How Thick Should a Concrete Driveway Be?

Thickness is the single biggest factor in how long a concrete driveway lasts and what it can carry. Pour it too thin and it will crack and fail under loads it was never built for. Pour it too thick and you are spending money on concrete you do not need. Getting it right means matching the slab to how you will actually use it — and on the Fraser Coast, matching it to the ground underneath as well.

This guide explains the standard thicknesses, when to go thicker, why reinforcement matters, and how our local soil and climate factor in. The figures here are a guide; the right specification for your driveway should always come from a concreter who has seen your site.

The standard: 100mm with reinforcing mesh

For a typical residential driveway carrying everyday cars, the benchmark is 100mm (10cm) of concrete reinforced with steel mesh (commonly SL72). This is the minimum we would recommend for a driveway that needs to last.

At 100mm with mesh, a driveway will comfortably handle daily passenger vehicles — cars, SUVs and the occasional light load. For a lot of Hervey Bay and Maryborough homes, this is exactly the right spec.

The mesh is not optional. Concrete is strong under compression but weak under tension, and reinforcement is what holds the slab together when the ground moves or a load flexes it. Skipping the mesh to save a few dollars is a false economy that shows up as cracks within a year or two.

When to go thicker: 125–150mm

Plenty of driveways on the Fraser Coast carry far more than a family car. If any of the following apply to you, you should be looking at a thicker slab:

• Caravans stored or manoeuvred on the driveway
• Boats on trailers — very common around here
• Work utes and trucks loaded with tools and materials
• Trailers carrying machinery, mowers or building materials
• Larger vehicles like motorhomes or dual-cab utes towing

For these uses, 125mm to 150mm with heavier reinforcement is the sensible range. The extra thickness spreads load better and resists the cracking that comes from heavy, concentrated weight — especially the point loads from trailer jockey wheels and stabiliser legs.

Use	Recommended thickness	Reinforcement
Cars, daily passenger vehicles	100mm	Steel mesh (e.g. SL72)
Caravans, boats, light trucks	125mm	Heavier mesh
Trucks, machinery, heavy loads	150mm	Engineered mesh / bars
Crossover (council verge section)	Per council standard	Per council standard

These are indicative. The exact spec — including mesh grade and any extra reinforcement — depends on your loads, the soil and any engineering requirements. The crossover (the section between your boundary and the road) often has its own council standard, which we cover in our guide on council approval for driveways in QLD.

Why reinforcement matters as much as thickness

Two driveways of the same thickness can perform completely differently depending on reinforcement. The steel inside the slab does three jobs:

1. Holds cracks tight. Concrete will get hairline cracks — reinforcement keeps them from opening up and spreading.
2. Distributes load. Steel helps the slab act as one piece rather than independent sections.
3. Resists ground movement. When soil swells and shrinks, reinforcement keeps the slab intact.

For thicker, heavier-duty driveways we may step up from standard mesh to a heavier grade or add reinforcing bars in high-stress areas. The right combination of thickness and steel is what gives a driveway its working life.

The part people forget: the base

Here is the truth that catches a lot of homeowners out — a thick slab on a poorly prepared base will still fail. The ground under your driveway carries the load. If it is soft, uneven or not compacted, the concrete has nothing solid to sit on.

Good base preparation usually means:

• Stripping topsoil and any organic material
• Bringing in and compacting a road base sub-base
• Getting the levels and falls right for drainage
• A consistent, even thickness across the whole slab

On the Fraser Coast this is especially important because of our soils, which brings us to the next point.

Reactive soils on the Fraser Coast

Large parts of the Hervey Bay and Maryborough region sit on reactive clay soils. Reactive soil swells when it gets wet and shrinks when it dries out — and our wet summers followed by dry spells put concrete through exactly that cycle, year after year.

That ground movement is one of the main reasons driveways crack here. It is also why thickness, reinforcement and base prep all have to work together. A properly specified slab on a well-prepared, well-drained base copes with reactive soil far better than a thin, under-reinforced slab thrown onto bare ground.

