Define the structure and obtain a design
Record use, dimensions, levels, thresholds, soil, climate, loads, buried services and relationship to the building. Give these details to the professional specifying the foundation, thickness, concrete, reinforcement, joints and interfaces.
No standard slab thickness or reinforcement suits every project. A suspended patio, fill, poolside area or heavy equipment requires project-specific assessment.
Excavate and prepare the formation
- 1Boards
- 2Joists
- 3Pedestals
- 4Compacted aggregate
- 5Geotextile
- 6Ground
Set out the work without damaging services, remove unsuitable soil as the design requires and install specified layers in properly compacted lifts. Check edges and levels throughout.
Estimate the excavation volumeTesCalculs→Plan falls, drainage and interfaces
- 1Finished level
- 2Sloping base
- 3Drainage away from the building
Route water away from the building and resolve outlets, thresholds and interfaces before formwork begins. Select any numerical fall to suit the finish, exposure and project specification.
Calculation example: a 1.5% fall changes level by 1.5 cm per metre. This explains the arithmetic; it does not prescribe the fall for your patio.
Install formwork, joints and reinforcement
Set stable formwork to the approved levels. Fix joints, openings, reinforcement and spacers in accordance with the design so they remain correctly positioned during placing. Do not tie the slab to the building without a designed detail.
Calculate volume and organise the pour
- 1Boards
- 2Joists
- 3Pedestals
- 4Compacted aggregate
- 5Geotextile
- 6Ground
Calculate each zone from its designed dimensions, then plan supply, access, labour and a sensible project allowance. Confirm the concrete class and workability with the specifier before ordering.
Calculate the volume of concrete to orderTesCalculs→Place, finish, protect and cure
Place the concrete without disturbing reinforcement, strike it to level and apply an exterior-appropriate finish. Protect the surface immediately using the specified method and observe the stated times before stripping forms, loading or adding a finish.