C8/10 to C40/50 Mix

Work out concrete volume, grade, nominal mix ratio, cement bags, sand, aggregate, water and 2026 UK ready-mix cost for domestic slabs, foundations, drives, reinforced concrete and structural works.

C8/10 to C40/50 Concrete Grade Guide UK 2026

Concrete grades used in the UK are commonly written asCylinder/Cube strength classes, for exampleC25/30. The first number refers to the characteristic cylinder strength in MPa or N/mm², and the second number refers to the characteristic cube strength at 28 days. In practical UK ordering language, domestic customers may also hear terms such as GEN, ST and RC mixes. These are convenient descriptions, but the safest specification is still a performance-based ready-mix concrete specification aligned withBS EN 206and the UK complementary standardBS 8500.

This page is designed as a practicalconcrete mix design guide UKfor estimating quantities and early budgets. It helps homeowners, builders and guides compare C8/10, C12/15, C16/20, C20/25, C25/30, C30/37, C35/45 and C40/50 grades, understand common uses, and work out the difference between a simple site-mix ratio and a certified ready-mix order. For any structural concrete, retaining structure, reinforced beam, suspended slab, basement, pile cap or commercial project, final specification should come from a structural engineer or concrete supplier.

2026 UK Standard Context

UK concrete is normally specified with reference to BS EN 206 and BS 8500. BS 8500 is the UK complementary standard that gives national rules and guidance for specifying concrete, including durability, exposure classes and constituent material requirements. See theConcrete Centre standards overviewandBSI BS 8500-1:2023for the formal standard reference.

Domestic Concrete

C16/20 to C25/30 usually covers paths, shed bases, light slabs, driveways and strip footings when conditions are simple and loads are modest.

Structural Concrete

C30/37 and above is commonly used where reinforcement, design loading, durability exposure or engineer control is required.

Durability Matters

Concrete grade alone is not enough. Exposure class, water-cement ratio, cement type, cover and curing all affect long-term performance.

• Grade: C8/10; Cylinder / Cube Strength: 8 / 10 MPa; Common UK Name: GEN 0 / Lean mix; Typical Use: Blinding, kerb backing, cavity fill, non-loadbearing mass fill; Specifier Note: Non-structural
• Grade: C12/15; Cylinder / Cube Strength: 12 / 15 MPa; Common UK Name: GEN 1; Typical Use: Trench fill, oversite, bedding and domestic mass concrete; Specifier Note: Light duty
• Grade: C16/20; Cylinder / Cube Strength: 16 / 20 MPa; Common UK Name: GEN 2 / ST2; Typical Use: Shed bases, drainage works, light strip footings; Specifier Note: Domestic
• Grade: C20/25; Cylinder / Cube Strength: 20 / 25 MPa; Common UK Name: GEN 3 / ST4; Typical Use: Footpaths, patios, garage bases, internal slabs; Specifier Note: Popular
• Grade: C25/30; Cylinder / Cube Strength: 25 / 30 MPa; Common UK Name: ST5 / RC25; Typical Use: Driveways, garage floors, footings and light reinforcement; Specifier Note: Durability check
• Grade: C30/37; Cylinder / Cube Strength: 30 / 37 MPa; Common UK Name: RC30; Typical Use: Reinforced slabs, beams, columns, agricultural yards; Specifier Note: Engineer spec
• Grade: C35/45; Cylinder / Cube Strength: 35 / 45 MPa; Common UK Name: RC35; Typical Use: Structural reinforced concrete, heavy duty slabs, external exposure; Specifier Note: BS 8500 spec
• Grade: C40/50; Cylinder / Cube Strength: 40 / 50 MPa; Common UK Name: RC40; Typical Use: High strength reinforced concrete, precast, demanding structural work; Specifier Note: Specialist

Concrete Mix Ratios C8/10 to C40/50

Nominal concrete ratios are usually shown ascement : sharp sand : coarse aggregate. They are useful for small DIY jobs because they help you estimate how many cement bags, tonnes of ballast, sand and aggregate may be needed. However, nominal ratios do not fully control water-cement ratio, grading, admixtures, moisture content, cement replacement, compaction or curing. That is why the guide labels these asestimating ratios, not guaranteed structural mix designs.

