At each construction stage in Australia, specific defects require immediate attention before the build progresses. Slab stage issues include incorrect concrete placement and missing moisture barriers. Frame stage defects involve structural timber problems, incorrect tie-down connections, and out-of-plumb walls. Lock-up stage concerns waterproofing failures and window installation errors. Pre-handover defects range from poor finishes to incomplete work. Under Australian building contracts, builders must rectify defects before progressing, as subsequent stages often conceal earlier problems permanently.
This guide is written for anyone building a new home in Australia, whether through a volume builder or custom construction. Stage inspections are your opportunity to catch defects while they are still visible and fixable. Once concrete is poured over reinforcement or plasterboard covers framing, rectification becomes exponentially more expensive, sometimes impossible without demolition.
Australian building contracts typically include clauses requiring defect rectification before stage payments. The National Construction Code and relevant Australian Standards set minimum requirements, but your independent inspector should verify compliance at each milestone.
47%
New homes with major defects
$27,000
Average rectification cost
5
Recommended stage inspections
Understanding Construction Stages in Australia
Australian residential construction follows a predictable sequence of stages, each with corresponding progress payments. Understanding these stages helps you know when to book new construction stage inspections and what issues to prioritise.
| Stage | Payment (typical) | Key Focus Areas |
|---|---|---|
| Base/Slab | 15-20% | Foundations, moisture barriers, concrete |
| Frame | 20-25% | Structural timber, bracing, tie-downs |
| Lock-Up | 20-25% | Roof, windows, external cladding |
| Fixing/Fit-Off | 15-20% | Internal linings, wet areas, services |
| Practical Completion | 5-10% | Finishes, functionality, compliance |
Critical Timing
Book your independent inspection before signing off on each stage payment. Once you pay, you lose significant leverage for rectification.
Slab Stage Critical Defects
The slab stage inspection occurs after concrete curing but before frame construction begins. This is your only opportunity to identify foundation issues that will be permanently hidden.
Defects to Identify
- Correct slab dimensions matching approved plans
- Adequate concrete cover over reinforcement
- Moisture barrier installation and overlap sealing
- Termite management system correctly installed
- Service penetrations properly sleeved
- Level tolerance within NCC requirements
Common slab defects include honeycombing (air pockets in concrete), incorrect slab thickness, exposed reinforcement, and damaged moisture barriers. Cracks exceeding 0.3mm width may indicate structural issues requiring engineering assessment.
Hidden Danger
Termite management systems installed at slab stage are frequently compromised during construction. If barriers are damaged and not repaired, your warranty may be void.
Frame Stage Structural Concerns
Frame stage is arguably the most important inspection point. Structural framing will be concealed by cladding and plasterboard, making future assessment difficult and rectification expensive.
Critical Frame Defects
| Defect Type | Severity | Rectification Difficulty |
|---|---|---|
| Missing tie-down connections | Major | Moderate before lining |
| Out-of-plumb walls (>5mm/2.4m) | Major | Difficult after lining |
| Undersized or incorrect timber grades | Major | Very difficult |
| Inadequate bracing | Major | Moderate before lining |
| Incorrect truss installation | Major | Expensive |
| Missing noggins at sheet joins | Minor | Easy before lining |
- Twisted or bowed studs affecting wall straightness
- Incorrect spacing of structural members
- Missing or inadequate fire separation framing
- Unapproved modifications to engineered designs
Frame stage inspections should verify compliance with the engineer's design and AS 1684 (Residential timber-framed construction). Connection details, including nail patterns and connector plates, must match specifications.
Lock-Up Stage Weatherproofing Issues
Lock-up stage means the building is enclosed with roof complete, external cladding installed, and windows and doors fitted. Water penetration risks become the primary concern.
Weatherproofing Checklist
Roof Assessment
Check tile or metal installation, flashings at penetrations, valley and ridge cappings, and gutter fall.
Window and Door Installation
Verify head flashings, sill drainage, weatherstripping, and sealant application.
External Cladding
Inspect joints, control joints, clearances to ground, and cavity drainage.
Window installation errors are among the most common lock-up defects. Missing head flashings or incorrect sealant application can allow water ingress that damages framing and promotes mould growth. These issues may not manifest for years but cause significant damage.
If you discover weatherproofing defects, a defect investigation report can document the issues formally for dispute resolution.
Practical Completion Final Defects
Practical completion, also called pre-handover, is your final opportunity to identify defects before taking possession. At this stage, defects tend to be cosmetic, but functional and compliance issues must also be checked.
- Practical Completion
The point at which construction is substantially complete and the dwelling is fit for occupation, though minor defects may remain.
- Defects Liability Period
A contractual period (typically 13 weeks to 6 months) during which the builder must rectify defects identified after handover.
Common Pre-Handover Defects
| Category | Examples | Typical Count per Home |
|---|---|---|
| Paint finishes | Runs, missed areas, poor cut-in | 15-30 items |
| Joinery | Gaps, poor alignment, scratches | 10-20 items |
| Wet areas | Grout voids, silicone quality, waterproofing certificate | 5-15 items |
| Flooring | Tile lippage, carpet stretching, timber gaps | 5-10 items |
| Functionality | Doors, windows, fixtures operation | 5-15 items |
Booking a pre-handover inspection ensures comprehensive documentation of all defects, giving you leverage to ensure rectification before final payment.
Ensuring Defects Are Fixed Before Progression
The question of whether defects were fixed before the build progressed is fundamental to quality construction. Your building contract should specify defect rectification requirements.
