The 6 Mandatory Building Inspections in NSW: What Happens at Each Stage

Every residential build in NSW requires six mandatory critical stage inspections conducted by the Principal Certifier (PC). These inspections are your main line of defence against building defects, and they’re required by law under the EP&A (Development Certification and Fire Safety) Regulation 2021, Section 61. Here’s what happens at each stage, what the certifier is looking for, and why each inspection matters.

Why are building inspections required in NSW?

Building defects cost NSW homeowners an estimated $700 million per year. The mandatory inspection regime exists to catch compliance issues during construction, when they can be corrected cheaply and easily. Once a stage of work is covered by the next stage (concrete poured over reinforcement, tiles laid over waterproofing, soil backfilled over drainage), the only way to check it is destructive investigation, which is expensive and disruptive.

The six inspections are strategically timed at the points in construction where critical work is about to be permanently concealed. Each one represents the last opportunity to verify compliance before that stage of work is hidden from view.

Inspection 1: After excavation, before footings – what does the certifier check?

This inspection occurs after the site has been excavated for the footings but before any concrete is poured. The certifier inspects:

Soil conditions. The certifier verifies that the actual soil conditions on site match what was assumed in the geotechnical report and engineering design. In areas with reactive soil (common in parts of Western Sydney), this is critical. If the soil classification is different from what was assumed, the footing design may need to be adjusted.

Excavation depth and dimensions. Confirms the excavation matches the engineering plans for depth, width, and location.

Site drainage. Checks that the excavation is not sitting in water and that temporary drainage is adequate.

Why it matters: The footings are the foundation of the entire building. Errors at this stage affect everything built above. Houses built on foundations that don’t match the soil conditions can experience structural cracking, uneven settling, and in severe cases, sinking. Rectification at this stage is minor. Rectification after the house is built requires underpinning, which can cost $20,000 to $100,000+.

Inspection 2: Before pouring reinforced concrete – what is checked?

This inspection takes place after the reinforcement (steel bars and mesh) has been placed in the formwork but before the concrete is poured. The certifier checks:

Reinforcement placement. Verifies that the size, spacing, and positioning of reinforcement bars match the structural engineer’s specifications. This includes checking bar diameters, lap lengths, cover to formwork, and tie wire connections.

Formwork dimensions. Confirms the formwork (moulds for the concrete) is the correct size and shape as per the engineering drawings.

Chairs and spacers. Checks that reinforcement is properly supported to maintain the specified cover (distance between the steel and the surface of the concrete). Insufficient cover can lead to corrosion of the reinforcement over time.

Why it matters: Once concrete is poured, the reinforcement is permanently hidden. If bars are the wrong size, incorrectly spaced, or sitting on the bottom of the formwork without proper cover, the structural integrity of the slab or footing is compromised. This is not something that can be fixed after the pour. It can only be verified before.

Inspection 3: Before covering framework – what does this involve?

This inspection covers the structural framework of the building: floor framing, wall framing, and roof framing. It occurs after the frame is erected but before it’s enclosed by cladding, linings, or insulation. The certifier checks:

Framing compliance. Verifies that the timber or steel framing matches the engineering plans and complies with the relevant Australian Standards (such as AS 1684 for timber framing). This includes checking member sizes, spacing, connections, bracing, and tie-downs.

Structural connections. Checks that load paths are continuous from roof to foundations, with appropriate brackets, straps, and fixings at each connection point.

Openings and lintels. Confirms that openings for windows and doors have correctly sized lintels and are properly supported.

Bracing. Verifies that wall bracing meets the engineering requirements for wind and earthquake loads.

Why it matters: The frame is the skeleton of the building. Once it’s covered by cladding, plasterboard, and insulation, it’s impossible to inspect without removing those materials. Framing defects can lead to cracking, bowing walls, sagging roofs, and in extreme cases, structural failure. This is also the stage where missing or inadequate bracing is identified.

Inspection 4: Before covering waterproofing – why is this so important?

This inspection verifies that waterproofing in wet areas (bathrooms, laundries, showers, balconies) has been correctly applied before tiling or other finishes cover it. The certifier checks:

Waterproofing membrane. Confirms that the waterproofing membrane is continuous, with no gaps, tears, or missed areas. Checks that the membrane extends to the correct height on walls (generally 150mm on floor areas, 1800mm in shower areas) and that all penetrations (pipes, drains) are properly sealed.

Number of coats. Verifies that the minimum number of waterproofing coats has been applied. The Building Code requires at least two coats. Industry best practice is three coats, which provides an additional layer of protection.

Drying and curing. Checks that each coat has been properly cured before the next was applied and before tiling begins.

