The short answer
Shed and garage slabs across Newcastle and Lake Macquarie run $110 to $150 per m² supplied and laid. Small slabs sit at the top of that range, large simple ones towards the bottom.
| Shed or garage | Slab size | Guide price |
|---|---|---|
| Garden shed, 3 x 3 m | 9 m² | $1,000 to $1,350 |
| Large garden shed, 4 x 3 m | 12 m² | $1,300 to $1,800 |
| Single garage, 6 x 3.5 m | 21 m² | $2,300 to $3,150 |
| Double garage, 6 x 6 m | 36 m² | $4,000 to $5,400 |
| Workshop, 9 x 6 m | 54 m² | $5,900 to $8,100 |
| Large shed, 12 x 7 m | 84 m² | $9,200 to $12,600 |
Published rates are a guide for budgeting. The price for your job is the one on the written quote after a site measure.
Why small slabs cost more per metre
A crew, a truck, formwork and a minimum load of concrete cost much the same whether the slab is 9 m² or 20 m². Spread over fewer metres, those fixed costs push a garden shed base to the top of the range. It is also why a shed slab is cheapest when it is poured with something else, a path to reach it, a patio, or a driveway extension.
Thickness and steel by use
The shed supplier’s engineering governs. As a guide to what those documents usually ask for:
- Garden sheds and light storage: around 100 mm with mesh, on a prepared base.
- Garages and carports taking cars: commonly 100 to 125 mm with heavier mesh and thickened edges under the frame.
- Workshops with a hoist, a lathe or stored machinery: local thickening under point loads, designed for the load you describe.
- Every slab: mesh on chairs so it sits inside the concrete, a door rebate where a roller door needs to seal, and hold-down positions taken from the drawings.
Slabs for dwellings and granny flats are a different, certified process and are not referred through this site. The specification sets the build out in more detail.
Two checks before you order the kit
Access. Most sheds go in a back corner a truck cannot reach. If the chute will not get there, the concrete is pumped or barrowed, and that is priced in the quote. Measure the side passage and note gates, steps and overhead lines.
Mine subsidence. Large parts of Newcastle and Lake Macquarie sit inside declared mine subsidence districts. Subsidence Advisory NSW publishes a list of exempt development, and structures outside that list may need to meet its guidelines, which can change the slab. Search your address on the NSW Planning Portal Spatial Viewer first. It takes two minutes and it is free.
Ground
West of the city the ground is mostly reactive clay, which swells when wet and shrinks when dry. A shed slab there depends on the base being cut to firm material and compacted where the ground calls for it, or the slab rocks and cracks at the door. Near the coast and the lake, sand drains well but needs confining at the slab edge. Sloping blocks need a cut, a filled and compacted pad, or a thickened downhill edge.
What else the quote should say
Ask for the slab size, thickness, mesh, concrete strength, edge detail, rebate, how the concrete reaches the pour, and what happens to the spoil. If a new or wider crossing is needed to get a boat or trailer to the shed, that part needs council approval under the Section 138 process. Compare everything against the cost guide, and where old concrete has to come out first, allow about $35 per m² for removal. The full service page is shed and garage slabs, and decorative options are on the exposed aggregate page.