Calculating Concrete for a Patio
Patios transform outdoor spaces into functional living areas, and concrete remains the most popular material choice for Australian homeowners. A 4x4 metre patio provides comfortable space for outdoor dining and entertaining while remaining achievable as a DIY project for those with reasonable skills.
Patio Size and Design
The 4x4 metre footprint accommodates a six-person dining setting comfortably, with space for circulation around furniture. Consider your specific furniture and intended use when finalising dimensions. Extending slightly larger is easier during construction than wishing you had more space later.
Slab Thickness for Patios
Patios typically only support foot traffic and furniture, making 100mm thickness adequate for most situations. This is thinner than driveways but provides plenty of strength for residential outdoor living areas. If heavy planters or spa equipment will sit on the patio, consider localised thickening at those points.
Drainage and Fall
Outdoor slabs must direct water away from buildings. Incorporate a fall of 1:100 (10mm per metre) away from the house. For a 4-metre wide patio, this means the outer edge sits 40mm lower than the house side. Set formwork carefully to achieve this consistent slope.
Connection to Existing House Slab
Where your patio meets the house, you have two options. Either pour directly against the house slab with an expansion joint between, or leave a gap filled with decorative stone. The expansion joint approach provides a seamless appearance but requires careful waterproofing to prevent moisture tracking along the junction.
Finishing Options for Patios
Patios offer more finishing flexibility than driveways. Smooth trowel finishes suit areas that will be tiled or coated later. Exposed aggregate creates an attractive, low-maintenance surface. Coloured concrete or stamped patterns can create impressive decorative effects. Consider maintenance requirements, as textured finishes can be harder to clean.
Furniture and Fixture Planning
If installing permanent fixtures like posts for a pergola or awning, plan their locations before pouring. Setting post brackets or anchors into fresh concrete is straightforward, but cutting and fixing into cured concrete is considerably more work.
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.