Quick answer: A residential concrete driveway should generally be 100mm thick with steel mesh reinforcement. Driveways carrying trucks, caravans or machinery should be 125–150mm with heavier reinforcement. The right thickness depends on the soil and the loads, so it should be set to the engineering for your site.
Recommended driveway thickness
| Use | Thickness | Reinforcement |
|---|---|---|
| Cars & light vehicles | 100mm | Steel mesh (e.g. SL72) |
| Caravans / boats / 4WDs | 100–125mm | Heavier mesh |
| Trucks / machinery | 125–150mm+ | Engineered to spec |
Why reactive soil matters
Much of the Adelaide Hills and Mid North has reactive clay that swells and shrinks with moisture. That movement is a leading cause of cracking, so correct thickness, reinforcement and control joints are essential here.
Steep driveways
On steep blocks, the surface needs grip — a broom finish or, better, exposed aggregate. Get the fall and jointing right and consider the turning and transition grades so vehicles don't scrape.
Drainage
- Fall the driveway so water runs away from the house and garage.
- Add a grated drain across the base of steep driveways.
- Keep water off the slab edges to protect the base.
We design all of this into every driveway we pour, especially across the Adelaide Hills.
Common slope and drainage mistakes
- Not enough fall — a driveway needs a minimum grade (around 1 in 100) to shed water. We set the fall at pour time; it can't be fixed afterwards.
- Falling toward the house — a frequent error that sends water at the garage and footings. The slab must drain away from buildings.
- Blocked or missing drains — steep driveways often need a grated drain at the base, kept clear of leaves and silt.
- Unprotected edges — water running off the slab edge erodes the base; an edge strip or path helps.
Reactive soil and control joints
Much of the Adelaide Hills, Mount Barker and the Mid North sits on reactive clay that swells and shrinks with moisture. That movement is the biggest threat to a driveway, and the defence is correct reinforcement plus control joints cut at sensible spacing so the concrete cracks along the joint lines rather than randomly across the surface. Control joints are cheap insurance; uncontrolled cracking is not.
Curing in the Adelaide climate
In a hot, dry Adelaide summer, concrete can lose surface moisture too quickly, which weakens the top layer and invites crazing. We cure slabs properly — protecting them through the critical early days — because how a slab is cured in its first weeks largely decides how it performs for the next thirty years. Get the thickness, reinforcement, base, drainage and curing right, and a driveway will stay sound and flat for decades; cut corners on any of them and problems show up within a few years.
Reinforcement: mesh, bar and where it sits
Reinforcement does not stop concrete from cracking — it holds any cracks tightly closed so they stay fine and don't widen or step. For that to work, the steel has to sit in the correct part of the slab, chaired up off the base rather than lying on the ground where it does nothing. Standard residential driveways use steel mesh; heavier-duty driveways carrying trucks or machinery, and slabs on very reactive ground, use heavier mesh or bar to an engineer's detail. We set the reinforcement properly every time, because it is invisible once the concrete is poured and impossible to fix later.
How thickness ties in with the base
Thickness only delivers if the base beneath it is right. A 100mm slab on a well-compacted crushed-rock base will outperform a thicker slab poured on soft, uneven or poorly drained ground. That's why we treat the base preparation — and, where needed, the earthworks — as part of the same job as the pour.
More questions about thickness, slope and drainage
How thick for a normal driveway? Generally 100mm with mesh; thicker for heavier loads. What fall does a driveway need? Enough to shed water away from buildings — more on a slope. Best finish for a steep, wet driveway? A grippy one — usually exposed aggregate — which is common across the Adelaide Hills.