LEARN:

Post-completion defects are faults in a building that surface after it's been handed over. They cover a wide range of issues, from a tile that drums when tapped, to a wall that cracks two summers after move-in, to a balcony that fails its waterproofing on the first heavy rain.

This article walks through the categories, the common causes, what an owner or builder typically does about them, and where independent investigation fits in.

What counts as a post-completion defect

Most state legislation and most building contracts define a defect broadly: work that doesn't meet the contract, the relevant Australian Standards, or the National Construction Code. Within that broad definition, the practical categories are:

• Structural defects. Issues affecting the structural integrity of the building. Cracking in slabs, sagging beams, undersized members, missing tie-downs, foundation settlement.
• Waterproofing failures. Membrane failures in bathrooms, balconies, planter boxes, and basements. Water ingress through external walls, roofs, gutters, and penetrations.
• Fire and acoustic separation. Failures in fire-rated walls, doors, and penetrations. Acoustic separation issues in multi-residential.
• Finishes defects. Tile lippage and cracking, render failure, paint failure, cabinetry issues, lining defects.
• Building services. Plumbing leaks, electrical faults, mechanical (HVAC) failures, hydraulic issues.
• Workmanship. General poor workmanship that doesn't fit a specific category but doesn't meet the tradesmanlike standard expected.

The category usually drives which trade is involved and which Australian Standard applies.

How post-completion defects arise

Three common causes:

• Construction error. The work wasn't done to specification. The trade misread the drawings, used the wrong materials, or didn't follow the installation instructions.
• Design failure. The specification itself wasn't fit for purpose. The design didn't account for the actual loads, exposures, or use the building would see.
• Latent material defect. The materials installed were defective from the manufacturer. The defect didn't show up at install but emerged later.

Often the cause is a combination. A waterproofing failure might come from a marginal design (membrane specification thin for the exposure) combined with a construction error (incomplete laps at penetrations).

Establishing which combination of causes is at play is the work of a forensic investigation.

The pattern of how defects surface

Post-completion defects rarely show up evenly through the warranty period. The common pattern:

• First few months. Workmanship defects that became obvious once finishes were complete and the property was occupied. Cosmetic issues, lining defects, paint touch-ups, minor cracking.
• First winter or first heavy rain event. Waterproofing failures, drainage issues, roof leaks, balcony water ingress. These wait for weather to expose them.
• Six to eighteen months. Settlement-related cracking, render failure, joinery issues that emerged once the building had been through a thermal cycle.
• Two to five years. More serious structural movement, accumulated waterproofing failures, latent material defects. This is where the major rectifications usually live.

Knowing where in the curve a property sits helps frame the investigation.

What an owner should do

A pragmatic sequence:

1. Notify the builder in writing. Specify the defect and date.
2. Take dated photographs. Especially for defects that change with weather or use.
3. Don't rectify yourself. Owner-attempted rectification can obscure cause and complicate later claims.
4. Engage an independent investigation if disputed. A forensic investigation establishes cause, attributes responsibility, and provides the evidence base for further action.
5. Track the statutory warranty period. Different states have different periods for structural and non-structural defects; the clock starts at completion.

What a builder should do

For builders responding to a defect notification:

1. Acknowledge in writing. Most state legislation requires a response inside a defined period.
2. Inspect promptly. Early inspection costs less than late inspection.
3. Distinguish workmanship from design. Where the cause sits in the design, the builder's responsibility differs from the case where the cause is construction error.
4. Don't dispute without evidence. Disputing a defect that turns out to be valid increases the eventual cost of rectification and damages the builder's reputation.
5. Engage independent investigation if the cause is contested. An independent investigation often resolves the matter without a tribunal.

Where independent investigation fits

A forensic building inspection cuts through the dispute. The investigator works from the contract, the design documents, and the physical evidence on site. The output is a written report that names the defect, evidences the cause, and addresses responsibility.

For owners, the report is the foundation of any claim. For builders, the report often establishes that the cause sits elsewhere (design failure, owner maintenance, third-party damage) and reduces the builder's exposure. For lawyers, the report is the evidence base for a tribunal or court matter.

QBFS conducts post-completion defect investigations across Australia.

Call Paul on 0407 146 737.

Start With a Call

Best way to start is a phone call. Tell Paul the project, the issue, where you sit in the build cycle. The next step gets sorted on the call: site visit, desktop review, or a referral if QBFS isn't the right fit.