For domestic work, C20/25 is often treated as a general slab grade and is commonly associated with a 1:2:4 style ratio. C25/30 is stronger and may be used for driveways or footings. C30/37 and above should usually be ordered as ready-mix because the performance depends on controlled batching, measured water, correct cement content and proper quality assurance. If you are working out a retaining wall, beam, reinforced suspended slab or foundation near trees, drains or unstable ground, do not rely on a generic online ratio.

Important Mix Design Limitation

This guide gives practical quantity estimates. It does not replace a BS 8500 mix specification, structural design, exposure class assessment, slump/consistence class, chloride class, aggregate size selection or cube testing. When the work is structural, order certified ready-mix from a supplier and provide the engineer’s concrete specification.

• Grade: C8/10; Indicative Nominal Ratio: 1 : 4 : 8; Cement kg/m³: 170; Water-Cement Guide: 0.70–0.75; DIY Suitability: Blinding only
• Grade: C12/15; Indicative Nominal Ratio: 1 : 3 : 6; Cement kg/m³: 190; Water-Cement Guide: 0.65–0.70; DIY Suitability: Low strength
• Grade: C16/20; Indicative Nominal Ratio: 1 : 2.5 : 5; Cement kg/m³: 220; Water-Cement Guide: 0.60–0.65; DIY Suitability: Small works
• Grade: C20/25; Indicative Nominal Ratio: 1 : 2 : 4; Cement kg/m³: 260; Water-Cement Guide: 0.55–0.60; DIY Suitability: Common DIY
• Grade: C25/30; Indicative Nominal Ratio: 1 : 1.5 : 3; Cement kg/m³: 300; Water-Cement Guide: 0.50–0.55; DIY Suitability: Care needed
• Grade: C30/37; Indicative Nominal Ratio: 1 : 1.25 : 2.5; Cement kg/m³: 330; Water-Cement Guide: 0.45–0.50; DIY Suitability: Ready mix better
• Grade: C35/45; Indicative Nominal Ratio: 1 : 1 : 2; Cement kg/m³: 360; Water-Cement Guide: 0.42–0.48; DIY Suitability: Supplier design
• Grade: C40/50; Indicative Nominal Ratio: Engineered; Cement kg/m³: 390+; Water-Cement Guide: ≤0.45 typical; DIY Suitability: Certified mix

How the Guide Converts Volume Into Materials

The guide first works out wet concrete volume from length × width × depth. It then applies the selected waste allowance. For site-mix estimating, it uses a dry-volume factor to allow for voids between aggregate particles and loss during mixing. Cement is estimated from typical cement content by grade, then sand and aggregate are distributed from the selected nominal ratio. The result is suitable for ordering materials for a small slab or checking whether buying bags makes sense, but it should not be used as the final control method for a structural pour.

• Cement bags:determined as 25 kg bags, with rounding up because cement is bought in full bags.
• Water:estimated using an indicative water-cement ratio, but real water demand depends on aggregate moisture and workability.
• Sand and aggregate:shown as approximate tonnes and loose cubic metres so you can compare bulk bag deliveries.
• Ready mix:costed per cubic metre because UK concrete suppliers normally price delivered concrete by m³.

Ready Mix Concrete Cost UK 2026

In 2026, UK ready-mix concrete pricing is still best treated as a quote-based market. The grade, distance from the batching plant, minimum load size, delivery timing, pump requirement, waiting time, access and regional labour costs all affect the final price. Publicly available trade price guides commonly place basic ready-mix concrete around the£90–£160 per m³range, with stronger or specialist mixes, small-load surcharges and London delivery increasing the total.

