Most common building defects in residential multi-owned properties

In a recent research paper pertaining to the examination of building defects in residential multi owned properties, there has been some great findings. These findings were authored by Nicole Johnston (Deakin University) and with Sacha Reid (Griffith University).
In summary, two studies have been undertaken to identify the most common building defects in residential multi-owned properties. The studies were both conducted by the same group of researchers (Easthope, Randolph and Judd).
The first study conducted in 2009 found that the most common defects identified by lot owners were water ingress, internal and external wall cracking, roofing and guttering problems and tiling faults.
In 2012, anchored off the original study, the researchers surveyed a larger owner cohort where respondents identified water leaks (42%), internal and external wall cracking (42%), exterior water penetration (40%), guttering problems (25%), defective roof coverings (23%), plumbing faults (22%), and tiling related defects (20%).

In the interest of endeavouring to find out why these defects are ever present; attempts have been made by the researchers to identify the stages (in development) in which defects arise.
Interestingly, and of a surprise to me, the study showed that 50% to 60% of building defects are attributed to design issues and would have been preventable with better design. Therefore, concluding that some 40% to 50% of defects arise in the construction phase.
Furthermore, of the percentage of defects that were attributed to the findings, some 32% originated in the earlier phases of development (including design), approximately 45% originated on site and remaining approximate 20% related to materials and machines.
It appears that data was collated from various building consultants and auditing companies, with the breakup of theses providers noted as follows; some 99 x report providers from NSW, 66 x report providers from QLD and 47 x report providers from VIC.
Similarly, an additional method of further drilling down to gain a deeper understanding of the prevalence of these defects was to interview these stakeholders. With some 21 interviews conducted across the 3 states, with a guide provided to them with the questions based on review of the literature. Of these 21 interviewees, lawyers and committee members made up 12.
In the process of the data collection, and by a way of summarising the findings, it was noted that many of the interviewees suggested that human error played a significant part in the building defects. This human error was largely summarised as misuse of building products (due to lack of knowledge), poor workmanship, time pressures (cutting corners), poor supervision, lack of training, lack of licensing and trade accountability.

Having noted this, further observations (mainly two recurring observations) were made by the interviewees regarding organisations factors that contributed to building defects and the prevalence of the building defects. The first recurring observation was the motivation to make a profit and the second was time pressures that resulted in mismanaged process time allocation and co-ordination of trades.
When questioning surrounding the use of Private Certifiers was raised and if Private certification systems were flawed, the general consensus of the 12 x lawyers and committee members was that the system was deeply flawed, with committee members raising more pointed concerns that the private certifying system was not only conflicted in their interests but their documents were at times fraudulent.
In what I found to be staggering, one of the interviewees, a private certifier, noted that “it is not feasible to inspect every element of the building either before or after construction”. With the certifier adding “Responsibility must be on all those involved in the building process”.