Concrete Slab Cost in 2026: House and Shed Slabs in Australia

A concrete slab costs about $90 to $140 per m² for a shed, garage or carport and about $110 to $170 per m² for a house slab on a standard site in Australia in 2026, including GST. Difficult soil, sloping blocks and small extension slabs can push the rate to $200 per m² or more.

Those per m² figures cover the slab itself: formwork, reinforcement, concrete, pumping and finishing. On a house, there is a second layer of site costs around it, such as soil testing, engineering, site cuts and termite protection, that can add several thousand dollars. This guide explains both. It focuses on structural slabs for buildings. For driveways, see the concrete driveway cost guide, and for a broad overview of concreting jobs, the concreting cost guide. Figures are indicative, and you should get at least three written quotes based on engineered drawings.

Slab prices per m² by type

What common slab sizes cost

Small slabs cost more per square metre because every pour has fixed costs: getting the crew and gear to site, the concrete plant's small-load fees, and often a pump. The table below shows typical totals for the slab only.

For a house, the slab is usually part of the builder's contract rather than a separate job. Even so, knowing what it is worth helps you read a builder's quote and judge site cost allowances.

The ground decides the slab

Before anyone designs a house slab, a geotechnical engineer drills test holes and classifies the site under AS 2870, the Australian standard for residential slabs and footings. The classification describes how much the soil swells and shrinks with moisture. Reactive clay moves a lot, and a slab on it needs deeper, stiffer beams and more steel.

A soil test with site classification usually costs $600 to $1,500. Engineering design for a house slab is often $1,200 to $3,500. Builders sometimes include both in a fixed "site costs" figure, so ask for the soil report early. It is the single best predictor of whether your slab budget will hold.

Trees matter too. Large trees near the building footprint dry out clay soils unevenly, and the engineer may call for deeper footings. Sites where trees have recently been removed can also behave unpredictably as the soil rehydrates.

Waffle pod, raft or something else

Waffle pod slabs sit on the ground and use polystyrene pods to form a grid of ribs under a thin top slab. They use less concrete and excavation than a conventional raft and are quick to build, which is why most volume builders use them on flat A, S and M class sites. The pods also give a small insulation benefit.

Stiffened raft slabs have deeper edge and internal beams dug into the ground. They suit reactive clay, sloping sites where the slab steps, and situations where the engineer wants more stiffness. They use more concrete and labour.

Pier and beam or piered slabs transfer load down to firm ground through bored piers or screw piles. They are common on P class sites, filled land and steep blocks. Each pier adds cost, and the total depends on depth and number.

Shed and garage slabs are usually simple 100 mm slabs with mesh and thickened edges, sometimes with deeper pads under portal frame posts. Shed kit suppliers normally provide the engineering and footing details for the slab, which your concreter should follow.

What is in the slab price, and what sits outside it

Comparing slab quotes gets confusing because different contractors include different things. As a guide:

Usually in the slab rate: formwork and edge boards, vapour barrier (a polyethylene membrane under the slab), waffle pods or beam excavation, reinforcement and bar chairs, concrete supply, pump, placing, finishing and curing.

Often outside it:

• Soil test, engineering design and surveyor set-out.
• Site cut, fill and retaining on sloping blocks, which can range from a couple of thousand dollars to well over $10,000.
• Termite management, which the building code requires in most of mainland Australia and is commonly $1,500 to $4,000 for a house.
• Under-slab plumbing and drainage, which is a licensed plumber's work and priced separately.
• Electrical conduits cast into the slab, done by an electrician.
• Slab edge insulation where the energy efficiency rules in your climate zone call for it.
• Rock excavation, removal of spoil and contaminated material.
• Polishing, if the slab will be a finished floor. The concrete flooring cost guide covers polishing prices, and planning it before the pour saves money.

Slab costs around the country

Typical per m² rates vary with labour, concrete prices and soil conditions in each region.

Three slabs, costed

Colorbond shed slab near Gympie, 6 m x 9 m

A 54 m² shed for a ute, trailer and workbench on a rural block. Flat site with good truck access. The shed supplier's engineering called for thickened edges and pad footings at each portal post.

The truck backed straight up to the formwork, so no pump was needed. With a pump the total would have been closer to $8,300.

Waffle pod house slab in Wollert, 220 m²

A single-storey four-bedroom home on a flat M class block. This example breaks out the site costs that builders often bundle together.

The slab work alone, from pods to finishing, came to about $125 per m² including GST. The site costs and inspections added roughly $10,000 on top. Under-slab plumbing was in the plumber's contract and is not shown.

Rear extension slab in Prospect, 30 m²

A family room extension on an H1 clay site, dowelled into the existing house slab. Access was down a side path, so everything went in by barrow and line pump.

The slab components alone worked out at about $208 per m² including GST. Small extension slabs carry the same design, inspection and mobilisation costs as larger ones, so the all-in price per square metre looks high. The house extension cost guide shows how the slab fits into the wider budget.

Approvals, inspections and who can do the work

A house or extension slab is part of the building approval. Depending on your state, that is a development application or complying development certificate in NSW, a building permit in Victoria, Tasmania and WA, or a building approval through a private certifier in Queensland. The approved drawings and engineering set the slab design, and the reinforcement is normally inspected by a certifier or engineer before the pour. Do not let anyone pour without that inspection; it is very hard to fix afterwards.