For budgeting, this page uses a grade-based base price and then applies a regional multiplier. A C8/10 blinding mix is cheaper than a C40/50 structural mix because stronger concrete normally requires more cement, tighter quality control and often admixtures. The guide also adds optional finish, reinforcement, DPM, testing and access costs so the result is closer to a real job budget rather than a simple material-only number.

Buying Tip for 2026

For pours above about 1.5–2.0 m³, ready mix is usually more consistent and less labour intensive than hand mixing. For very small jobs, bagged concrete or ballast plus cement can be cheaper, but only if you can mix, place, compact and finish the concrete before it begins to stiffen.

• Concrete Grade: C8/10; Indicative 2026 Supply Cost / m³: £90–£105; Typical Job: Blinding / lean fill; Cost Note: Low cement
• Concrete Grade: C12/15; Indicative 2026 Supply Cost / m³: £95–£110; Typical Job: Mass fill / oversite; Cost Note: Basic
• Concrete Grade: C16/20; Indicative 2026 Supply Cost / m³: £100–£120; Typical Job: Light domestic work; Cost Note: Common
• Concrete Grade: C20/25; Indicative 2026 Supply Cost / m³: £105–£130; Typical Job: Slabs / footpaths; Cost Note: Popular
• Concrete Grade: C25/30; Indicative 2026 Supply Cost / m³: £115–£140; Typical Job: Driveways / footings; Cost Note: More cement
• Concrete Grade: C30/37; Indicative 2026 Supply Cost / m³: £125–£150; Typical Job: Reinforced concrete; Cost Note: Specify carefully
• Concrete Grade: C35/45; Indicative 2026 Supply Cost / m³: £135–£165; Typical Job: Structural RC; Cost Note: Engineer spec
• Concrete Grade: C40/50; Indicative 2026 Supply Cost / m³: £145–£180+; Typical Job: High strength RC; Cost Note: Specialist

What Changes the Final Concrete Price?

• Small loads:many suppliers add a short-load charge because the delivery cost is similar even if you only need 1m³.
• Concrete pump:required where a mixer cannot discharge near the pour; budget several hundred pounds for small domestic pumps.
• Waiting time:if site labour is not ready, the supplier may charge for waiting beyond the included unloading time.
• Finish:power floating, steel trowel finish, brush finish and tamp finish all have different labour requirements.
• Weather:cold weather, hot weather or heavy rain may require admixtures, protection, curing blankets or a postponed pour.
• Testing:structural or commercial projects may require cube testing and documentation as part of quality control.

Price Guide Sources to Compare

Because concrete prices move with cement, aggregate, haulage and fuel costs, always compare this guide with live supplier quotes. For extra market context, check public UK cost guides such asCheckatrade’s ready-mix concrete cost guideandMyJobQuote’s 2026 concrete pouring cost guide. Use those as broad benchmarks only, then request a written quote for your exact postcode, grade, volume, unloading method and delivery date.

How to Specify Concrete Correctly Under BS 8500

The phrase “I need C25 concrete” is often not enough for a supplier or building control officer. In a proper UK concrete specification, the strength class is only one part of the order. A full specification may include strength class, designated concrete type, exposure class, consistence/slump class, maximum aggregate size, chloride class, cement or combination type, minimum cement content, maximum water-cement ratio, reinforcement cover and any special requirements such as air entrainment, waterproofing admixture or sulphate resistance.

For many domestic projects, a ready-mix supplier can help you choose a standard designated concrete if you explain the use clearly. For example, a garden shed base is not the same as a reinforced driveway, and a driveway exposed to de-icing salts is not the same as an internal garage slab. Where there is reinforcement, structural load, frost exposure, aggressive ground, retaining height or building-control involvement, the design should be checked before ordering.

Strength Class

The C-grade, such as C20/25 or C30/37, states characteristic compressive strength at 28 days using cylinder/cube notation.

Exposure Class

Exposure class reflects frost, carbonation, chloride, sulphate, wet/dry cycling and ground conditions that affect durability.

