How Much Does a Concrete Slab Cost in 2026?
A concrete slab costs £50–£80 per m² installed, depending on thickness and what it is for. A small shed base starts at around £300, a standard garage base runs £1,200–£2,000, and a structural extension raft foundation can reach £2,500–£5,000. Here is the full cost breakdown — including thickness guidance, DIY tips, and where you can realistically save money.
From £300
Shed base (2×2m)
£1,200–£2,000
Garage base (3×6m)
£50–£80
Per m² installed
100–150mm
Thickness range
Prices updated April 2026 · Based on industry data and contractor submissions.
Quick guide. Use 100mm for shed bases, 150mm for garage floors and driveways, and 150–200mm for extension raft foundations. Always lay on a compacted MOT Type 1 sub-base with a damp proof membrane underneath.
Concrete Slab Cost by Type
All prices below are for the full job — groundwork preparation, formwork, membrane, mesh reinforcement, concrete pour, and a standard finish. They do not include structural engineer fees or Building Regulations applications, which are required for extension foundations.
Shed base (2×2m, 100mm thick)
Small garden building base, basic prep included
£400
£300 – £500
Hot tub base (2.5×2.5m, 150mm thick)
Reinforced slab to handle hot tub weight
£550
£400 – £700
Garage base (3×6m, 150mm thick)
Standard single garage, mesh reinforcement
£1,600
£1,200 – £2,000
Driveway slab (30m², 150mm thick)
Brushed or trowelled finish, vehicle-rated
£3,000
£2,000 – £4,000
Extension raft foundation (30m²)
Structural slab, engineer-specified, Building Regs
£3,750
£2,500 – £5,000
Concrete per m³ delivered (ready-mix)
Supply-only price for ready-mix lorry delivery
£100/m³
£80 – £120/m³
What Affects the Cost of a Concrete Slab?
Several things determine what you will end up paying. Some you can control; others are fixed by your site and the job at hand.
Size of the slab
Bigger slabs cost more in total but the per-m² price generally falls as the job gets larger. A 2×2m shed base works out at a higher cost per square metre than a 6×10m garage base, because the fixed costs (groundwork, formwork, minimum concrete loads) are spread over a larger area.
Thickness and reinforcement
A 100mm plain slab is cheaper than a 150mm reinforced one. Structural raft foundations — which need engineer-specified rebar, thickened edges, and Building Control sign-off — are significantly more expensive per m² than a basic shed base. A142 or A193 mesh adds around £5–£10 per m² to the materials cost.
Ground conditions and preparation
If the ground is soft, waterlogged, or has tree roots, more excavation and sub-base preparation is needed. A standard job involves digging out 150–200mm, compacting a Type 1 MOT sub-base, and laying a damp proof membrane. Poor ground can add £500–£1,500 to the preparation costs alone.
Access for the concrete truck
Ready-mix lorries are large. If one cannot get close enough to pour directly into the formwork, you will need a concrete pump (£200–£400 per half day) or extra labourers to barrow the concrete in quickly before it sets. Rear-garden jobs almost always need a pump or wheelbarrow relay team.
Finish
A basic tamped or power-floated finish is standard and the most affordable. A brushed finish for driveways costs slightly more. Exposed aggregate, pattern-imprinted concrete, or polished finishes all add cost — sometimes doubling the labour element. For a plain shed base, finish quality matters very little.
Waste removal
Excavating a 3×6m garage base at 200mm depth produces around 3.5 tonnes of spoil. A skip to remove it costs £200–£350 on top of the slab price. Some groundworkers include skip hire in their quote; others do not, so always check what is included.
Ready-Mix vs Site-Mixed Concrete
For anything over about 1m³ of concrete, ready-mix delivered by lorry is the sensible choice. Here is how the two options compare.
Ready-mix (lorry delivered)
- Standard for garage bases, driveways, and extensions
- Consistent mix quality every time
- Minimum load is typically 3–6m³ (or a minimum charge of £150–£250)
- Best for anything over 1m³
- Mini-mix (volumetric) trucks solve the minimum load problem for smaller jobs (£100–£160/m³)
Site-mixed concrete
- Only practical for very small jobs under 0.5m³
- Bagged concrete from B&Q or Wickes works out at ~£200 per m³
- Labour-intensive — mixing by hand or with a small mixer
- Good for repairs, small pads, and post bases
- Not suitable for anything structural
Concrete Slab Thickness Guide
Getting the thickness right is important — too thin and the slab will crack; thicker than necessary just wastes money. Here is what is recommended for each common use.
| Use | Thickness | Grade |
|---|---|---|
| Garden path | 75mm | C20 |
| Shed / summerhouse base | 100mm | C25 |
| Patio base | 100mm | C20 |
| Hot tub base | 150mm | C25 |
| Garage floor | 150mm | C25 |
| Driveway | 150mm | C30 |
| Extension raft foundation | 150–200mm | C30+ |
Reinforcement: Mesh or Rebar?
