Lessons from Leaky Homes Designing Weatherproof Façades for Modern Australian Buildings

Over the last eight years, an array of reports by various research organisations has painted a stark picture of waterproofing defects in Australian buildings. In 2012, the University of New South Wales conducted a study into the issues faced by strata buildings,1 concluding that approximately 85% of multi-owned buildings built since 2000 had defects with 40% of these defects related to exterior water penetration.

In 2015, the Australian Institute of Architects found that 4% of properties inspected between 2010 and 2015 had a major water problem.2 This percentage increases to 9% in New South Wales. A further 34% of properties had a minor water problem that could turn into a costly defect if not fixed.

In 2019, Deakin University and Griffith University published the report, “An Examination of Building Defects in Residential Multi-owned Properties”.3 This report concluded that water ingress and moisture were responsible for 29% of all construction defects. Furthermore, over 33% of all cladding and building fabric defects were due to water ingress and moisture.

These three reports highlight a concerning trend – waterproofing has become the most common defect in Australia with waterproofing failures present in approximately 30% of apartment buildings. This should give property owners and industry professionals some pause as waterproofing issues often do not manifest until well into a building’s life and can be extremely difficult and costly to remediate.

In 2019, Equity Economics modelled the costs of remediating apartment defects in the last decade and estimated these to total $6.2 billion.4 Of this figure, approximately $1.4 billion is attributed to addressing water damage. This total cost does not include insurance premium increases, building audits, legal expenses and alternative accommodation. In recent years, both Canada and New Zealand faced their own leaky buildings crises with costs for remediation estimated in excess of $4 billion and $22 billion respectively.5

In this whitepaper, we discuss how the Australian waterproofing crisis has developed. In doing so, we highlight several factors designers and specifiers need to consider when designing weatherproof and compliant façade systems.

Introduction

In Australia, while there have been several reports as to the extent of waterproofing issues in buildings across the country, an investigation into the causes of the crisis has yet to be conducted. However, in Canada and New Zealand, several key factors have been identified over the years.

For Canada, blame has been directed at significant building envelope failures since the 1980s.6 A 1998 inquiry found that several factors lead to the “Leaky Condo Crisis”, including designs that were inappropriate for the climate, reliance on face-sealed wall systems, lack of build quality, and a regulatory system that was unable to understand that failures were occurring and failed to address them.7

In New Zealand, the “Leaky Homes Crisis” had several contributing factors. In 1995, the New Zealand Standard for Timber Treatment allowed for the use of untreated pine for wall framing, a timber that was susceptible to rotting when wet.8 Other factors included:

• inadequate flashings, eaves and parapets;

• poorly-designed cladding systems that allowed continuous moisture ingress into the framing;

• the use of sealants that had a propensity to fail or degrade in lieu of opting to use flashings; and

• problematic balconies that abetted significant wind transported water penetration.

While the specific factors that caused Australia’s current crisis are to be determined, both the Canadian and New Zealand experience are instructive. Although it is not specific to waterproofing, the Shergold Weir Building Confidence report9 highlighted systemic failures in Australian construction. The following key areas identified in the Shergold Weir report mirror some of the factors discussed earlier, including:

• regulatory failure;

• inappropriate design; and

• lack of quality in building products, materials and final build.

Designers, specifiers and builders need to understand how the failure areas highlighted above can help guide them in creating waterproof and compliant façades in the future.

The Waterproofing Crisis: Why It Happened

Leaking buildings are non-compliant, extremely common and very expensive. If the project or building insurance includes a non-compliant cladding exclusion, a leaky façade will not be covered. It is imperative that all involved in façade design understand the relevant building code requirements, design and testing considerations and how to address concerns with build quality.

Regulatory requirements

The National Construction Code (NCC) includes waterproofing requirements for all new Australian construction. Performance Requirement FP1.4 provides that a roof and external wall, including openings around windows and doors, must prevent the penetration of water that could cause unhealthy or dangerous conditions, or loss of amenity for occupants, and undue dampness or deterioration of building elements.