Consistence / Slump

Slump or consistence class controls workability. Too wet a mix may be easy to place but can reduce strength and durability.

Structural Warning

Do not use online guides to downgrade a concrete grade on structural work. If the drawings call for C30/37, RC35, a specific exposure class, sulphate-resisting cement, air entrainment or cube testing, order exactly what is specified. Substituting a weaker nominal mix can lead to cracking, poor durability, failed inspection and expensive removal.

Common UK Concrete Ordering Checklist

• Confirm project type: slab, footing, trench fill, driveway, garage floor, retaining wall, beam, column or reinforced base.
• Confirm dimensions and volume, then add a realistic 5–10% over-order allowance.
• Ask whether access needs a pump, wheelbarrow run, line pump, boom pump or mixer discharge direct to shuttering.
• Confirm concrete grade, exposure class, consistence/slump class and maximum aggregate size where required.
• Confirm whether mesh reinforcement, fibres, DPM, expansion joints, curing membrane or power floating are required.
• Book labour, resources and finishing equipment before the truck arrives; concrete wait-time is expensive and concrete cannot be paused.
• Plan curing for at least the first few days. Concrete gains strength by hydration and should not dry out too quickly.

Which Concrete Grade Should You Choose by Project Type?

Choosing concrete by grade is not just about selecting the highest number. A stronger mix normally costs more, may be less forgiving to place, and still fails if it is poured on a poor sub-base or allowed to dry out too quickly. A lower grade can be perfectly suitable for blinding or mass fill but completely unsuitable for a driveway, garage slab or reinforced element. The most economical specification is the one that matches the load, exposure, depth, reinforcement and finish requirement.

For small domestic projects, many builders use familiar rules of thumb: C16/20 for light bases, C20/25 for general slabs, and C25/30 for driveways or garage floors. These can be reasonable starting points, but they do not replace site judgement. Ground conditions, trees, drainage, frost, sulphates, nearby foundations and vehicle loading all matter. A 100mm shed base on well-compacted MOT Type 1 is a different risk from a 150mm driveway slab where cars turn, brake and park every day.

Shed Base / Garden Room

C16/20 or C20/25 may be suitable for light loads, but thicker sections and reinforcement are common for heavy garden rooms, workshops and hot tubs.

Driveway / Parking Bay

C25/30 is a common budget grade, with air entrainment or durability upgrades considered where frost, salts and regular vehicle loads are expected.

Reinforced Foundation

C30/37 or engineer-specified RC mixes should be ordered as certified ready-mix, especially where building control evidence is required.

• Project: Blinding layer; Typical Starting Grade: C8/10; Typical Depth: 25–75mm; Key Specification Check: Clean working surface; Notes: Not loadbearing
• Project: Shed base; Typical Starting Grade: C16/20 to C20/25; Typical Depth: 100–150mm; Key Specification Check: Sub-base and level; Notes: Domestic
• Project: Patio slab under paving; Typical Starting Grade: C20/25; Typical Depth: 100–150mm; Key Specification Check: Falls and drainage; Notes: Common
• Project: Driveway slab; Typical Starting Grade: C25/30; Typical Depth: 125–175mm; Key Specification Check: Vehicle loading and joints; Notes: Durability
• Project: Garage floor; Typical Starting Grade: C25/30 to C30/37; Typical Depth: 150mm+; Key Specification Check: DPM, insulation and finish; Notes: Finish critical
• Project: Strip footing; Typical Starting Grade: C20/25 to C25/30; Typical Depth: Engineer / building control; Key Specification Check: Ground bearing and depth; Notes: Check drawings
• Project: Retaining wall base; Typical Starting Grade: C30/37+; Typical Depth: Engineer design; Key Specification Check: Rebar, cover and drainage; Notes: Do not guess

Concrete Thickness Is as Important as Grade

A common budgeting mistake is to focus on concrete grade while ignoring thickness. A stronger 75mm slab on a weak sub-base is often worse than a correctly placed 150mm slab on compacted hardcore. For a footpath or light shed base, 100mm may be enough in many domestic settings. For vehicle areas, garage slabs, workshops and hot tub bases, 125–150mm or more is common, often with mesh reinforcement and properly planned movement joints. For foundations, retaining structures and structural slabs, thickness must follow drawings, ground conditions and engineering design.