Drainage is part of the picture too. Keeping water away from under the slab reduces how much the soil moves. We go deeper into the causes in our guide on why concrete driveways crack.

Don’t forget the climate and curing

Thickness and steel get a driveway started, but how it is finished and cured determines whether it reaches its potential. In our hot, breezy climate, concrete can dry too fast and lose strength at the surface if it is not cured properly. A well-cured 100mm slab will outlast a poorly cured 125mm one.

If you are planning a new pour, it is worth understanding the curing timeline too — see our guide on how long before you can drive on new concrete.

What about decorative driveways?

Thickness rules apply regardless of finish. Whether you are pouring plain concrete, exposed aggregate or coloured concrete, the structural slab underneath still needs to be the right thickness and reinforcement for your loads. The decorative finish sits on top of a properly engineered slab — it does not replace the need for one.

If you are weighing up finishes, our comparison of exposed aggregate vs plain concrete and concrete vs pavers for driveways can help you decide.

A quick checklist before you pour

• Cars only? 100mm with mesh is the standard.
• Caravan, boat or truck? Step up to 125–150mm with heavier reinforcement.
• Reactive soil or poor drainage? Make sure base prep and drainage are sorted.
• Crossover section? Check the council standard for the verge.
• Decorative finish? The slab spec stays the same underneath.

Common questions

Is 100mm really enough for a driveway? For everyday cars on a well-prepared base, yes. The problems usually start when a 100mm slab is asked to carry caravans or trucks it was never built for, or when the base prep was skipped.

Can I just go 150mm everywhere to be safe? You can, but for a car-only driveway it is often money better spent elsewhere — like proper base prep and curing. The smarter approach is matching thickness to your actual loads.

How much does thickness add to the cost? More concrete and heavier steel cost more, so a 150mm driveway costs more per square metre than a 100mm one. For ballpark pricing, see our concrete driveway cost guide.

Thickness is an investment, not a cost

It is tempting to view slab thickness purely as a way to save or spend money — and it is true that a thinner slab uses less concrete and steel. But the better way to think about it is as an investment in how long the driveway lasts and what it can do.

A driveway that is correctly specified for its loads will quietly do its job for decades with almost no attention. A driveway that was poured too thin to save a few hundred dollars often starts cracking within a year or two, and once a slab is structurally cracked there is no cheap fix — you are looking at resurfacing or, more often, replacement. We compare those options in our guide on resurface vs replace your driveway.

The smart approach is not “as thin as possible” or “as thick as possible” — it is “exactly right for how you’ll use it.” For a car-only driveway that usually means 100mm with good base prep and curing. For a household that stores a boat and a caravan it means stepping up to suit. Spending the money where it actually does work is what separates a driveway that lasts from one that disappoints.

A real-world Fraser Coast example

Picture two near-identical homes in Hervey Bay. Both pour a new driveway. The first owner stores a family car only and chooses 100mm with mesh on a properly compacted base, cured carefully through a hot week. Years later it is still sound.

The second owner stores a boat on a trailer and a caravan, but pours the same 100mm to match the neighbour’s price. The concentrated point loads from the trailer legs and jockey wheels work on the thinner slab season after season, and with the reactive soil moving underneath, cracks appear and spread. The “cheaper” driveway ends up costing far more.

The difference was never the concreter or the concrete — it was matching the slab to the real-world use. That is the whole point of getting thickness and reinforcement right from the start.

Get the right spec for your driveway

The right thickness for your driveway depends on how you use it and what the ground underneath is doing. Rather than guess, it is worth having someone who knows Fraser Coast soils and climate assess your site.

We pour concrete driveways across Hervey Bay, Maryborough, Rainbow Beach and Tin Can Bay, and we will spec your slab to last — the right thickness, the right reinforcement and proper base prep. Get in touch for a written quote and we will make sure your driveway is built for the loads it will actually carry.