The NCC provides two pathways to compliance with FP1.4 – Performance-Based Solutions or compliance under Verification Method FV1.1. A Performance-Based Solution requires an assessment of compliance to FP1.4, which must be conducted by a suitably-qualified expert (such as a façade-engineer) and be specific to the project. Building façade tests, including those set out in AS/NZS 4284:2008 Testing of building façades, can be used as evidence of performance.

Verification Method FV1.1 is limited to buildings that are not subjected to an ultimate limit state wind pressure of more than 2.5 kPa. Compliance under this pathway comprises of the following:

• conducting a risk analysis checklist (score <20);

• testing in accordance with the requirements of AS/NZS 4284:2008; and

• testing details and conditions that match the project details.

As there is no Deemed-to-Satisfy Solution for waterproofing, every solution must be project specific. The exception to this is if a Codemark-certified solution is used, but the conditions and limitations must be reviewed with respect to the building in question. Each building will have a “serviceable” wind load pressure and an “ultimate” wind load pressure, both of which must be known in order to ascertain whether a particular solution can be used on a specific building.

Mere existence of the AS/NZS 4284:2008 test report is not sufficient for compliance. It is important to review the test report and make sure the detailing and pressures are relevant to the project, and then achieve project compliance following one of the above two pathways.

Façade Design and Compliance

Inappropriate design

Façade designs need to be appropriate for the use, climatic conditions and required performance life of the building. In both Canada and New Zealand, designs relying on sealant performance led to waterproofing issues. Over time, sealant failures resulted in leaks, which were not allowed for in the original design.

For best performance, designers and specifiers should consider the “rainscreen” system when designing façades. This approach does not prevent the use of sealant as a primary waterproofing layer, but utilises a two-layer redundant system that increases reliability. The rainscreen system is comprised of an outer leaf that sheds most of the rainwater, and an inner leaf that performs multiple functions including as a final moisture barrier, and air and vapour barrier.10 This system is combined with good drainage and drying to further protect against water ingress and mitigate the impact of site workmanship defects and sealant failures.

Another key factor for design is compliance with testing requirements. Specifically, the project should only use the various connection details that are tested to the required pressures of the project. Ensure the lining (such as sarking) is suitable for the required wind pressures. Some linings are only warranted to very low air pressures and not suitable for high rise applications.

Managing condensation and moisture build up within the wall framing is another area of concern. Façade designs must consider the climate in terms of condensation in accordance with Performance Requirement FP6.1 of the NCC. Typically, this will require the use of breathable membranes and some cavity ventilation to move the water vapour outside the building structure. The exception is in hot, humid climates where non-breathable layers are required to prevent external moisture vapour entering the air-conditioned building.

Lack of build quality

In both Canada and New Zealand, build quality issues were also identified as causing leaks and waterproofing issues. This could be a symptom of a range of issues including lack of time, profit, or skill. However, a key area of focus is the difference between testing a controlled environment and testing in real-world conditions. In the real world, conditions may not perfectly mimic the testing conditions, leading to façade systems that underperform over their service life.

To address this, it is critical to build in redundancy when designing façade systems. The two basic principles to achieve this with waterproofing are:

• over-engineer the design in relation to wind pressures; and

• use a two-layer water defense system with good drainage and ventilation.

Façades that meet these requirements are more likely to meet or exceed the relevant performance requirements in real-life conditions, even if the build does not perfectly mimic the testing sample.

Other methods for ensuring high build quality and waterproofing compliance include the following:

• If the product manufacturer conducts their own testing, request them on site during construction to ensure the install is correct. The manufacturer will be the most familiar with the system and the details required to ensure it performs as expected.

• Engage a façade engineer to peer review the cladding work being conducted. This helps ensure suitable engineering and consistency with the required installation details.

Fairview specialises in the design, manufacture and distribution of a suite of quality, aesthetically pleasing and safe cladding products to the construction industry. With almost 30 years’ experience in the facade industry, Fairview is dedicated to delivering innovative facades that meet the requirements and vision of each project.

