The slab is the stage where mistakes become literally set in concrete — and also the stage where a first-time owner-builder has the least feel for what “right” looks like. This guide walks the sequence, the pre-pour inspection that anchors it, and the discipline that makes pour day boring (which is the goal).
The sequence, in order
- Siteworks and set-out — cut/fill to design levels, surveyor’s set-out pegs. Errors here propagate to every later trade; a set-out check against the site plan is minutes well spent.
- Service rough-ins — plumber and electrician run everything that lives under the slab. Once poured, a missed conduit is a concrete saw and an argument.
- Formwork, membrane, mesh and pods — the slab system assembled to the engineer’s drawings: vapour barrier lapped and taped, reinforcement at specified cover on chairs, edge beams and thickenings where drawn.
- Pre-pour inspection — the certifier (and in some arrangements the engineer) inspects before any concrete arrives. This is a mandatory-stage inspection: no sign-off, no pour.
- The pour — booked with weather margin, a pump, enough hands, and the finisher’s runsheet agreed.
- Curing — the cheapest structural insurance there is, and the step most often skipped in summer.
What the certifier is actually looking at
- Set-out and levels against the approved plans — boundary setbacks especially.
- Reinforcement: size, spacing, laps and cover (the concrete between steel and ground/air) per the structural drawings.
- Membrane integrity — punctures taped, laps correct, brought up at edges.
- Under-slab services in place, tested where required, penetrations sleeved.
- Edge beams, piers and thickenings matching the engineer’s design for your soil classification.
Your job isn’t to re-inspect their inspection — it’s to have the site ready so the inspection passes first time. Every failed inspection is a rebooking fee plus days of drift; run the delay-cost counter to see what your drift week costs.
Pour day discipline
- Concrete is ordered against the engineer’s spec — strength grade and slump are on the drawings, and the docket that arrives should match. Keep every docket.
- Water stays out of the mix on site. “A splash to help it flow” trades workability now for strength forever. The fix for stiff concrete is the pump and the crew, not the hose.
- Weather margin is real: a slab poured into a storm, or into 38° with no plan, becomes a defect negotiation.
- Photos of everything before it disappears — membrane, steel, conduits. Five minutes of photos is your evidence file for the next six years.
The paperwork this stage generates
Collect as you go: the pre-pour inspection record, concrete delivery dockets, the plumber’s under-slab test results, termite system certificate (where installed at slab), and your photo set. This is the start of the certificate trail that becomes your handover pack — and your defence file if anything is ever disputed.
Before you get here
Everything above goes smoother if it was sequenced on paper months earlier — quotes levelled, inspection schedule mapped, budget lines checked against reality. That’s precisely the job of the Pre-Start Review: $790, one week, and the slab stage arrives with no surprises left in it.