Investigation of water leakage in residential apartment (concrete) balconies

What we are doing and why

The Building and Plumbing Commission (BPC) is supporting research by Swinburne University of Technology through a research grant to undertake research to identify the causes of water ingress in concrete balconies in Class 2 buildings^[1], and opportunities for improvement to current regulations, standards and work practice in balcony design and construction to reduce or eliminate water ingress.

This research is a collaboration between the BPC, Swinburne University of Technology, and Housing Industry Association. This research grant was awarded in 2022 and led by Swinburne University of Technology’s Professor Shan Shanmugananthakumar (Shan Kumar).

The research aimed to identify opportunities for improvement in the performance of concrete balcony build materials and construction methods (such as concrete mix design, falls and drains), identify different structural systems to limit balcony water ingress, and quantify the efficacies of waterproofing methods across the building lifecycle.

This research complements the research the BPC is already supporting or has conducted to minimise moisture ingress and water damage in Victorian buildings.

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 Domestic Building Dispute Resolution Victoria (DBDRV). Water proofing and drainage issues are commonly occurring areas of compliance risk the BPC identifies through the  Proactive Inspections Program and Plumbing Audit Program.

What we found

The research sourced and analysed a rich diversity of qualitative data from a systematic literature review, collection of practitioner expertise via an online survey (with 131 responses) and in-depth interviews (36 interviewees) across design engineers, architects, building surveyors, developers, waterproofing consultants and representatives from industry associations.

The research examined the practical application of balcony construction methods via case studies through eight stakeholder workshops with engineers, architects, builders and waterproofing contractors.

The research found a current heavy reliance on waterproofing membranes during the design and construction of concrete balconies of as a primary protection measure, which may underpin many of the causes of water-related defects in concrete balconies.

The research instead identifies the concrete slab as the primary protection against water ingress in concrete balconies and recommends a holistic approach which considers the inter-relationship between substrate materials, site characteristics, falls, drainage, membranes, toppings and finishing materials.

The research identified five key causes of water ingress in concrete balconies as contributing to the prevalence of water-related defects in apartment buildings:

• The installation of compliant waterproofing systems on balconies relies on clear design documentation with sufficient detailing, good coordination and planning by all relevant practitioners from the initial design stage to the delivery of the as-built constructed works. This includes the building designer, project engineers (structural and hydraulic), builders, subcontractors, product suppliers and installers. When this did not occur, waterproofing systems failed.
• The absence of a clear chain of responsibilities and accountabilities was identified across the various stages of design, construction, and maintenance of waterproofing systems for concrete balconies. This often leads to confusion on site and limited information to support the installation of compliant waterproofing systems.
• Failure of waterproofing systems were also attributed to inadequate construction processes, systems and materials coupled with lack of attention to detail, poor communication between contractors and untrained or inexperienced personnel. Further, limitations and inexperience to identify waterproofing defects during construction were also identified as a by-product of inadequate construction processes and systems.
• A lack of awareness and inattention of the required post-construction maintenance by apartment owners. During the design life of the materials forming the waterproofing system, consumers play a critical role in maintaining balconies by cleaning drainage outlets and keeping balconies free of debris and blockages.
• Further guidance, education, and training for practitioners is required to support improved technical understanding and interpretation of the National Construction Code and Australian Standards requirements when designing, detailing, constructing, and maintaining balconies.

The research makes several recommendations including improved requirements for design details, mandatory inspections of balconies at various stages, appropriate education and training, and a maintenance manual.

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. This will help better manage the risk of water ingress in future apartment concrete balconies.

We shared the research with the Australian Building Codes Board (ABCB) and other government policy makers. 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 including those occurring in concrete balconies.

To address current gaps in design documentation and improve practitioner competencies, the BPC has issued a Design Documentation Practice Guide for Class 2 residential 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 to the BPC and disputes to Domestic Building Dispute Resolution. 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.

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).

^[1]A Class 2 building is a building containing two or more sole-occupancy units where people live above, beside or below each other. This class may also include single-storey attached dwellings with a common space below, such as a carpark.