A concrete driveway should be 100 to 125mm (4 to 5 inches) thick for cars, and 150mm (6 inches) for vans, trucks or regular heavy deliveries. Underneath it wants at least 150mm of well-compacted sub-base.
Those numbers are the easy part. What actually decides whether a driveway lasts is the ground under it and the detail at its edges — both of which get less attention than the slab thickness people obsess over.
Thickness by use
| Use | Slab | Sub-base | Reinforcement |
|---|---|---|---|
| Foot traffic, bins only | 75–100mm | 100mm | Optional |
| One or two cars | 100–125mm | 150mm | A142 mesh |
| Cars plus occasional van | 125–150mm | 150mm | A142 mesh |
| Regular vans, small truck | 150–175mm | 200mm | A193 mesh |
| Caravan or motorhome | 150mm | 200mm | A193 mesh |
| Heavy commercial | 200mm+ | 250mm | Engineer designed |
The step from 100mm to 150mm adds 50% to the concrete cost. On a typical 30m² driveway that’s roughly £180 to £250 of extra concrete — meaningful, but small against the total job, and the right call if anything heavier than a car will ever use it.
Think about delivery vehicles when you decide. A driveway sized for two hatchbacks will still get a skip lorry, a removal van and an oil delivery at some point in its life.
Why the sub-base matters more
Concrete is strong in compression and weak in bending. On uniform, firm support a slab is loaded in pure compression and handles far more than you’d expect. Spanning a soft spot, it bends — and it cracks at a fraction of the load.
A 100mm slab on 150mm of properly compacted MOT Type 1 will outperform a 150mm slab on 75mm of loose hardcore, every time. If the budget forces a choice, spend it below ground.
Compact in layers of no more than 75mm, four to six passes each with a plate compactor. The finished surface should show no give at all underfoot. There’s more in our guide to sub-base depth and compaction.
Edges fail before the middle
This is the detail that separates driveways that last from driveways that don’t.
In the middle of a slab, load is supported by ground on all sides. At an edge, there’s ground on one side only, so the same wheel load produces roughly twice the bending stress. And the edge is exactly where car wheels sit when someone parks slightly wide.
The fix is a thickened edge: increase the slab depth to 200 to 250mm over the outer 300mm, tapering back to the standard thickness. On a 30m² driveway it costs about 0.3m³ of extra concrete — around £35 — and it addresses the single most common failure point.
Alternatively, form a concrete or block edging that confines the slab and takes the wheel load off the free edge.
Concrete volume by driveway size
| Driveway | Area | At 100mm | At 125mm | At 150mm |
|---|---|---|---|---|
| Single, 3 × 6 m | 18 m² | 1.8 m³ | 2.3 m³ | 2.7 m³ |
| Single, long 3 × 10 m | 30 m² | 3.0 m³ | 3.8 m³ | 4.5 m³ |
| Double, 5 × 6 m | 30 m² | 3.0 m³ | 3.8 m³ | 4.5 m³ |
| Double, 5 × 10 m | 50 m² | 5.0 m³ | 6.3 m³ | 7.5 m³ |
| Large, 6 × 12 m | 72 m² | 7.2 m³ | 9.0 m³ | 10.8 m³ |
Add roughly 8% for wastage, plus the thickened edge. Note how quickly the volume crosses the part-load threshold — a double driveway at 125mm is comfortably a full load, which means the best price per cubic metre you will get.
Reinforcement
A142 mesh is the domestic standard, positioned in the middle third of the slab depth on chairs. It doesn’t stop cracking — it holds cracks tight so they stay hairline rather than opening up and letting water in.
Mesh lying on the sub-base does nothing at all. It has to be in the concrete, not under it, and it’s the most common mistake on DIY driveways.
Polypropylene fibres mixed into the concrete are an alternative for controlling early shrinkage cracking, but they don’t replace mesh for load distribution. On a driveway carrying vehicles, use mesh — or both.
Concrete strength
C25 minimum, C30 preferred. In frost-prone areas specify air entrainment, and if you’ll ever use de-icing salt treat it as essential — salt scaling ruins driveway surfaces faster than anything else.
The price step from C25 to C30 is around £8 per cubic metre, roughly £30 on a typical driveway. There’s no sensible argument for saving it.
Where thickness will not save you
Three failure modes are unaffected by how thick the slab is, and all three are more common than crushing.
Settlement. If the ground beneath moves, the slab moves with it. A thicker slab bridges a small void slightly better but cannot span a failed sub-base.
Surface scaling. Frost and de-icing salt attack the top few millimetres. A 200mm slab with a poorly cured surface scales exactly as readily as a 100mm one. Air entrainment and proper curing are the defences, not depth.
Shrinkage cracking. All concrete shrinks as it cures, and thicker slabs actually shrink slightly more in absolute terms. Control joints at the right spacing are what manage it.
Getting the thickness right matters, but it is one of four decisions rather than the only one.
Joints and falls
Control joints every 2.4 to 3m for a 100mm slab, 3.6 to 4.5m at 150mm, cut to a quarter of the slab depth within 24 hours. Keep panels roughly square — long thin panels crack across the middle regardless of joint spacing.
Falls should shed water away from the house at a minimum of 1:80. Where the driveway slopes towards a garage or the property, a channel drain across the entrance is a requirement rather than an option in most jurisdictions.
Drainage reduces heave
Frost heave needs three things together: freezing temperatures, frost-susceptible soil, and water. Remove any one and the problem largely disappears.
You cannot change the climate or easily change the soil, but you can control water. Free-draining granular backfill against a foundation, a perimeter drain at footing level, and surface falls that carry water away from the building all reduce heave substantially — often more cheaply than digging deeper.
Working out the concrete
Volume is area × thickness, plus the thickened edge. A 10m × 3m driveway at 125mm is 30 × 0.125 = 3.75 m³, and the thickened edge adds roughly another 0.3m³. Add 8% for wastage and you’re ordering about 4.4m³.
Use the slab calculator for your dimensions, then price it with the cost calculator before committing to a thickness.
Common questions
Is 100mm thick enough for a driveway?
For ordinary cars on a well-compacted 150mm sub-base with mesh and thickened edges, yes. If a van, caravan or regular deliveries are likely, go to 150mm.
What is the minimum sub-base for a driveway?
150mm of compacted MOT Type 1 or crushed stone, laid and compacted in two layers. More on clay or soft ground.
Do I need mesh in a concrete driveway?
Yes. A142 is the domestic standard, held in the middle third of the slab on chairs. It controls crack width under the concentrated loads that wheels apply.
How long before I can drive on a new driveway?
Seven days for a car as a minimum, ten to fourteen is safer. Wait the full 28 days for anything heavy. Cold weather extends all of these.
Why has my driveway cracked at the edges?
Almost always a thin edge with no thickening, wheels parking on it, and possibly a sub-base that stops short of the slab edge. The sub-base should extend at least 150mm beyond the concrete on all sides.