Why it matters: Waterproofing failures are one of the most common and costly building defects. Once tiles are laid over the membrane, the waterproofing is completely hidden. Failures typically don’t appear for months or even years, when water starts leaking through to hallways, lower levels, or neighbouring units. Rectification requires removing all tiles, stripping the waterproofing, reapplying it, and retiling. Cost: $10,000 to $50,000+ per wet area. This is the inspection where in-person attendance by the certifier is most critical. Photos simply cannot show what an experienced certifier can identify by walking the space.

Inspection 5: Before covering stormwater drainage – what is verified?

This inspection occurs after stormwater drainage connections have been installed but before they’re backfilled or otherwise concealed. The certifier checks:

Pipe sizes and grades. Confirms that stormwater pipes are the correct diameter and installed at the correct fall (gradient) to ensure water flows away from the building as designed.

Connection points. Verifies that connections to the council stormwater system, on-site detention tanks, or absorption trenches are correctly installed and match the approved stormwater management plan.

Joint integrity. Checks that pipe joints are properly sealed to prevent leaks and root intrusion.

Why it matters: Once drainage is buried, it’s expensive to access and repair. Incorrect drainage can cause water pooling around the foundation (leading to structural movement), flooding of the site or neighbouring properties, and erosion. Council takes stormwater compliance seriously, and non-compliant drainage can also result in enforcement action.

Inspection 6: The final inspection – what happens before the Occupation Certificate?

The final critical stage inspection is the most comprehensive. It occurs after all building work is complete and before the Occupation Certificate (OC) is issued. This inspection must be conducted by the Principal Certifier personally; it cannot be delegated. The certifier reviews:

Overall compliance. A walk-through of the completed building to verify it matches the approved plans and complies with the National Construction Code.

Safety and amenity. Checks that smoke alarms are installed, safety glazing is in place where required, balustrades meet height and spacing requirements, and all safety features are compliant.

Documentation review. Confirms that all required certificates and compliance documents have been received: engineering completion certificates, plumbing certificates, waterproofing certificates, electrical certificates, and any other trade-specific documentation.

Conditions of consent. Verifies that any conditions attached to the CDC or development consent have been satisfied.

Why it matters: The final inspection is the last check before the building is certified for occupation. It’s the certifier’s confirmation that the completed building is safe, compliant, and suitable for people to live or work in. The OC is required before the building can be legally occupied.

What happens if work fails an inspection?

If the certifier identifies non-compliant work at any inspection stage, they will direct the builder to rectify the issue. Building work cannot proceed to the next stage until the problem is fixed and passes a re-inspection.

Common reasons for inspection failures include reinforcement that doesn’t match the engineering specifications, waterproofing that hasn’t been applied to the correct height or number of coats, framing connections that don’t match the bracing plan, and drainage installed at the wrong fall.

A failed inspection is not a disaster. It means the system is working as intended: the issue has been caught while it’s still easy and cheap to fix. The short delay and cost of rectification during construction is nothing compared to the cost of fixing the same problem after the building is complete.

Frequently asked questions

How many mandatory building inspections are there in NSW?

Six. They cover excavation/footings, reinforced concrete, framework, waterproofing, stormwater drainage, and a final inspection. These are set out in the EP&A Regulation 2021, Section 61.

Who conducts the mandatory building inspections?

Your appointed Principal Certifier (PC), which can be a private accredited certifier or council. The final inspection must be conducted by the PC personally.

What happens if my build fails an inspection?

The builder must rectify the non-compliant work before proceeding. A re-inspection is conducted after the fix. This is the system working as intended: catching issues when they’re cheap to fix.

Can a builder proceed without passing an inspection?

No. Builders must notify the PC and allow the inspection before covering work. Covering work before inspection is a serious compliance breach and the certifier may require it to be uncovered.

Are additional inspections beyond the six mandatory stages required?

The six are the minimum. A thorough PC may schedule additional inspections for complex projects, challenging sites, or where earlier inspections have identified concerns.

Key takeaways

• Six mandatory critical stage inspections are required for residential builds in NSW, timed at points where work is about to be permanently concealed.
• Each inspection checks that the work complies with engineering specifications and the National Construction Code before it’s covered by the next stage.
• Waterproofing (Inspection 4) is one of the most critical, as failures are hidden by tiling and can cost $10,000 to $50,000+ to fix.
• The final inspection must be conducted by the Principal Certifier personally and is required before the Occupation Certificate can be issued.
• In-person inspections provide significantly better compliance oversight than photo-based approaches.
• A failed inspection is the system working. Catching an issue during construction is always cheaper than fixing it after completion.