Concrete Slab Thickness Guide: How Thick Should Your Slab Be?
Slab thickness is one of the most common questions we get. Get it right and your slab will hold up for decades. Get it wrong and you'll see cracks, settlement or worse. Here's a straight-talking guide to the thicknesses we use across Wollongong, Shellharbour, Shoalhaven and the Southern Highlands.
Residential Driveways
For standard cars and light 4WDs, 100mm reinforced with SL72 mesh is the standard. If you're parking a heavy 4WD, caravan, boat trailer or work ute, step up to 125mm with SL82 mesh. Crossovers must meet your local council spec — usually 150mm.
Garage & Shed Slabs
A typical residential garage slab is 100mm with SL72 mesh on a compacted base. Larger sheds, workshops or anything housing heavy equipment should be 125–150mm with heavier reinforcement and thickened edges.
House Slabs
House slabs are engineer-designed to AS 2870. Waffle pod, raft and stiffened raft slabs are common on the South Coast, with thickness and beam depths set by the soil classification (M, H1, H2 etc). Never DIY a house slab — always work from an engineer's drawings.
Patios, Paths & Alfresco
75–100mm is fine for foot-traffic patios and paths. We use 100mm with SL72 mesh as standard so the slab has long-term durability and can take occasional load (a wheelbarrow, an outdoor kitchen, etc).
Heavy-Duty & Commercial
Driveways for trucks, forklift areas, industrial floors and commercial pavements start at 150mm and go up from there, with engineered reinforcement and a properly designed base. We handle these regularly — see our commercial concrete page for more.
What Else Matters
Thickness alone isn't enough — the base prep, reinforcement, concrete strength (typically 25–32 MPa), control joints, curing and edge thickening all matter just as much. We design every slab to suit the use, the soil and the site.
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Serving Wollongong, Shellharbour, Shoalhaven and the Southern Highlands. License 376227C — fully insured.
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