A142 mesh
6mm steel bars at 200mm centres. Standard for shed bases, patio bases, and light-duty slabs. Costs around £8–£12 per sheet (2.4m × 4.8m). Placed on small plastic chairs to keep it in the middle of the slab thickness, not resting on the ground.
A193 mesh
7mm bars at 200mm centres — slightly heavier. Used for garage floors, driveways, and any slab taking vehicle loads. Adds around £3–£5 per m² to the materials cost compared to A142.
Rebar (reinforcing bar)
Specified by a structural engineer for load-bearing foundations — raft slabs, strip foundations, and ground-floor slabs for extensions. Rebar is tied into cages and placed precisely to the engineer's drawing. Never substitute mesh for rebar in structural applications without engineer sign-off.
Fibre reinforcement
Polypropylene fibres mixed into the concrete before pouring. Reduces plastic shrinkage cracking during curing and is sometimes used in addition to (not instead of) mesh on larger domestic slabs. Adds £20–£40 to the concrete cost per m³.
Ground Preparation
A good concrete slab needs a good base. Skipping proper preparation is the most common reason slabs crack, sink, or move. These are the standard steps:
- 1
Dig out
Remove topsoil and any soft ground to a depth of 150–200mm below your finished slab level. Topsoil compresses and rots; the slab must sit on solid, stable ground.
- 2
Compact the sub-base
Lay 100–150mm of MOT Type 1 hardcore (crushed stone) and compact it thoroughly with a plate compactor. This creates a stable, load-spreading base and helps with drainage.
- 3
Damp proof membrane (DPM)
Lay a 1200-gauge polythene sheet over the sub-base. This stops ground moisture wicking up through the slab. Overlap joins by 300mm and lap up the inside of the formwork.
- 4
Timber formwork
Nail or stake treated timber boards around the perimeter to contain the concrete. Check for level and make sure everything is square before the concrete arrives.
- 5
Reinforcement
Place your A142 or A193 mesh on plastic spacers (chairs) so it sits in the middle of the slab depth. For structural slabs, follow the engineer's reinforcement drawing exactly.
Can I Lay a Concrete Slab Myself?
For a small shed base — say 2×2m or under — a competent DIYer can handle the whole job over a weekend. The key things to know:
Keep it small
Anything under 4m² is manageable for one person with some concrete experience. Above that, you need at least two people — one pouring and barrowing, one screeding and levelling — because the concrete starts to go off quickly.
Use a mini-mix supplier
Rather than bags from a builders' merchant, call a volumetric (mini-mix) concrete supplier. They mix the exact amount you need on site. No minimum load, no wastage, and far less work than mixing bags by hand.
Have everything ready before pouring
Once the concrete is in the barrow, you have 30–45 minutes to place and screed it properly. Formwork, mesh, and tools must all be in place before the truck arrives. Rushing this stage is how you end up with an uneven or cracked slab.
Leave it to cure properly
Cover the fresh slab with polythene in hot or windy weather to stop it drying too fast. Do not load it for at least 48 hours, and leave a shed base a week before placing the building on it.
How to Get Your Concrete Slab for Less
Get at least three quotes
Groundwork prices can vary by 30–40% between local contractors. Always get at least three written quotes for a concrete slab — one from a specialist groundworker, one from a general builder, and one from a driveway/landscaping company if relevant. Make sure each quote includes the same scope: excavation, sub-base, membrane, mesh, pour, and finish.
Combine groundworks wherever possible
If you are having a driveway and a shed base done, book them together. Groundworkers are significantly cheaper when you give them a bigger job — the mobilisation costs (machine hire, waste removal, concrete delivery) are shared across both jobs. You might save 15–20% compared to booking them separately.
DIY shed bases under 4m²
For a small shed base, a confident DIYer can handle the whole job. Dig out 150mm, compact a 50mm layer of MOT Type 1 hardcore, lay a damp proof membrane, build simple timber shuttering, then order concrete from a mini-mix supplier (no minimum load issues). The concrete will cost around £150–£200 for a 2×2m base; the labour saving is around £200–£300.
