Slab guide · Slabs & new builds
Shed slab guide: size, thickness and footings
By Nathan Carter, owner, Gold Coast Concrete Services. Reviewed October 2026.
Quick answer
A shed slab should be sized to your shed kit's exact external dimensions, usually with a small allowance so the wall sheeting sits just past the slab edge to shed water. Most garden and garage sheds sit on a 100 mm slab with SL82 mesh, with thickened edges or pier footings where the shed engineering requires them. Larger sheds often need building approval, and the shed's engineering sets the footings.
| Shed type | Typical slab | Footings |
|---|---|---|
| Small garden shed | 75–100 mm, SL72–SL82 mesh | Thickened edges |
| Garage or workshop shed | 100 mm, SL82 mesh | As per shed engineering |
| Large or portal-frame shed | 100–150 mm, as engineered | Pier footings at columns |
| Vehicle or machinery shed | 125–150 mm, heavier mesh | As per shed engineering |
Start with your shed plans
Every shed kit comes with plans showing its external size, column positions and footing details. We set out the slab from those plans so the frame sits square and level.
Most kits want the slab finished a few millimetres inside the wall sheeting, so rain runs off the cladding rather than onto the slab and under the walls. Check your kit’s instructions, or send them to us and we’ll check.
Thickness and steel
Small garden sheds can sit on a lighter slab. Garages and workshops that take cars, tools and benches are usually 100 mm with SL82 mesh. If you plan to park a boat, caravan or machinery inside, go thicker with heavier mesh.
Footings and hold-downs
Wind is the big load for sheds in South East Queensland. The shed’s engineering usually specifies pier footings or thickened edges at the columns, and how the frame is bolted down. We pour these with the slab and can set cast-in bolts or leave the slab ready for drilled anchors.
Levels, falls and access
A shed slab should be level inside, with the ground outside falling away so water doesn’t run in. If you want a roller door with a small step-down or a rebate to keep water out, tell us before the pour. Plan the apron or path to the door at the same time.
Approvals
In Queensland, small sheds can often be built without approval, but larger sheds, sheds close to boundaries and sheds in some zones need building approval. Your shed supplier or a building certifier can confirm what applies to your shed and block.
Common questions
How soon can I put my shed up?
Light frame work can usually start after about seven days. Wait for full strength before parking heavy vehicles or machinery inside.
Can a shed go on an existing slab?
Sometimes, if the slab is the right size, level and strong enough, and can take the hold-down bolts. Large sheds usually need new footings.
Do you supply the shed kit?
No. We prepare and pour the slab to suit your kit. Your shed supplier provides the plans and engineering.
Should a shed slab be sealed?
Sealing helps resist oil and dust in workshops. You can also add an epoxy or flake coating later.