With one of the largest stock holds in Australia, Fairview ensures a consistent and timely supply to its dedicated installer network. In addition to this, the company’s flexible and innovative approach allows their expert team to work closely with clients to deliver the best possible project outcomes.

Weatherproof and Compliant

Fairview supply cladding products that demonstrate proven performance, energy efficiency and minimal maintenance – products that are built for the future. Importantly, Fairview cladding products meet the requirements of AS/NZS 4284:2008 with test results demonstrating industry-leading performance. Test results are readily available for analysis of both serviceable and ultimate wind load pressures.

The Fairview weatherproof cladding range includes:

• Vitracore G2 – bonded aluminium panel;

• Vitradual – non-combustible cassette cladding;

• Stryüm – interlocking solid aluminium panels; and

• Equitone – pre-finished high density fibre cement.

Under independent testing in NATA-approved testing laboratories, Fairview products, namely Stryüm, Vitracore G2 and Vitradual, exceeded the minimum testing requirements and outperformed its key competitors. Waterproof testing, which measures the cladding system’s ability to prevent leakages under skyscraper-high wind pressures, proved that Fairview products performed above and beyond the 2.5kPA performance target set out in Verification Method FV1.1 of the NCC.

Fairview’s innovations and solutions teams have delivered solutions that significantly exceed building code requirements giving project stakeholders peace of mind. Fairview products are also rigorously tested to meet fire performance requirements, with exceptional durability, longevity and sustainability values.

Available in a range of profiles and customisable options, Fairview cladding combines its reliable and proven performance with limitless design flexibility to deliver modern sustainable cladding solutions ideal for Australian buildings.

Fairview

All information provided correct as of June 2020

REFERENCES

1 City Futures Research Centre. “Governing the Compact City: The Role and Effectiveness of Strata Management in Higher Density Residential Developments.” UNSW Built Environment. https://cityfutures.be.unsw.edu.au/research/projects/governing-the-compact-city-the-role-and-effectiveness-of-strata-management-in-higher-density-resi-dential-developments (accessed 23 June 2020).

2 Castle, Jemmy. “Apartment building defects.” CHOICE. https://www.choice.com.au/money/property/buying/articles/apartment-building-defects (accessed 23 June 2020).3 Johnston, Nicole and Sacha Reid. “An Examination of Building Defects in Residential Multi-Owned Properties.” Griffith University.

https://www.griffith.edu.au/__data/assets/pdf_file/0030/831279/Examining-Building-Defects-Research-Report.pdf (accessed 23 June 2020).4 Equity Economics and Development Partners Pty Ltd. “The Cost of Apartment Building Defects.” Equity Economics.

http://www.equityeconomics.com.au/the-cost-of-building (accessed 23 June 2020).5 Laxon, Andrew. “It’s not if - it’s when for our dripping time bombs.” New Zealand Herald.

https://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10628820 (accessed 23 June 2020).6 Commission of Inquiry into the Quality of Condominium Construction in British Columbia. “Chapter Two: The Framework of Residential Construction.” Queen’s Printer.

http://www.qp.gov.bc.ca/condo/c2_ii.htm (accessed 23 June 2020).7 Ibid. 8 New Zealand Government. “Dealing with Timber in Leaky Buildings.” Department of Building and Housing.

https://www.building.govt.nz/assets/Uploads/building-code-compliance/e-moisture/e2-external-moisture/guide-timber-in-leaky-buildings.pdf (accessed 23 June 2020).9 Shergold, Peter and Bronwyn Weir. ”Building Confidence.” Department of Industry, Science, Energy and Resources.

https://www.industry.gov.au/sites/default/files/July%202018/document/pdf/building_ministers_forum_expert_assessment_-_building_confidence.pdf (accessed 23 June 2020).

10 Metal Construction Association. “Understanding Rain Screen Wall Systems.” MCA. https://www.saf.com/wp-content/uploads/2011/09/mca07_Rainscreen.pdf (accessed 23 June 2020).