Sub-base quality also matters. Concrete is strong in compression but poor in tension; voids, soft spots and settlement below the slab create bending and cracking. Before ordering concrete, excavate organic material, compact the formation, install a suitable granular sub-base, set shuttering accurately, plan falls where water must drain away, and make sure reinforcement is chaired at the correct height rather than lying on the ground.

Concrete Curing, Slump and Strength Gain in 2026 Projects

Concrete does not “dry” into strength in the same way paint dries. It hardens through hydration, a chemical reaction between cement and water. If the surface loses moisture too quickly in sun, wind or low humidity, the concrete may shrink, dust, crack or fail to reach its intended durability. Good curing is one of the cheapest ways to protect a slab, yet it is one of the most commonly skipped steps on small domestic projects.

Most concrete strength classes are referenced at 28 days, but the slab will gain usable early strength sooner. Many domestic slabs can be walked on after one to two days depending on weather, mix and finish, while vehicle loading should usually wait longer. Cold weather slows strength gain, and freezing fresh concrete can seriously damage it. In hot weather, concrete may set quickly, making finishing more difficult and increasing the risk of plastic shrinkage cracking.

Do Not Over-Water

Adding extra water on site may improve workability for a few minutes, but it can reduce strength, increase shrinkage and weaken the surface.

Cure the Surface

Use curing membrane, polythene sheets or controlled damp curing to reduce early moisture loss, especially in warm or windy weather.

Protect From Frost

Avoid pouring onto frozen ground and protect fresh concrete in cold weather with insulated blankets or supplier-approved winter measures.

Slump and Workability Explained

Slump describes how workable the fresh concrete is. A higher slump can make concrete easier to place in congested reinforcement or awkward shuttering, but it should be achieved by proper mix design or admixtures, not by adding uncontrolled water on site. If you need very workable concrete, tell the ready-mix supplier about the placement method. Pumped concrete, trench fill, flat slabs, power-floated floors and heavily reinforced sections all need different workability decisions.

For DIY mixing, the best practical rule is to add water gradually and stop when the mix is workable but not runny. It should consolidate without leaving dry pockets, but it should not bleed excessively or slump like soup. If you can squeeze water from the surface or the aggregate separates from the paste, the mix is likely too wet. If the mix is harsh and unworkable, it may need better aggregate grading, plasticiser or a different approach rather than simply more water.

Do Not Ignore Joints

Large slabs need movement or control joints to manage shrinkage cracking. Joints should be planned before the pour, not cut randomly after cracks appear. For driveways, garage floors and external slabs, joint spacing, saw-cut timing and edge restraint are just as important as the grade of concrete selected.

Common Concrete Mix Design Mistakes to Avoid

A concrete guide can give a good estimate, but site mistakes still cause most failures. The most common problems are ordering too little concrete, choosing the wrong grade, pouring on an unprepared base, adding extra water, failing to compact the concrete, skipping curing and loading the slab too soon. These mistakes are especially costly because failed concrete usually has to be broken out and replaced rather than repaired invisibly.

Another common issue is comparing quotes that are not like-for-like. One supplier may quote C25/30 delivered to kerbside only, while another includes a pump, fibres, finish labour and waiting time. One contractor may include excavation and sub-base, while another only prices concrete placement. Always check what is included: grade, volume, waste, delivery, access, pump, labour, DPM, reinforcement, joints, finish, curing and disposal.

