Australian Standards We Inspect Against

AS 2870 governs how the slab and footings under a house are designed and built for the soil they sit on. It sets out how reactive (clay) soils are classified — from Class A through to Class E and P — and matches each class to a slab type, reinforcement layout, footing depth and edge-beam thickening. At inspection it matters because a slab designed for the wrong site classification, or built with reinforcement in the wrong position, can crack, heave or settle long after handover when the soil moves.

AS 3600 is the engineering standard for concrete design and construction, covering concrete strength, reinforcement cover, bar spacing and curing. In a new home it underpins the slab, any suspended floors, and concrete elements the structural engineer has specified. At inspection it matters because reinforcement that sits too close to the surface, or concrete placed without adequate cover, loses durability and structural capacity — problems that are invisible once the pour is complete, which is why the pre-pour check is critical.

AS 1684 is the standard for designing and building timber-framed walls, floors and roofs in homes. It specifies member sizes, stud and joist spacing, bracing, tie-down and fixing requirements based on wind classification, along with tolerances for plumb and straightness. At frame stage it is the primary reference for checking that the structure carrying the house is sized, braced and tied down correctly — because most framing is hidden behind plasterboard once lining begins, the frame inspection is the last practical chance to verify it.

AS 4773 (with AS 3700 for engineered masonry) governs brick and block construction in homes, covering mortar, articulation joints, wall ties, damp-proof courses and weep holes. At inspection it matters because masonry that lacks articulation joints in reactive-soil areas, or that has blocked or missing weep holes, can crack and trap moisture inside the cavity — issues that show up as cracking and damp staining months or years after the build is finished.

AS 3740 sets out how bathrooms, ensuites, laundries and other wet areas must be waterproofed, including membrane coverage, upturns at walls and thresholds, treatment of penetrations, and falls to the floor waste. At inspection it matters because waterproofing failures are among the most common and most expensive defects in new homes — once tiling goes over a faulty membrane the only fix is to strip and redo the area, so the waterproofing inspection before tiling is the cost-effective point to catch it.

AS/NZS 3500 is the standard for plumbing and drainage, covering water supply, sanitary plumbing, stormwater and drainage installation. In a new home it governs pipe sizing, falls on drains, venting, fixture connections and stormwater discharge. At inspection it matters because drainage with insufficient fall or incorrect connections leads to slow drainage, blockages and water pooling — and because much of the drainage is laid before the slab is poured, the pre-pour and slab stages are key points to confirm it is correct.

AS 1668 covers mechanical ventilation and air handling, including the exhaust ventilation required for wet areas such as bathrooms and laundries that do not have adequate natural ventilation. At inspection it matters because inadequate or unducted exhaust fans leave moisture inside the home, which over time causes condensation, mould and damage to linings and finishes — a defect that is easy to verify at the final inspection but commonly overlooked.

The National Construction Code is the overarching regulatory document for building work in Australia, with Volume 2 covering Class 1 and Class 10 buildings — that is, detached houses and structures like garages, sheds and carports. It sets the legal minimum for structure, weatherproofing, fire safety, health and amenity, and energy efficiency, and it references the Australian Standards for the technical detail. At inspection it matters because a defect that breaches the NCC is non-compliant with the law, and the certifier should not issue final compliance until it is rectified.