Building a Concrete Slab for Your Garden Shed
A solid concrete slab is the ideal foundation for any garden shed in Australia. Unlike timber bearers or pavers, a concrete base provides a level, permanent foundation that won't shift, rot, or allow pests to nest underneath your shed. Here's how to calculate and pour the perfect shed slab.
Why Concrete is Best for Shed Bases
Australian conditions demand durable foundations. Termites can devastate timber foundations, while pavers and gravel can shift over time. A concrete slab eliminates these concerns while providing a perfectly level surface that makes shed assembly straightforward. The slight additional cost compared to alternatives pays off in longevity and reduced maintenance.
Sizing Your Shed Slab
Standard 3x3 metre shed slabs suit most garden sheds and small workshops. However, consider making your slab 100-200mm larger than the shed footprint on each side. This extra concrete creates a useful apron around the shed entrance and allows for minor positioning adjustments during shed installation.
Drainage Considerations
Shed slabs should incorporate a slight fall away from the shed door, typically 1:100 (10mm per metre). This ensures rainwater drains away rather than pooling at the entrance. Set your formwork with this fall in mind, using a spirit level and calculated spacers to achieve the correct slope.
Anchor Bolt Placement
If your shed requires bolt-down anchors, plan their locations before pouring. Mark anchor positions on your formwork and have the bolts ready to insert into the wet concrete. Most shed manufacturers provide anchor spacing templates. Setting bolts during the pour is far easier than drilling into cured concrete later.
Council Requirements
Many Australian councils have specific requirements for shed construction, including slab specifications. Sheds over certain sizes may require development approval or building certification. Check with your local council before starting work, as requirements vary significantly between jurisdictions.
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.