Pre-pour inspection (slab)
Pre-pour inspection is the certifier hold-point before slab concrete is poured: subgrade, formwork, reo, vapour barrier, termite cert, service penetrations.
Ask Chalkline about this →A pre-pour inspection is the mandatory certifier (or accredited inspector) hold-point that takes place before slab concrete is poured, verifying that the subgrade preparation, formwork, reinforcement, services, vapour barrier, and termite-treatment certification all comply with the design and the relevant standards. It is one of three critical slab-stage inspections (the others being excavation/footing inspection for deeper footings, and floor framing inspection for any framed sub-floor before lining). Without certifier sign-off at the pre-pour inspection, the concrete truck does not arrive. Verified per AS 2870:2011 and AS 3600:2018 (2026-05-16).
What the certifier checks at pre-pour inspection:
| Element | Verification |
|---|---|
| Subgrade preparation | Compaction to specified density; correct sand or gravel base; level and even surface |
| Vapour barrier | Continuous, lapped 100-200 mm at joints, sealed at penetrations, AS 2870-compliant grade |
| Formwork | Square, plumb, secure; correct slab dimensions; properly braced; release agent applied |
| Reinforcement (mesh + bars) | Correct grade and size per engineer’s drawings; correct spacing; correct top/bottom positioning |
| Concrete cover | Bar chairs set to deliver specified cover (typically 40-50 mm bottom, 25 mm top); cover measured at sample points |
| Lap lengths and tie-backs | Reinforcement laps meet AS 3600 minimum (typically 40 bar diameters); ties placed at correct frequency |
| Termite barrier certificate | Issued by pest management technician, referencing AS 3660.1 product and application date |
| Service penetrations | Plumbing rough-in, electrical conduits, water supply all positioned and supported; no clashes with reinforcement |
| Drainage and falls | Slab edge falls correct for site drainage; drainage layer below slab if specified |
| Hold-down bolts and anchor cast-ins | For wall framing connections; positioned per drawings |
Why these elements matter:
| Element | Risk if not inspected |
|---|---|
| Subgrade | Slab settles unevenly; reactive ground causes deflection |
| Vapour barrier | Moisture rises through slab; flooring fails, fungal growth |
| Reinforcement | Slab cracks under load; structural failure |
| Cover | Reo corrodes; spalling within 15-30 years |
| Termite barrier | Termite breach; legal exposure to builder |
| Penetrations | Plumbing in wrong location; re-cut and patch needed |
The hold-point sequence:
- Builder/concretor builds up to pre-pour state: formwork, vapour barrier, reo, services, hold-down cast-ins all in place.
- Builder notifies certifier at least 24-48 hours before planned pour (longer in busy markets).
- Certifier inspects on-site.
- Certifier signs off in writing (typically a Form 6 or equivalent in each state).
- Concrete truck arrives, slab poured.
- Without certifier sign-off, no pour: the certifier’s signature is the legal hold-point release.
Common defects found at pre-pour:
- Vapour barrier torn or missing patches: re-lay or patch with overlapping tape.
- Reinforcement positioned wrong (top reo on bottom, etc.): re-position before pour.
- Bar chairs too few: bars sag below the design level; cover insufficient at sag points.
- Termite certificate not yet issued: builder must call the pest management technician back to issue or re-treat.
- Plumbing penetration clashes with reinforcement: drill through reo (avoid) or re-route services.
- Engineer-specified mesh substituted with cheaper grade: refusal until correct mesh installed.
Outcome of inspection:
| Outcome | Action |
|---|---|
| PASS | Sign-off issued; pour can proceed |
| PASS WITH NOTES | Specific items to fix before pour (e.g. add more bar chairs); re-inspection at the pour |
| FAIL | Major items missing or incorrect; full re-inspection required; pour delayed |
Builder’s pre-inspection self-check:
- Walk the formwork checking square (5-4-3 method or laser).
- Pull out a piece of reo to verify cover (place a piece of timber across the slab, measure to a bar; cover should match the spec).
- Inspect every service penetration; confirm sleeve, ducting, support.
- Verify the vapour barrier seal at every penetration.
- Have the termite certificate in hand.
Documentation retained:
- Pre-pour inspection sign-off (legal record).
- Certifier’s photographs.
- Termite barrier certificate.
- Reinforcement supply dockets matching spec.
- Concrete order docket matching the engineer’s mix design.
Also known as: pre-slab inspection; reo inspection; pre-pour hold-point; mesh inspection; slab inspection; F1 inspection (in some certifier nomenclature).
Category: Inspection.
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Last updated: 2026-05-16. Verified: 2026-05-16. Quarterly review for currency.