A search for Australian apartment defect statistics returns a large number of percentages carrying no source attribution. Some are genuine figures separated from the qualifier that made them accurate. Others cannot be traced to any primary study, and appear to have been repeated between commercial websites until they acquired the appearance of established fact.

This article sets out what the published research reports, with citations, and the qualifiers that govern how each figure should be read.

The principal dataset

The most substantial Australian dataset is Johnston and Reid’s 2019 study for Deakin and Griffith Universities, which examined 3,227 individual defects recorded across 212 building audit reports in New South Wales, Victoria and Queensland.

The sampling basis governs the interpretation. These were buildings that had already been the subject of a defect audit, which is to say buildings where a party already suspected a problem. They are not a random sample of Australian apartment buildings. The dataset describes the population of audited buildings, in the same way that a study of hospital admissions describes illness rather than the health of the general population. Rates drawn from it will be higher than rates across the whole building stock, and the distribution of defect types is the more transferable finding.

On that basis:

Finding	Figure
Buildings with at least one defect across multiple locations (all states)	85%
Victorian buildings in the sample	47, constructed 2008–2017
Victorian buildings with defects across multiple locations	74%
Average recorded defects per Victorian building	11.7

The accurate Victorian statement is therefore: of 47 audited Victorian apartment buildings constructed between 2008 and 2017, 74% had defects appearing across multiple locations. A claim that 74% of Victorian apartments are defective omits the sample definition on which the figure depends.

Distribution of defects by system

The distribution is the more durable half of the study, because it is less sensitive to the sampling basis than the headline incidence rate.

By construction system, across all states:

Building fabric and cladding — 40%
Fire protection — 13%
Waterproofing — 11%
Roof and rainwater disposal — 9%
Structural — 7%

By cause and consequence, water ingress and moisture was the single most prevalent contributor, implicated in 29% of all recorded defects, ahead of safety issues (20%) and building damage (15%). Within the building fabric and cladding category specifically, water contributed to a third of defects.

The consequence of this distribution is that water is not one defect category among several; it is the mechanism operating beneath several of the others. Cladding systems fail when water penetrates behind them. Structural elements deteriorate when water and dissolved chlorides reach the reinforcement. Roof and rainwater disposal defects deliver water to elements not designed to receive it. The 11% recorded against waterproofing therefore represents defects in the waterproofing system itself, and understates the role of water across the dataset as a whole.

Waterproofing sub-categories and the Victorian pattern

Within waterproofing defects, the sub-categories ranked:

Balcony membranes — 28% (the largest)
Paint — 19%
Internal wet area membranes — 19%
Podium membranes — 10.5%
Window and door reveal membranes — 8.6%
Caulking seals — 7%
Planter boxes — 5%

The study recorded that Victoria reported a higher proportion of balcony membrane defects than the other states examined, alongside proportionally fewer internal wet area and paint defects.

For a Victorian owners corporation forecasting where remedial expenditure is likely to fall, balcony membranes and their associated details are the indicated starting point, on a documented and citable basis rather than an anecdotal one.

Victorian Government findings

Cladding Safety Victoria produced analysis of direct relevance to Victorian owners corporations, because its dataset was confined to Victorian buildings.

Analysing 359 buildings funded for combustible cladding rectification, CSV found that nearly half had defects unrelated to the cladding, comprising structural, fixing and sealing, or water ingress defects. Of the buildings with non-cladding defects, nearly 80% had water or moisture related structural damage.

The Strata Community Association (Vic) reported the related figure that, of 339 buildings in the program, one in four had leaking balconies, balustrades or terraces causing structural damage.

These findings carried a direct commercial consequence. Under the rectification program, owners were required to fix non-cladding defects at their own cost before cladding rectification proceeded. Buildings that had budgeted for a single scope encountered two scopes in sequence, with the second funded by a levy that had not been anticipated in any maintenance plan.

The contribution of design

Research cited in the same study attributes 50 to 60% of building defects to design issues, or holds that better design would have prevented them. The balance of 40 to 50% arises during construction.

The distinction determines the recovery pathway. A proportion of what presents on site as a workmanship defect originates in documentation: a junction that could not be built to function, a membrane termination with no defined upturn or drainage path, falls omitted from the drawings. The pathway against a design consultant differs from the pathway against a builder in limitation period, in the applicable duty and in the evidence required. Establishing which applies depends on identifying the mechanism of failure, which is an investigation task rather than a commercial one.

Victorian building stock and its age profile

Victoria has 128,896 registered owners corporation schemes covering over a million lots, and around 18% of Victorians live in strata. 57% of Victorian schemes were registered since 2000, against 50% nationally.

Victoria is therefore over-represented in the post-2000 apartment cohort. That stock is now twenty to twenty-five years old, which places it past the point at which original membranes, sealants, gaskets and applied coatings reach the end of a typical service life, and past any statutory warranty period.

The pattern is consistent with an ageing curve arriving on schedule across a large, comparatively young and geographically concentrated building stock, rather than with an isolated failure event. Because the timing is predictable from the age profile of the stock, it can be provided for through condition surveys and funded maintenance programmes in advance of the expenditure, rather than through levies struck after failure.

Figures excluded from this article

Several figures circulating in the sector could not be traced to a primary source, including a widely repeated claim about the proportion of new Melbourne apartments affected by defects. They are not reproduced here. Every figure on this site carries a citation, and where the sample size or jurisdiction affects the interpretation, that qualifier is stated alongside the figure.

Applying that test excludes some of the larger numbers in general circulation. The figures that remain are the ones for which the sample, the jurisdiction and the method can be checked by the reader against the published source.

Sources

Johnston, N. & Reid, S. (2019), An Examination of Building Defects in Residential Multi-owned Properties, Deakin University and Griffith University — hdl.handle.net/10072/414957
Cladding Safety Victoria, Research Analysis — Non-cladding Building Defects — vic.gov.au/other-building-defects
Strata Community Association (Vic), media release, 12 July 2023
Easthope, H., Lu, Y. & Rivera, A. (2025), Australasian Strata Insights 2024, City Futures Research Centre, UNSW Sydney

General information only. Figures are reported as published, with sample and jurisdiction stated. Condition assessment of an individual building requires inspection.

Victorian apartment defects: what the published research shows