaining walls are the standard solution for silage clamps, silage slabs with upstand walls and bays for manure or bulk storage. Silage clamp walls are typically 1.5–3 m high and take heavy punishment: lateral pressure from compacted silage, impacts from the loading shovel and silage block cutter, and silage effluent with a pH of around 3.8–4.5 that attacks unprotected concrete and, above all, rusting reinforcing steel. This is exactly where corrosion-free reinforcement pays off — the full context of floors, silos and yard paving is covered in fibre reinforced concrete for the agricultural sector.

Civil engineering and site layout

In civil engineering, retaining walls appear at slope transitions, loading and unloading pits, recycling centres and segregated bulk storage at municipal depots and concrete plants. What counts here is impact resistance (daily loading and unloading with machinery), dimensional accuracy for relocatable arrangements and, increasingly, the environmental score of the unit in the tender.

Fibre reinforced precast retaining walls: why fibres instead of mesh?

Traditionally, reinforced concrete retaining walls get reinforcement mesh or tied cages in the stem and base. Fibre reinforcement replaces that mesh wholly or largely: the fibres go into the mixer and are thus automatically distributed through the full cross-section. For precast retaining walls this delivers four practical advantages:

• No cover errors and no corrosion: a retaining wall stands permanently in moist, often acidic soil. With traditional reinforcement, a displaced mesh or a shrinkage crack leads to corrosion of reinforcing steel and spalling concrete; synthetic and basalt fibres do not have that mechanism.

• Higher impact resistance: fibres in base and stem limit shrinkage cracking and increase edge stability and impact resistance during the daily loading and unloading work against the wall.

• Slimmer, lighter units: less cover and reinforcement that works through the entire cross-section allow a slimmer stem. That saves weight, and therefore transport costs and crane capacity per metre of wall.

• Lower environmental cost indicator (MKI): a few kilos of fibre replace tens of kilos of reinforcing steel. For a comparable precast wall element, a precast internal wall, an MKI reduction of up to 93% has been demonstrated with synthetic fibre (from €17.51 to €1.13). That is not a measured retaining wall result, but it shows the order of magnitude; for tenders with environmental criteria, the gain can be calculated directly.

Which fibre fits depends on loading and environment. Steel fibres for concrete retaining walls such as the MPZG HT+ 35/0.55 (10–35 kg/m³, tensile strength 1,345 N/mm²) deliver the high residual strengths for heavily loaded walls and great retained heights. A structural macro fibre for earth-retaining structures such as TwistR (100% polypropylene, 2–6 kg/m³) is the corrosion-free choice with the greatest MKI gain for garden and site units. And for retaining walls in permanently wet or acidic ground, silage clamps first and foremost, a corrosion-free basalt fibre for retaining walls combines high tensile strength with high temperature resistance, and is corrosion-free and chemically inert.

How to choose between steel fibres or synthetic macro fibres is covered in a separate comparison; for the amounts per cubic metre, see the concrete fibre dosage guidelines.

Steel fibres are covered by EN 14889-1 and polymer fibres by EN 14889-2; the residual strength for structural applications is determined with the beam test to EN 14651 (background in EN 14889 and CE marking for fibre concrete). The precast retaining wall elements themselves are CE marked under EN 15258. For fibre reinforced retaining walls, ask the manufacturer for those performance classes, so the structural engineer works with validated values. Note: lifting anchors and any local edge reinforcement remain steel even in fibre reinforced units, because the lifting phase produces concentrated forces that call for localised reinforcement.

Installing a concrete retaining wall: foundation and drainage

A retaining wall is only as good as its base. Low units (up to around 60–80 cm) usually stand on a compacted and levelled bed of stabilised sand or bedding mortar 10–20 cm thick; taller walls and walls with a surcharge require a dimensioned foundation layer or cast ground beam. How to build such a cast foundation with fibre reinforcement is covered in reinforcement for foundations.

Installation itself follows fixed steps: excavate down to firm, load-bearing ground; place and compact the foundation bed; set the units with a crane or telehandler (note the weight per unit from the table above); connect or seal the joints; and finally backfill and compact in layers on the soil side. Two points are most often underestimated in practice:

• Drainage: water behind the wall increases the pressure considerably, because saturated backfill pushes much harder than drained soil. A typical detail is a free-draining zone of gravel wrapped in geotextile directly behind the wall, with a perforated land drain of around 100 mm at the base that discharges to a lower point. In-situ walls are also given weep holes, typically 75–100 mm in diameter at roughly 1–1.5 m centres. These are indicative details that keep the loading within the design; the engineer's drawing governs.

• Surcharge: a driveway, terrace or moving machine above the wall counts fully towards the earth pressure. From a retained height of around one metre, or sooner with traffic or storage on top, the choice of unit should be underpinned by a structural engineer's calculation (earth pressure to Eurocode 7).

Between precast units, seal the joints or cover them on the soil side with a strip of geotextile, so that fines from the backfill do not wash through.

Buying precast retaining walls or producing them yourself?

For buyers such as landscapers, contractors and farmers, the practical route is: determine retained height and surcharge, budget with the indications above and ask the manufacturer about fibre reinforced versions with EN 14889-certified fibres; in wet or acidic ground, ask explicitly for a corrosion-free fibre type. Before you order a precast retaining wall, also ask the supplier for:

• the CE marking under EN 15258;

• the declared concrete strength class and exposure class;

• the permitted surcharge per unit (kN/m²);

• for fibre reinforced units, the fibre type with its EN 14889 declaration.

For precast manufacturers, the retaining wall is one of the most rewarding products to switch to fibres: series production, predominantly evenly distributed loading and direct gains in mould turnaround and MKI. We are happy to think along about fibre type and dosage per unit height. Run through the selection tool for an initial direction or request a quotation with dosage advice based on your unit drawings.