Slab Inspection
An independent check of the completed slab against AS 2870 and the engineer's detail — after the pour, before the frame goes up.
Book before backfill covers the slab edge
Why a Slab Inspection Matters
The slab is the foundation the rest of the house is built on. Once the frame is stood and the perimeter is backfilled, the edge beam, the membrane turn-up and the termite collars are hidden. The slab inspection is the window to confirm the finished slab matches the engineer's design before that happens.
A residential slab in South East Queensland is engineered to AS 2870 Residential slabs and footings for the site's soil classification — commonly M, H1 or H2 reactive clay across the Moreton Bay, Logan and Ipswich corridors. The classification sets the slab and beam design; the wrong system for the site class, or an under-dimensioned edge beam, is the kind of departure this inspection is designed to catch.
Slab and footing defects that surface after handover are among the most expensive to rectify — remedial underpinning or edge-beam repair is disruptive and slow. Confirming the slab now is far cheaper than dealing with movement later.
What's Included
- Slab thickness and edge beam dimensions vs engineering
- Concrete cover at exposed edges (AS 3600)
- Slab classification correct for site class (AS 2870)
- Set-out checked against architectural drawings
- Service penetration locations (plumbing, electrical)
- Vapour barrier condition and taping at penetrations
- Termite barrier integrity (AS 3660.1)
- Surface condition — cracking, honeycombing, plane
- Same-day PDF report with photos
Includes GST
Critical Elements We Verify
Dimensions
Thickness and edge beams vs engineering
Classification
Slab type correct for the site class
Membrane
Vapour barrier condition and laps
Termite
Barrier system per AS 3660.1
What we check on a completed slab
The checklist works methodically around the slab, referencing the engineer's detail and the relevant Australian Standard for each item. NCC Volume Two clauses 3.3.5 (site preparation) and 3.3.6 (slabs) set the acceptable-construction baseline; AS 2870 and AS 3600 carry the engineering detail.
- Slab thickness and edge beam dimensions — measured against the engineer's slab detail. Depth and edge-beam width are the primary structural dimensions and are checked where the pour and the exposed edge allow.
- Concrete cover at exposed edges — where reinforcement is visible after strip, cover is assessed against AS 3600 Concrete structures for the exposure classification, typically 30–40 mm for a residential slab on ground in SEQ.
- Slab classification correct for the site class — a waffle-pod, stiffened raft or footing system must suit the AS 2870 site class (M, H1, H2 or P). We confirm the system built matches the class the engineer designed to.
- Vapour barrier condition — the under-slab membrane and its turn-up at the edge, taped around penetrations, checked for tears per NCC 3.3.6.
- Termite barrier system — perimeter and penetration barriers installed to AS 3660.1 Termite management — new building work, collars intact at plumbing penetrations, joins lapped.
- Slab surface condition — checked for plane, shrinkage cracking, honeycombing and cold joints across the finished surface.
- Set-out against architectural drawings — overall dimensions and the position of the slab on the block checked against the approved plans.
- Service penetration locations — plumbing and electrical penetrations confirmed as correctly formed and positioned so later trades are not forced to re-core the slab.
- Falls to wet areas and drainage points — where the concreter has pre-formed set-downs and falls, they are checked against the plan.
Common slab defects and the standards they fail
The defects below are standards-based patterns, not site-specific claims. Any independent inspector working to AS 2870 and AS 3660.1 checks for the same items.
- Slab or edge-beam undershoot — a slab or edge beam built shallower than the engineer's detail reduces the section the design relies on to resist soil movement. AS 2870 sets the minimum footing and slab dimensions for each site class; an undershoot is a departure from the engineered design and is reported against the slab detail.
- Missing termite barrier collar at a plumbing penetration — AS 3660.1 requires a continuous barrier, including at penetrations. A collar that is torn, displaced or omitted when pipework was installed breaks the protected envelope and can void the termite management warranty.
- Vapour barrier torn at the edge beam — NCC 3.3.6 relies on a continuous under-slab membrane to control rising damp. A membrane torn at the edge turn-up during the steel fix leaves a path for moisture into the slab edge.
Why cover and dimensions are measured, not eyeballed
AS 3600 sets concrete cover by exposure classification because cover is what protects the reinforcement from moisture: too little, and the steel is exposed to corrosion over the life of the slab. AS 2870 sets slab and beam dimensions by site class because those dimensions are what let the slab bridge and resist the movement of reactive clay. Both are quantities the design depends on, so both are measured against the engineer's detail rather than assessed by eye — the report cites the clause and the drawing for each item, so the conversation with the builder is fact-based.
