Concrete Slabs in Pakenham
A slab has one job: transfer a load into the ground without cracking. What’s on top — a shed, a garage, an alfresco, a workshop — only tells you how much load. The rest of the design is decided by the ground itself.
This page covers the residential and light commercial slabs we build across the Cardinia corridor. For the slab that sits under your concrete driveway it’s a similar build with a different specification; for anything on Council land, see vehicle crossing.
What we build
The slabs we pour, broadly:
- Shed and garage slabs — the most common job on new estate blocks. Designed to the shed manufacturer’s footing schedule or the engineer’s detail, with thickened edges where the columns and rolls land.
- Alfresco and outdoor room slabs — tied into the house slab where possible, or isolated with an expansion joint where movement between the two is a risk.
- Workshop and outbuilding slabs — heavier reinforcement, thicker section, sometimes with pit or trench detail if there’s machinery involved.
- Extension and addition slabs — poured against an existing slab, with dowel connection into the old slab and matched levels through a construction joint.
- Water tank and equipment pads — smaller footprint, higher point load, designed to the manufacturer’s base spec.
Cosmetic paths and steps are their own build; that’s covered on the concrete path page.
How a residential slab is actually designed
There are two Australian Standards behind every slab we pour. Worth naming them, because they’re the answer to most of the questions people ask about pricing.
AS 2870 covers the design of residential slabs and footings on reactive soil. It sets your site classification — the label you’ll see on your soil report, running from A (stable) through S, M, H1, H2 to E (extreme). The class decides how deep the edge beams go, how much reinforcement is in the raft, and whether you can get away with a raft slab at all or need a stiffened raft or a waffle pod.
AS 3600 covers the concrete itself — strength, cover to reinforcement, and durability. It’s how the engineer arrives at “25 MPa, 40 mm cover” and it’s why an engineer’s detail is worth what it costs.
What that means practically: the honest answer to “what does a shed slab cost in Pakenham?” is that we can’t tell you without a shed size, a shed weight, and a site class. Any concreter who gives you a per-square-metre number over the phone is guessing at two of those three and hoping the third averages out.
Site class, and why yours matters more than the postcode
Site classification is a laboratory result from your lot. It’s derived from shrink-swell testing on samples from a real geotechnical investigation, and it’s sensitive: a small change in the measured index moves the site up a class, and earthworks on the block can change the answer again.
The Pakenham corridor isn’t one uniform sheet of anything. The geology through here is basalt valley flows separated by ridges of older basement, under a veneer of sand and clay, with alluvium along the creeks. Which is why the site class of the block next to yours doesn’t tell you your site class.
If you’ve built recently, you already have a soil report — it came with your slab documentation. Send it with your enquiry. If you don’t have one, we’ll tell you when you need to commission one and when a suitably-detailed engineered raft can cover the ground.
What actually goes into the ground
The build order below is what a good slab looks like, in order.
Set-out and box
String lines from the boundary or from the house, squared to the block and levelled. Formwork boxed to the engineer’s dimensions with allowance for thickened edges and any step-down or rebate. On sloping sites, the fall is set into the box; you don’t correct fall in the pour.
Subgrade, base and moisture
Topsoil stripped to firm natural or to the level the report specifies. Base is 50 mm of 20 mm class 3 crushed rock, mechanically compacted, blinded with sand where the plastic will sit directly on it.
A 0.2 mm vapour barrier under the slab is standard on any habitable or heated space, and cheap insurance on a shed. Laps sealed, penetrations taped, no punctures from the mesh chairs.
On reactive sites — M and up — the edges are dug deeper for stiffening beams, and the ground under the beams is inspected before steel goes in.
Reinforcement
Mesh sits on bar chairs at the top of the slab with 40–50 mm cover to the finished surface. Edge beams carry trench mesh or bar and ligatures, sized by the engineer.
Two things separate a reinforced slab from a slab with mesh in it. The first is cover — steel too close to the top eventually rusts and spalls, steel too low does no work. The second is continuity — mesh laps are two full squares tied, and edge steel is bent into corners, not butted. If a quote says “mesh throughout” but doesn’t specify chairs, cover or lap, that’s the difference between an engineered slab and a slab-shaped mistake.
Concrete, pour, and finish
Standard residential slab is 25 MPa (N25), sometimes 32 MPa where the engineer calls for it. Placed continuously, screeded, bull-floated, then finished to the surface required — a broom finish for shed and utility slabs, a steel trowel for garages and workshops where a cleaner surface matters.
Where a slab is going to carry a fitted floor covering, we leave it flat and float-finished rather than trowelled to a polish — a polished slab looks impressive on handover and then fights every glue and screed you put on top of it.
Joints and curing
Control joints saw-cut on time, spaced to the slab depth. Isolation joints against the house, adjoining slabs and any fixed structure. Curing is either a plastic cover, a wet cure, or a curing compound — picked to the weather on the day of the pour, not to a policy.
A shed slab that surface-dries in a hot easterly ends up crazed, weaker at the surface, and dusty forever. Curing is a real line and it’s the difference between a slab that hits its design strength and one that hits 70% of it.
Slab-on-ground versus waffle raft: what you'll actually get quoted
Two systems, both valid, priced differently.
Slab-on-ground (conventional raft) — excavated edge beams filled with concrete, mesh in the top of the slab. Heavier on concrete and steel, lighter on setup. Handles reactive sites well and forgives site variation.
Waffle pod raft — polystyrene pods on top of the ground, the slab and beams poured over them. Faster to set up, less excavation, uses less concrete. Sensitive to poor site preparation and unsuited to some reactive sites.
Neither is “better.” The right one is the one your soil report supports, the one the engineered detail specifies, and the one that fits your budget once both are drawn up. If you’re getting quotes that don’t tell you which system is being priced, ask.
Where we work
Slabs are the same specification wherever you build them, but access, setback and easements aren’t. If you’re after a concreter in Officer, most jobs are new-estate blocks with tight access down the side of the house; if you’re after a concreter in Berwick, the older lots and treed sites often have street tree and easement conditions on where a shed can go.
For the rest of what we build and how we quote, see concreters in Pakenham.
Send the slab size, what’s going on it (shed brand and model, garage plans, alfresco drawings), and your soil report if you have one. We’ll come back with the specification, the reinforcement schedule and the joint layout — not a per-square-metre number pulled out of the air.