Book for autumn or early winter
Spring and summer are peak season for groundworkers, and prices reflect it. Booking your concrete slab for September through November can save 10–15%, and contractors are more likely to fit you in quickly. Avoid hard frosts — concrete needs to stay above 5°C as it cures — but mild autumn weather is perfectly fine for outdoor groundwork.
Useful Resources
What to Expect: The Concrete Slab Laying Process
Laying a concrete slab typically takes 1-2 days depending on the size, plus curing time. Here's what the groundworker will do at each stage.
- 1
Mark out and excavate
The slab area is marked with string lines and pegs. The ground is excavated to the required depth, typically 200-300mm depending on the slab thickness and what it will support. Topsoil and soft material are removed.
- 2
Lay the sub-base
A layer of MOT Type 1 compacted hardcore (usually 100-150mm) is spread and levelled. This provides a stable, well-drained foundation and prevents the slab from cracking due to ground movement.
- 3
Install formwork and membrane
Timber shuttering is erected around the perimeter to contain the concrete at the correct level. A damp-proof membrane (DPM) is laid over the sub-base if the slab will support a habitable structure such as a garage or extension.
- 4
Add reinforcement
Steel mesh (A142 or A193) is placed on spacers within the formwork to sit in the lower third of the slab. Reinforcement prevents cracking and is essential for driveways, garages, and any slab carrying structural loads.
- 5
Pour and level the concrete
Ready-mixed concrete (typically C25 or C30 grade) is delivered and poured into the formwork, spread with rakes, and levelled using a screed board or tamping beam. A power float gives a smooth finish.
- 6
Curing
The slab is covered with polythene sheeting or damp hessian to retain moisture. It should be left for at least 48 hours before foot traffic, and 7 days before any heavy loads are placed on it. Proper curing prevents surface cracking.
Frequently Asked Questions
How much does a concrete slab cost per m²?
A fully installed concrete slab costs £50–£80 per square metre for a standard domestic base, including groundwork preparation, formwork, reinforcement mesh, pour, and levelling. That works out to around £300–£500 for a small shed base and £1,200–£2,000 for a standard single-garage base. Extension raft foundations cost more — typically £2,500–£5,000 — because of the additional structural design, thicker pour, and reinforcement required.
How thick should a concrete slab be?
The right thickness depends on what the slab is for. A 75mm slab is fine for garden paths. A 100mm slab suits shed and garden structure bases. Garage floors and driveways need at least 150mm to handle vehicle weight. Extension raft foundations typically require 150–200mm, often with thickened edges and structural reinforcement — always follow engineer or Building Control guidance for these.
Do I need reinforcement in a concrete slab?
Most domestic slabs benefit from reinforcement mesh to reduce cracking. A142 mesh (6mm bars at 200mm centres) suits shed and patio bases. A193 mesh (7mm bars) is better for garage floors and driveways. Structural slabs — such as extension raft foundations — require engineer-specified rebar, not just mesh. For anything load-bearing, always get a structural engineer involved.
Can I lay a concrete slab myself?
A small shed base (up to around 4m²) is within the reach of a competent DIYer. You will need to dig out and compact a sub-base, lay a damp proof membrane, build timber formwork, mix or order concrete, pour and level it, then leave it to cure for at least 24–48 hours before any light use. Anything larger really needs a team: the concrete goes off quickly and you need multiple people to screed and level it before it sets.
What is the difference between a concrete slab and a raft foundation?
A basic concrete slab (like a shed or garage base) sits on a prepared sub-base and is not structural — it simply provides a level, stable surface. A raft foundation is a structural slab that spreads the load of a building across the ground, used for extensions, outbuildings, and new builds. Raft foundations require engineer design, Building Regulations approval, and are significantly thicker and more heavily reinforced than a domestic base slab.
How long does a concrete slab take to cure?
Concrete reaches initial set within a few hours and is safe to walk on after around 24–48 hours. However, it takes approximately 28 days to reach full strength. For a shed base, you can place the shed after a few days of dry weather. For a garage base or extension foundation, allow the full curing period before applying loads. Avoid pouring in freezing temperatures — concrete needs to stay above 5°C to cure properly.
Written by Chris Ward, Less.co.uk founder
Last updated: April 2026 · Pricing based on industry data and verified contractor submissions · Methodology
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Building Regulations
Concrete slabs used as structural extension foundations must comply with Approved Document A (Structure) and require Building Control approval before work starts. Basic shed and garage bases do not normally need Building Regulations approval, but always check with your local authority if you are unsure.