Pros
- Written defect lists create accountability
- Photographic evidence supports future claims
- Stage payments provide rectification leverage
- Independent inspections provide objective assessment
Cons
- Verbal agreements are difficult to enforce
- Signing off without inspection loses leverage
- Relying solely on certifier inspections misses defects
Documentation Practice
Create a formal defect register with photographs, dates, and builder responses. Email communication creates a paper trail that may prove valuable if disputes arise.
Frequently Asked Questions
QHow many stage inspections should I get during construction?
Most building professionals recommend five stage inspections: pre-slab, frame, lock-up, fixing/waterproofing, and practical completion.
Some owners add additional inspections at critical points such as pre-pour (checking reinforcement before concrete) or post-waterproofing (before tiling covers wet area membranes). The number may increase for complex or multi-storey builds. Each inspection costs between $300 and $500 depending on the stage and property size.
QWhat happens if defects are not fixed before the next stage?
Defects covered by subsequent work become exponentially more expensive to rectify and may void warranties if concealed without repair.
Your building contract typically requires you to approve each stage before the builder proceeds. If you sign off on a stage knowing defects exist, you may be deemed to have accepted them. Document all defects in writing and withhold stage payment approval until critical items are rectified. For disputes, contact your state building authority for guidance.
QAre frame stage defects the most important to catch?
Frame stage defects are among the most significant because structural framing becomes permanently concealed by cladding and internal linings.
While every stage matters, frame stage issues like incorrect tie-downs, undersized timbers, or inadequate bracing affect the structural integrity of the entire building. Rectification after plasterboard installation may require significant demolition and reconstruction. Pre-slab inspections are equally important for foundations.
QCan I withhold payment if defects are not fixed?
You can withhold payment proportionate to the value of defective work, but you cannot withhold entire stage payments for minor defects.
Australian building contracts and consumer protection laws generally allow withholding payment for uncompleted or defective work. However, withholding disproportionate amounts may constitute breach of contract. Document defects thoroughly and communicate in writing. For significant disputes, seek legal advice or contact your state tribunal (NCAT in NSW, VCAT in Victoria, QCAT in Queensland).
QWhat is the NCC tolerance for slab level?
The NCC references AS 2870 which allows a maximum deviation of ±15mm for domestic slabs, with tighter tolerances for floor coverings.
For concrete slabs receiving floor coverings, the maximum deviation is typically ±5mm in 3 metres for tiles and ±3mm in 3 metres for vinyl or timber. Slabs outside these tolerances require levelling compounds or grinding before floor finishes can be installed, adding cost and potentially voiding warranties if not disclosed.
QShould the building certifier catch all defects?
Building certifiers verify code compliance at specific inspection points but do not perform comprehensive quality inspections.
Certifier inspections are mandatory for occupancy certificates but focus on compliance with approved plans and building codes. They typically spend limited time on site and may not identify quality issues, workmanship defects, or items that meet minimum code but fall below reasonable standards. Independent inspections complement certifier reviews by focusing on quality and contractual compliance.
QHow long do I have to report defects after handover?
The defects liability period is typically 13 weeks under most building contracts, with structural defects covered by statutory warranties for 6 years.
During the defects liability period, builders must rectify defects at no cost. After this period, statutory warranties still apply: 6 years for structural defects and 2 years for non-structural defects in most states. Report defects in writing as soon as discovered, regardless of the warranty period.
QWhat defects are most commonly missed without independent inspection?
Frame tie-down connections, waterproofing membrane installation, and termite barrier continuity are frequently missed without independent inspection.
These items are concealed by subsequent work and may not manifest as problems for years. When they do fail, rectification is expensive. Other commonly missed items include incorrect window head flashings, inadequate roof sarking overlaps, and missing fire collar installations around services.
QCan I attend stage inspections myself?
Yes, owners can and should attend stage inspections, though professional expertise is needed to identify many defects.
Attending inspections allows you to understand issues firsthand and ask questions. However, identifying structural defects, code compliance issues, and workmanship problems requires professional training and experience. Consider attending alongside your independent inspector to maximise learning while ensuring nothing is missed.
QWhat documentation should I receive at each stage?
You should receive engineer's certificates, waterproofing certificates, termite treatment certificates, and certifier inspection reports at relevant stages.
Keep copies of all certificates, inspection reports, approved plans, variations, and written correspondence. These documents may be required for future insurance claims, warranty disputes, or property sale. Some certificates like waterproofing and termite treatment are required for the final occupancy certificate.
Key Takeaways
- Each construction stage has specific defects that become hidden and expensive to fix once subsequent work progresses
- Slab stage requires verification of moisture barriers, termite systems, and concrete quality before framing begins
- Frame stage is critical for structural integrity with tie-downs, bracing, and timber grades checked before concealment
- Lock-up stage focuses on weatherproofing including roof flashings, window installation, and external cladding
- Practical completion covers finishes, functionality, and final compliance before handover
- Document all defects in writing with photographs before signing stage payment approvals
- Independent inspections complement but do not replace mandatory certifier inspections
- Statutory warranties provide 6 years coverage for structural defects and 2 years for non-structural issues
References and Resources
- National Construction Code
- Australian Standard AS 4349.0 Inspection of buildings
- Australian Standard AS 1684 Residential timber-framed construction
- NSW Fair Trading - Building and renovating
- Queensland Building and Construction Commission
- Victorian Building Authority
- Australian Standard AS 2870 Residential slabs and footings
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