Research from the Australian Building Codes Board estimates that defects are present in around 30–40% of new homes — and that the average cost of fixing a single significant issue is over $6,000. Many homeowners don’t discover these defects until months or years after handover, by which time their legal options may be limited.
Understanding the most common types of construction defects — what they look like, why they happen, and how to document them — is the first step to protecting your investment.
What counts as a building defect?
Under Australian Consumer Law (ACL) and state-based building legislation, a defect is broadly defined as work that:
- Falls below the standard a reasonable person would expect
- Doesn’t meet the requirements of the National Construction Code (NCC) or relevant Australian Standards
- Differs from what was agreed in your building contract
Defects are typically categorised as:
- Minor defects: Surface imperfections, cosmetic issues, or finishing work that doesn’t affect structural integrity or liveability. Examples: paint runs, tile lippage, scratched glass.
- Major defects: Issues that significantly affect the use or integrity of the building, or that are likely to worsen over time. Examples: waterproofing failures, structural cracking, non-compliant electrical work.
The distinction matters because different defect categories have different warranty periods and legal remedies.
The 10 most common new build defects
1. Waterproofing failures
Waterproofing is the single most common source of significant defects in Australian new builds. The problem is that it’s hidden — waterproofing is installed behind tiles and under floors, so failures often aren’t apparent until water has already penetrated.
Signs: Water stains on walls adjacent to wet areas, mould growth, tiles becoming loose or hollow, swelling of floor materials near bathrooms.
Why it happens: Incomplete application, insufficient curing time before tiling over the membrane, or using the wrong product in the wrong location.
Legal position: In most Australian states, waterproofing defects are classified as major defects with a 6–10 year warranty period.
2. Cracking — structural and cosmetic
Not all cracks are equal. Hairline cracking in plasterboard and render is very common and usually cosmetic. But wider cracking, diagonal cracking from door or window corners, or cracking that progresses over time can indicate structural movement.
Signs: Cracks wider than 2mm, step cracking in brickwork following mortar lines, cracks that are wider at one end (indicating differential settlement).
Why it happens: Foundation movement, inadequate reinforcement, excessive shrinkage in concrete, poor preparation of the soil substrate.
Legal position: Structural cracking is a major defect. Cosmetic cracking is typically addressed during the defects liability period.
3. Tile defects
Tiling defects are among the most common complaints in new builds. The most frequent issues are:
- Hollow tiles: Tiles that aren’t properly bedded, leaving air gaps underneath. They move underfoot and eventually crack or pop.
- Lippage: Adjacent tiles that aren’t flush, creating a trip hazard and an uneven appearance.
- Inconsistent grout: Wrong colour, missing grout, or joints of varying width.
- Cracked tiles: Usually from impact during construction or from tiles not having room to expand.
Why it happens: Rushing, incorrect adhesive, insufficient adhesive coverage (industry standard is 95% coverage for wet areas), or using internal tiles in external applications.
4. Plumbing defects
Plumbing defects range from minor nuisances to serious water damage. Common issues include:
- Leaking joints: Visible under sinks and behind toilets, or concealed in walls (detected via water meter test)
- Incorrect water pressure: Too high (causes noise and joint stress) or too low (frustrating to use)
- Slow drainage: Incorrect fall on drainage pipes
- Hot and cold transposition: Taps installed with hot and cold reversed
Legal position: Non-compliant plumbing is a major defect, and in most states plumbing work must be inspected and certified. Keep your compliance certificate.
5. Electrical defects
- Missing or non-compliant smoke alarms: Queensland requires interconnected photoelectric smoke alarms in all new homes since 2022. Standards vary by state.
- Incorrect circuit labelling: Switchboard not labelled per AS/NZS 3000
- Power points in wrong locations: Not matching electrical plan
- Light fittings not level or loose
All electrical work must be performed by a licensed electrician. Compliance certificates are mandatory.
6. Windows and doors that don’t operate correctly
Doors that bind, stick, or fail to latch are one of the most-reported issues in new builds. Windows that don’t close fully or seal properly can cause water ingress and energy loss.
Why it happens: Settling of the frame, incorrect installation, or wrong-sized door or window supplied.
7. Insulation defects
Insulation that’s missing, compressed, or incorrectly installed significantly affects energy performance. This is difficult to check without professional equipment or accessing the roof space.
What to check: Ask for the certificate of compliance for insulation. Check that the R-value specified in your contract matches what’s been installed.
8. External waterproofing and drainage
Poor site drainage causes water to pool against your foundation, increasing the risk of moisture penetration and foundation movement. Incorrectly installed flashings above windows and doors allow water to track into the wall cavity.
Signs: Efflorescence (white salt staining) on brickwork, damp internal walls, musty odour in lower levels.
9. Render and external cladding defects
- Cracking in render: Fine crazing is common and usually cosmetic. Wider cracks that allow water ingress are more serious.
- Delamination: Render pulling away from the substrate
- Cladding gaps: Incorrect or missing jointing between panels, particularly concerning for fire spread in multi-story buildings
10. Roofing defects
- Missing or cracked tiles
- Incorrect fall (water pools on the roof)
- Flashings not correctly sealed around penetrations (skylights, solar systems, vents)
- Inadequate sarking under roof tiles
How to document defects effectively
The difference between a resolved defect and an unresolved one often comes down to documentation. Builders are far more likely to action a clear, specific defect report than a vague verbal complaint.
When logging a defect:
- Photograph it clearly. Multiple angles if possible. Include a coin or ruler for scale if the defect size matters.
- Describe it specifically. “Cracked tile in main bathroom, second tile from left in row adjacent to shower screen” is more useful than “broken tile in bathroom.”
- Note when you discovered it. This matters for warranty purposes.
- Categorise the severity. Minor (cosmetic), major (functional impact), or critical (safety or structural).
Checka is designed to make this process fast — photograph, describe, tag the location, and Checka helps categorise severity. Your entire defects log is available as a professional report at any time.
Your warranty rights in Australia
| Defect type | Typical warranty period |
|---|---|
| Defects liability period (general) | 13 weeks – 12 months (varies by state and contract) |
| Major defects (structural, waterproofing) | 6 years (NSW, VIC) to 10 years (QLD) |
| Non-structural major defects | 2 years (VIC) to 6 years (other states) |
Always check your specific state’s legislation, as periods vary. Your building contract must also disclose the applicable warranty terms.
Key Takeaways
- Around 1 in 3 Australian new homes has at least one major defect — inspecting thoroughly at handover is essential
- Waterproofing failures are the most common major defect and the hardest to detect once tiling is complete
- Minor and major defects have different warranty periods — know the difference
- Document every defect with photos, descriptions, and dates from the moment you discover them
- A professional building inspector at your handover inspection dramatically reduces the chance of missing significant issues
- Checka provides a timestamped, photo-backed defects record that’s ready for your builder, certifier, or tribunal
Free to download
Stop losing track of defects.
Checka helps you capture issues, stay organised, and arrive at handover with a complete record of your build.