Examining moisture related disputes in Victorian residential buildings

What we did and why

Water ingress and moisture damage routinely tops the list of issues in complaints to the BPC, claims to the Victorian Managed Insurance Authority (VMIA) and disputes to disputes resolution services. Water proofing and drainage issues are commonly occurring areas of compliance risk the BPC identifies through the Proactive Inspections Program and Plumbing Audit Program.

The BPC partnered with DBDRV and RIC Solutions (previously Restoration Industry Consultants) (RIC) to undertake research that expands the evidence base about moisture ingress and indoor mould in Victorian residential buildings by including insights from analysis of applications to DBDRV for dispute resolution.

Led by Dr Tim Law from RIC, the research aimed to:

• Quantify the nature and extent of moisture ingress and indoor mould in Victorian residential buildings based on applications to DBDRV for dispute resolution.
• Identify the causes and underlying factors contributing to the moisture ingress and indoor mould, and whether these are consistent with the findings of the scoping study.
• Identify potential practitioner competency gaps, and opportunities to strengthen consumer protection through targeted regulatory interventions or reform to reduce the cause of moisture ingress and indoor mould.

This research follows the Scoping study on the nature and extent of moisture damage in houses and apartments in Victoria by Victoria University. The scoping study was developed around a limited dataset of buildings that had been insured and claimed under the DBI scheme, and which was not representative of all residential buildings in Victoria.

Expanding the evidence base through this project to include analysis of disputes to DBDRV aimed to provide broader insights into the extent, causes and opportunities to address moisture ingress and indoor mould in Victorian residential buildings.

What we found

This study examined 6,299 de-identified residential building disputes (containing 96,803 individual issues) submitted to DBDRV from July 2018 to June 2023. These disputes were then overlaid with BPC data about building surveyors, builders and building permits.

From these, 49 water-related domestic building disputes that were identified as being representative of the broader dataset were adopted as case studies in this research.

A desktop review of de-identified Domestic Building Assessment Reports, including photographs and associated documentation (e.g., building/occupancy permits, building contracts, architectural and structural engineering drawings, third party inspection reports, etc) provided by DBDRV was undertaken to identify patterns and clusters of problematic building work that are likely to result in moisture damage. From this, likely causes, and opportunities to reduce the likelihood of this problematic building work occurring were identified.

There are limitations to this research and caution should be taken in extrapolation of results:

• despite the DBDRV dataset (n=6,299) being one of the largest datasets of building faults available to Victoria, it is still comparatively small to the number of building permit numbers issued annually by the BPC (approximately 87,000 permits for domestic and residential buildings in financial year 2022-23)
• only items that are the subject of the dispute are assessed in line with the current remit of DBDRV
• desktop reviews of documentation for case studies were limited to information and associated documentation held by DBDRV, and
• determining the extent to which the observations are representative of the broader built environment, is beyond the scope of this study.

The research made various findings from the analysis of the 6299 disputes and 49 case studies:

• The local government areas with the highest dispute rate (number of disputes per 100 building permits) tended to be along Melbourne’s growth corridors.
• Nearly thirty one percent of the individual dispute items were identified as water-related when assessed against the researcher’s compiled lexicon of water-related terms.
• Notable issues from the case studies were moisture accumulation from a lack of site drainage, non-compliant roofing or roof plumbing, wet walls in basement car parks, moisture ingress on balconies and from waffle raft slabs, and leaks from internal wet areas.
• Where building or occupancy permits were available, there were no performance solutions documented that related to internal/external waterproofing, roof plumbing or site drainage.
• In bathrooms, the absence of a waterstop was most the most frequently noted issue. Waterproofing membrane failures were less frequent, perhaps due to the requirement of more specialised equipment or more invasive or destructive testing methods.
• While access to roofs was often avoided and discouraged for safety reasons, issues with non-compliant rain heads and sump overflows were noted from ground level. Reports provided by third party inspectors also highlighted issues with poor roof tiling and gutter installations.
• On balconies, issues were most often related to waterproofing membrane failures, however design documentation lacking details for parapet wall junctions and non-compliant design of vertical upward termination heights and penetrations were also noted.
• The causes of condensation in the case studies were resultant from the presence of thermal mass (that became cold and remained that way), lack of air movement in bathroom and kitchens, thermal bridging across a wall or ceiling, and thermal bridging in single glazing.
• Site drainage issues were varied and included the ground saturation of clay soils with low permeability leading to hydrostatic pressure on slab vapour barriers, the lack of perimeter drains around a building’s external walls and the construction of planting strips in contact with external walls or within close proximity of footings.
• While none of the issues with slabs were directly associated with an identified moisture problem, bulging edges from formwork blowout or substrate containing rubbish may lead to excessive building movement which permits water ingress even before the building manifests structural concerns.
• Missing weepholes were the most frequently appearing weatherproofing non-compliance, followed by issues of direct water ingress through inadequate seals around cladding junctions, windows and doors.

The research made several recommendations including developing minimum health-related building standards, improvements to vocational and higher education of building practitioners, the development of new minimum documentation criteria around waterproofing, weatherproofing, storm-water drainage and condensation, and the adoption of digital tools and technologies to capture and document the multiple stages of weatherproofing and waterproofing to supplement mandatory inspections.

What difference this made

The research adds to the body of knowledge and evidence base to help inform policy and regulatory decisions, including future changes to the NCC and guidance for Victorian practitioners.

The research findings support the next phases of water shedding and waterproofing measures being considered by the ABCB for proposed changes to NCC 2025.

The research informed the BPC’s response and input into the Victorian position on the proposed water shedding and waterproofing measures for NCC 2025.

The research also informed the BPC’s response and input into policy and regulatory changes in Victoria for the conduct of mandatory inspections of balcony waterproofing in Class 2 residential buildings.

The research provided evidence of the relationship between poor quality design documentation, the complexities of technical requirements and non-compliant construction practices by providing an assessment of how they all contribute to water ingress defects.

To address current gaps in design documentation and improve practitioner competencies, the BPC has issued a Design Documentation Practice Guide for Class 2 residntial buildings. The Practice Guide helps improve design documentation standards by highlighting the type of information required and how compliance details and supporting information may be documented for building and structural designs, including concrete balconies and waterproofing systems. The Practice Guide addresses some of the key causal factors identified in the research.

The BPC has developed a consumer safety guide to help consumers understand the causes of water ingress on balconies, decks and terraces in their homes. The safety guide sets out simple steps that consumers can take to maintain their balconies over the life of the building and to protect their property and health by reducing water ingress damage.

A Practitioner Education webinar on Water ingress in buildings: balconies, roofs and drainage (research insights) was held on 24 October 2024 to provide practitioners with a better understanding of water ingress issues on balconies, roofs and drainage, as these are commonly reported complaints and disputes to the BPC. The webinar also covered practical tips on design documentation (drawn from the BPC’s Design Documentation Practice Guide to reduce incidences of water ingress in a building from a balcony, roof, and surfaces adjacent to the building. The webinar was presented by Dr Tim Law (RIC) and Rufaro Chakaingesu (BPC) and was attended by over 1,300 practitioners.

We are using the research insights to inform our Proactive Inspections Program and its continuing focus on areas of compliance risk that could cause water ingress and moisture damage, including through our ongoing campaign to minimise water ingress harms with a focus on balconies in Class 2 buildings. This included a planned and targeted inspection blitz on balconies that were at the right stage of construction and the issuance of directions to fix to rectify non-compliances quickly (saving consumers who end up living in these buildings time, effort and high rectification costs in the future).