ConcreteslabsinAdelaide:house,shed,garage,andfootings
A 30m2 shed slab in Adelaide runs $4,800 to $8,500 including mesh, formwork, and vapour barrier. Reactive clay sites in the north-west need higher footings. We connect you with BWC-licensed concreters who design to AS 2870.
Why Adelaide soil class determines your slab cost
Adelaide sits on a wide range of soil classes. The coastal and inner-western suburbs (Glenelg, West Torrens, Charles Sturt) are largely stable sand and Class S. The inner east and foothills (Burnside, Mitcham, Tea Tree Gully) carry moderately reactive clay pockets (Class M). The northern corridor (Playford, Gawler) has pockets of Class H highly reactive clay.
A 100mm slab on Class M soil without proper footings lifts, drops, and cracks within the first year as the clay swells and shrinks through winter rainfall and summer drought cycles. Most lump-sum slab quotes do not state the soil class or footing design. You find out at year 1 when the slab moves.
AS 2870 sets the minimum footing design for each soil class. Class M sites typically need a stiffened raft or screw piles. Class S sites use standard strip footings. The footing design is not optional - it is what keeps the slab flat for 30 years.
Shed slab vs garage slab vs house slab: spec differences
A shed slab for a standard backyard workshop runs 100mm, SL72 mesh, 25 MPa, strip footings to AS 2870 for the soil class. A 30m2 shed slab in Adelaide ranges $4,800 to $8,500.
A garage slab for standard residential use (family vehicles) runs 100mm minimum, SL72 mesh, 25 MPa. A 60m2 double garage slab ranges $7,500 to $13,500. If the garage accommodates a heavy trade vehicle or a car lift, the spec moves to 125mm, SL82, 32 MPa.
A house slab is the most complex because it integrates with the footing system and interacts with council and engineering requirements. The concreter works from the structural engineer's design drawings. Where soil class is Class M or H, an engineer's certificate is standard.
What an itemised slab quote looks like
Every slab quote from the network states: slab dimensions and area, slab thickness in mm, mesh grade, mix strength in MPa, footing type and depth, soil class assumed (or soil report reference), vapour barrier specification, and any engineering certification required.
For slabs above $20,000 inc GST, the BWC licence number of the concreter appears on the quote and is verifiable on the SA CBS public register. The Builders Warranty Insurance certificate is issued before work starts. Full details at BWC licensing in SA.
Cure time for slabs follows the same milestones as driveways: foot traffic from day 2, vehicles at 7 days, loading at 28 days. For house slabs, framing does not start until the engineer signs off on the slab cure.
Related services and cost guides
Concrete slab cost Adelaide - shed, garage, and house slab price breakdown by soil class.
Concrete repair - settlement diagnosis and rectification for existing slabs.
Cure, cracks, and control joints - the 28-day cure milestone and crack types explained.
Area coverage: slabs poured across Mitcham, Tea Tree Gully, Salisbury, and Playford.