• Ordering exact volume only:small errors in depth or shuttering can leave you short; add a controlled waste allowance.
• Using weak concrete for driveways:traffic loads, braking and frost exposure can damage under-specified slabs.
• Letting mesh sit on the ground:reinforcement must be supported within the slab to work properly.
• Pouring on mud or soft ground:concrete needs a stable, compacted base with drainage considered.
• Adding water at the truck:uncontrolled water can reduce strength and increase shrinkage cracking.
• No curing plan:early drying can ruin the surface even when the concrete grade is correct.

Use This Guide for Estimating — Not Final Structural Approval

This resource helps estimate concrete volume, site-mix materials and 2026 UK budget cost. For structural, reinforced or building-control work, confirm the concrete specification with a competent designer, engineer or ready-mix supplier using BS EN 206 and BS 8500 terminology.

Concrete Mix Design Guide — Frequently Asked Questions

Common questions about concrete grades, C8/10 to C40/50 strength classes, mix ratios, volume, cost and UK specification rules.

The C-grade format shows two characteristic compressive strength values. The first number is the cylinder strength and the second is the cube strength, normally assessed at 28 days. C8/10 is a very low strength concrete usually used for blinding or backing. C40/50 is a high-strength concrete used for demanding reinforced or specialist work. In the UK, concrete specification is normally linked to BS EN 206 and BS 8500, so the grade should be considered alongside exposure class, consistency, aggregate size and durability requirements.

For many simple domestic slabs, paths, shed bases and patios, C20/25 is a common starting point. For a driveway, garage floor or slab carrying heavier loads, C25/30 or C30/37 may be more suitable. The right answer depends on loading, thickness, sub-base, reinforcement, exposure to frost or de-icing salts, and whether building control or an engineer is involved. Always follow project drawings and supplier guidance where provided.

It is not recommended to hand mix C30/37 or C40/50 for structural work. Higher strength concrete requires tighter control of cement content, water-cement ratio, aggregate grading, admixtures, mixing time, compaction and curing. Small errors in water or batching can significantly reduce strength. Order certified ready-mix for high-strength, reinforced or engineered concrete and ask for delivery documentation where compliance evidence is needed.

Multiply length × width × depth in metres to work out volume. For example, a 5m × 4m slab at 150mm thick is 5 × 4 × 0.15 = 3.0m³. Add a waste allowance, usually 5% for accurate shuttering and up to 10–15% for uneven ground, difficult access or trench work. Running short during a pour is expensive because a second delivery may create a cold joint and a small-load surcharge.

A common site-mix estimate for C20/25 is around 1:2:4 — one part cement, two parts sharp sand and four parts coarse aggregate. This is suitable as a rough domestic estimating rule, not a guaranteed certified mix. If the concrete is structural, reinforced, exposed to aggressive conditions or part of a building-control submission, specify ready-mix by strength class and durability requirements rather than relying on a nominal volume ratio.

Typical UK ready-mix concrete budget rates in 2026 often sit around £90–£160 per m³ for common grades, before extras. C8/10 and C12/15 are usually cheaper, while C30/37, C35/45 and C40/50 cost more. The final invoice can also include short-load charges, waiting time, pump hire, weekend delivery, London or South East uplifts, fibres, admixtures, cube testing and finish labour.

GEN mixes are general-purpose concretes used for non-reinforced domestic and low-risk work, ST mixes are standard mixes often used for domestic slabs and footings, and RC mixes are reinforced concrete grades suitable where reinforcement or structural performance is required. The terms are convenient for ordering, but the exact specification should still match the project requirements, particularly where exposure class and durability matter.

Not every slab needs mesh reinforcement, but reinforcement is common in garage floors, driveways, workshops, extensions and slabs that may crack due to loading, shrinkage or ground movement. Mesh does not magically make a weak sub-base acceptable; it should be combined with proper excavation, compacted sub-base, DPM where needed, correct depth, control joints and good curing. For structural slabs, reinforcement must be designed, positioned and supported correctly.

Related UK Construction Guides

Useful guides and guides to continue planning your build, slab, foundation or home improvement project.

For related concrete mix design and proportion working, see MixDesignCalc.xyz.