When to book: after the pour, before backfill
The slab inspection has a practical window. Too early and the concrete has not cured enough to walk and assess. Too late — after backfill, landscaping or the frame — and the slab edge, the membrane turn-up and the termite collars are buried and no longer inspectable.
The workable window is once the slab has cured enough to walk on and before the perimeter is backfilled, ideally before the frame is stood. Booking in that window means the full perimeter is still exposed and any item we flag can be addressed before it is permanently covered. We turn the report around the same day for most inspections, with photographs and clause references, so your site supervisor can act on it without delaying the frame.
Slab inspection vs pre-pour inspection
The two are sequential, not interchangeable. A pre-pour inspection happens before the concrete is placed, when the reinforcement, formwork and penetrations can still be moved. A slab inspection happens after the pour has cured and confirms what was actually delivered. The pre-pour is the higher-leverage check because nothing is set yet; the slab inspection is the record that the finished slab matches the design before the frame covers it. Owners building through the full sequence commonly book both, then continue to the frame inspection and eventually the practical completion inspection at handover.
Frequently asked questions
When should I book a slab inspection?
Book the slab inspection after the concrete has cured enough to walk on and before the frame is stood — usually a few days after the pour. Book it before backfill and landscaping cover the slab edge, because the edge beam, the vapour barrier turn-up and the termite barrier collars are only inspectable while the perimeter is still exposed.
How long does a slab inspection take?
A standard residential slab takes about an hour to an hour and a half on site, depending on the footprint and how much of the perimeter is still accessible. We measure the slab against the engineer's detail, photograph each item, and issue the report the same day for most inspections.
What happens if the slab inspection finds a defect?
Each item is documented with a photo, a location note and a reference to the clause it fails — AS 2870 for the slab and footing detail, AS 3660.1 for the termite management system, or the engineer's drawing. You forward the report to your site supervisor. Items found at slab stage are far cheaper to correct now than after the frame is up and the slab edge is buried.
Do I need to attend the slab inspection?
No. We coordinate access with the site supervisor and attend in hi-vis and safety boots. You receive the same-day PDF report with photographs and clause references, and we follow up by phone to walk you through anything flagged.
How does your slab report differ from the certifier's Form 16?
The building certifier issues a Form 16 to state that the slab stage complies with the approved documents for the purpose of the building approval. That is a statutory sign-off, not a defect list. Our inspection is an independent quality check against the Australian Standards and the engineer's drawings, written for you rather than for the approval file, and it records workmanship items a compliance sign-off does not itemise.
How is a slab inspection different from a pre-pour inspection?
A pre-pour inspection happens before the concrete is placed, while the reinforcement, formwork and penetrations can still be corrected. A slab inspection happens after the pour has cured, before the frame, and assesses the finished slab — surface condition, dimensions, cover where it can be seen, and the termite and vapour barrier systems at the edge. Many owners book both; the pre-pour catches what is about to be locked in, the slab confirms what was actually delivered.
How much does a slab inspection cost?
A standard residential slab inspection is $550 including GST across Brisbane and the Moreton Bay corridor. That covers the site attendance, the same-day photo-tagged report with AS 2870 and AS 3660.1 references, and a follow-up call. Larger or stepped-site slabs are quoted individually — call with the plan size and we will confirm before you book.
The slab is one stage in the build. See the pre-pour inspection that precedes it, the frame inspection that follows, or the full construction stage inspections journey through to handover.
What we check at the pre-pour stage
The slab and footing system is inspected before the pour — against the engineering, the soil classification and the approved working drawings. Our 100-point pre-pour checklist covers:
- Documentation & Approvals
- Site Preparation & Earthworks
- Setout & Dimensions
- Formwork
- Sand Bed & Vapour Membrane
- Termite Management (AS 3660.1)
- Beams, Trenches & Pod Systems
- Reinforcement — Mesh
- Reinforcement — Bars & Cages
- Services & Penetrations
- Pour Readiness & Quality Provisions
Confirm the Slab Before It's Buried
Book before backfill covers the slab edge
Book your slab inspection while the edge beam, membrane and termite barrier are still exposed.
Your build, stage by stage
Every new home moves through the same inspection sequence. See where this stage fits and jump to the ones before and after it.