How Much Concrete for a 6x3 Metre Shed Slab
A 6x3 metre slab is a substantial foundation suitable for single garages, large workshops, or multi-bay storage sheds. At 18 square metres, this size marks the point where professional assistance or ready-mix concrete becomes almost essential for most DIYers.
Volume Calculations Explained
The 6x3 metre footprint at 100mm depth produces 1.8 cubic metres of concrete, or approximately 1.98 cubic metres with standard 10% wastage. This equates to around 214 bags of premix concrete, making ready-mix the only practical option for most situations. Attempting to hand-mix this quantity would require exceptional stamina and risk inconsistent concrete quality.
Structural Considerations for Larger Slabs
Slabs of this size warrant more attention to structural details. Consider upgrading to SL82 mesh for improved crack resistance, particularly if heavy equipment will be stored on the slab. Ensure your subbase is thoroughly compacted, as any settlement in a slab this size can create noticeable cracking patterns.
Pour Logistics
A 2 cubic metre pour requires efficient organisation. Have sufficient workers on hand, typically 3-4 people for a slab this size. One person manages the concrete flow, while others spread, level, and consolidate. With approximately 45-90 minutes of working time before initial set, everyone needs to know their role before the truck arrives.
Finishing Techniques
For shed bases, a broom finish provides adequate grip while being easy to achieve. After screeding and bull-floating, wait for the bleed water to evaporate before dragging a stiff broom across the surface in parallel strokes. This creates a slip-resistant texture that's practical for workshop environments.
Cost Comparison
At this volume, ready-mix concrete typically costs between $560 and $840 for the concrete alone, plus delivery fees of $100-200. While bags might appear cheaper on paper, the time, labour, and equipment hire for mixing makes ready-mix the more economical choice. Check our bags vs ready-mix comparison for your specific situation.
Need Different Dimensions?
Use our concrete slab calculator to enter your exact measurements and get instant results. You can also compare bags vs ready-mix costs for your specific project volume.