Sheds are simpler but not always approval-free. In NSW, small garden sheds can be exempt development if they meet the conditions in the state codes, including size limits, and the NSW Planning Portal sets those out. Larger sheds and garages usually need approval in every state, along with engineering for wind loads. Check with your council or a private certifier before ordering the kit.

Licensing follows the value and type of work. Slabs for new houses are done under a licensed or registered builder. For a standalone slab, NSW requires a licensed contractor and written contract for residential work over $5,000, Queensland's QBCC requires a licence for building work valued over $3,300, and in Victoria you should confirm registration and contract requirements with the Building and Plumbing Commission. Owner-builders in most states need a permit above a set value, so check the current threshold with your regulator before taking on a house slab yourself. Under-slab plumbing must be done by a licensed plumber and inspected, and any conduits for power need a licensed electrician.

The Australian Building Codes Board publishes the National Construction Code, which sets the performance requirements behind termite management, damp-proofing and energy efficiency for slabs. Termite management for new buildings is covered in AS 3660.1, and your builder or pest manager will choose a compliant system.

Can you pour a slab yourself?

A small garden shed pad or tank base is a reasonable DIY job for someone handy, especially with pre-mixed bags for anything under about half a cubic metre or a mini-mix truck for slightly more. You will need formwork timber, mesh, chairs, a screed board, floats, an edging tool and at least one helper.

Beyond about 10 to 15 m², the economics change. Concrete arrives in a truck, starts setting quickly and needs a practised crew to place and finish before it goes off. Garage and shed slabs also need to be level and square for the kit to fit, and the hold-down bolts have to be in the right place. Most people who DIY a large slab say they would pay a concreter next time.

Where you can save is the preparation: clearing vegetation, digging out topsoil on small jobs, moving materials and cleaning up. Agree the split with your concreter first so nothing they rely on gets skipped. For a sense of what concreters charge for their time, see the concreter hourly rate guide.

What makes a slab cost more than expected

• Slope. Every metre of fall across the site means more cut, fill, retaining or deeper edge beams. A step in the slab adds formwork and engineering.
• Rock. Hitting rock during excavation brings in rock breakers or bigger machines, usually charged by the hour.
• Fill. Uncontrolled fill on older or subdivided land often means piers down to natural ground.
• Access. Narrow side access, power lines and steep driveways mean boom pumps, smaller machines and more labour.
• Weather. Rain before the pour can flood beam trenches and set the job back. In hot weather, crews may start before dawn and use retarders.
• Waste. Spoil from excavation has to go somewhere. Tip fees for clean fill are lower than for mixed or contaminated soil, which can be expensive.
• Changes. Moving a wall or plumbing fixture after the slab is designed means redesign and possibly re-inspection.

Keeping the slab budget under control

Most slab cost blowouts are site surprises, not concrete prices. A few decisions early on make a real difference.

• Get the soil test before you sign. A fixed-price build contract with a provisional allowance for site costs can move by thousands once the report comes back H2 or P class.
• Choose the building pad carefully. On a sloping block, siting the house or shed where the fall is gentlest cuts excavation and retaining costs.
• Keep the footprint simple. Rectangles are cheaper than L shapes with lots of corners, set-downs and steps.
• Plan set-downs early. Recesses for showers, tiles or a level entry are cheap when designed in and expensive as a later fix.
• Combine pours. If you need a shed slab, a path and a carport pad, pouring them on the same day saves on mobilisation and pump hire.
• Sort spoil disposal upfront. Ask whether excavated soil can be spread on site, which avoids truck and tip fees.

Be careful about cutting the wrong things. Thinner slabs, lighter mesh than specified or skipping the vapour barrier save a few hundred dollars and can cost tens of thousands in cracking and damp later.

Questions for your concreter or builder

• What site class is my block, and can I see the soil report?
• What slab type and concrete strength are specified, and who designed it?
• Is the pump, vapour barrier, termite management and set-out included?
• How will spoil be removed, and is that in the price?
• Who books and attends the pre-pour inspection?
• What are the provisional sums or allowances, and what happens if rock or fill is found?
• What is your licence number, and do you carry public liability insurance?

Red flags include a refusal to work from engineering drawings, a quote with no mention of the soil class, cash-only pricing, and a large upfront deposit beyond what your state allows.

From set-out to a cured slab

A shed slab usually takes two to three days on site: preparation and formwork, steel, then the pour. A house slab is more like one to two weeks from set-out to pour, depending on plumbing rough-in, inspections and weather. After the pour, concrete gains most of its design strength over about 28 days. Builders can usually start framing within a week or so, but heavy loads, such as stacked bricks or a crane, should wait until the engineer is satisfied.

Curing matters. Keeping the slab damp or using a curing compound in the first days reduces surface cracking and dusting, especially on hot, windy days. Hairline shrinkage cracks are common and are usually cosmetic. Wider or uneven cracks are worth a call to the builder.

Where Yakka can help

Slab projects have plenty of labour that does not need a concreter or builder. Clearing a shed site of old timber and rubbish, digging out topsoil by hand where a machine cannot reach, barrowing base material, carrying formwork and mesh, and cleaning up after the pour are the sort of jobs you can book a worker for on Yakka Labour. The guide on how to hire a labourer for a day explains rates and how bookings work.

The slab itself should go to an experienced concreter or your builder, working from engineered drawings and with the licence your state requires. You can compare local concreters, and for site cuts and bigger digs, excavation contractors on the platform.