The Hidden Risks in Exterior Wall Assemblies

In modern construction, we’ve made buildings lighter, more energy efficient, and more visually striking than ever before using exterior cladding or façade systems.

These systems include combustible materials like aluminium composite panels, foam insulation, timber, and decorative laminates. While these materials offer benefits such as improved thermal performance and design flexibility, they can also introduce serious risks as they can significantly influence how a fire behaves.

Over the past two decades, several major fires around the world have demonstrated how quickly fire can spread on the outside of buildings when combustible materials are involved. Events such as the Grenfell Tower and Lacrosse Apartment fire highlighted how façade systems can contribute to rapid fire growth, trapping occupants, overwhelming firefighting efforts and bypassing many of the protections we rely on inside buildings.

Why Exterior Wall Systems Can Be Dangerous in a Fire

Most people think of fire spreading internally—from room to room. But façade systems introduce a different pathway: external vertical fire spread. As the Building Code of Australia (BCA) focuses on fires developing inside a building, external fire sources are not really considered, with the exception of limits around building too close to a fire source feature.

Exterior wall systems are not just a single material—they are complex assemblies. These can include external panels (e.g. aluminium composite panels), insulation, air cavities, sarking, membranes and fixings. When combustible materials are used, and particularly if cavity barriers are missing or compromised, these systems can act as a hidden fuel package.

Even though research shows that façade fires represent a relatively small percentage of total building fires, they can result in disproportionately high damage and life risk.

Common Combustible Materials in Facades

Several materials commonly used in construction can contribute to fire spread:

• Aluminium Composite Panels (ACP): These panels often contain a polyethylene (plastic) core, which is highly combustible and can burn intensely once ignited.
• External Insulation Systems: Foam insulation such as expanded polystyrene (EPS) can melt, ignite, and spread fire rapidly if not properly protected.
• Timber and Laminates: While increasingly popular for sustainability reasons, these materials must be carefully designed and detailed to limit fire risk. This includes high-pressure laminate (HPL) cladding.

Following multiple incidents, these materials became the focus of audits and regulatory reforms across several states. In particular, Victoria and New South Wales undertook large-scale cladding rectification programs affecting hundreds of buildings.

Where Things Go Wrong in Practice

Fires involving façades can begin in many ways, for instance, when a fire inside a building breaks through a window, or when an electrical fault sparks on the balcony or from hot works during renovations.

The fire can then spread to the levels above via openings like windows, to the levels below from falling burning debris, up the external surface of the wall, through the vertical cavity and to combustible elements internal to the wall system when the heat causes degradation and separation of non-combustible protective skin.

From audits, expert reports, and fire investigations, the same issues consistently arise:

• Missing or incorrectly installed cavity barriers.
• Poor detailing around windows, slab edges, and penetrations.
• Substitution of compliant materials with non-compliant products.
• Lack of clarity around Performance Solutions vs Deemed-to-Satisfy compliance.
• Gaps between design intent and as-built construction.

There are also different ways of interpreting BCA requirements and this is why so many buildings were able to be built with combustible facades. In many cases, buildings technically complied with the BCA at the time of construction.

A Global Wake-Up Call

The Grenfell Tower fire changed the global conversation on building safety. The 2017 fire brought worldwide attention to the dangers of combustible façade systems. A fire that started inside a single apartment rapidly spread up the exterior of the building, with catastrophic consequences.

But this wasn’t an isolated case. Others include:

• Shanghai Apartment Fire, China (2010) – PU (polyurethane) insulation
• Tamweel Tower, UAE (2012) – ACP (PE core)
• Mermoz Tower, Roubaix France, 2012 – ACP (PE core)
• Al Tayer Tower, Sharjah, 2012 – ACP (PE core)
• Saif Belhasa Building, Tecom, Dubai 2012 – ACP (PE core)
• Al Hafeet Tower, UAE (2013) – ACP (PE core)
• Lacrosse Building, Australia (2014) – ACP (PE core)
• The Marina Torch, UAE (2015) – ACP (PE core)
• Baku Residential Tower, Azerbaijan (2015) – ACP (PE core)
• Al Nasser Tower, UAE (2015) – ACP (PE core)
• Address Downtown, UAE (2015) – ACP (PE core + decorative façade panels)
• Sulafa Tower, UAE (2016) – ACP (PE core)
• Shepherd’s Court, UK (2016) – EIFS (EPS insulation system)
• Grenfell Tower, UK (2017) – ACM (PE core) + PIR insulation + cavity façade system
• Neo200, Australia (2019) – ACP (PE core elements)
• Abbco Tower, UAE (2020) – ACP (PE core)
• Ulsan Samhwan Tower, South Korea (2020) – ACP + insulation system
• The Cube (Bolton), UK (2019) – HPL
• Torre del Moro, Italy (2021) – HPL + combustible insulation
• Valencia Residential Towers, Spain (2024) – HPL + combustible insulation

Most of these incidents demonstrate the same general pattern – the fire originated internally or on a balcony; ignition of the external wall system; vertical fire spread, bypassing internal fire suppressions systems. This is fundamentally different from how we traditionally expect buildings to behave in a fire.

Do Current Fire Tests Reflect Real Risks?

There are many different international test methods used to assess façade fire performance and to  attempt to simulate fire spreading on a building façade. However, research has identified some limitations. Test setups vary significantly between standards and real-world features like windows, joints, and construction defects are not always fully represented. Consequently, results can differ depending on how the system is configured.

How to Improve Fire Safety in Exterior Walls

High-rise building external wall fire safety can be improved by using non-combustible materials or flame-retardant materials and correctly installing cavity barriers and fire breaks. Closing the design to construction gap ensures what is built matches the approved fire engineering design and documentation. This relates to building product traceability and product substitution.

There is a growing push for more realistic, large-scale testing that better reflects actual building conditions – not just products in isolation, but entire wall assemblies.

Sprinklers can prevent internal fires from spreading to external facades but are less effective for direct exterior fires. There is also no external fire detection (although there are some attempts to develop detection embedded into facades).

Building codes are increasingly restricting combustible materials in certain building types, but consistent enforcement is critical with clearer accountability. When designing and approving, it is important to focus on the intent of the BCA rather than the exact wording.

Safety is ultimately improved by ongoing education – From architects, builders, developers, procurers and certifiers, understanding façade fire risk is still developing across the industry.

Final Thoughts

Façade fires are not the most common type of building fires, but when they occur, the consequences can be devastating. What makes these fires particularly dangerous is their ability to spread rapidly outside the normal fire protection systems within a building.

Fire safety is not just about materials. It depends on design, installation, regulation and maintenance working together. As buildings continue to evolve, ensuring that fire safety keeps pace remains a critical challenge for the industry.

As buildings become more complex, the challenge for our industry is clear – compliance does not always equal safety. We must ensure that performance, practicality, and fire safety evolve together—not in isolation.

To learn more about combustible cladding from a engineering & expert witness viewpoint, enrol in: https://cjkfireandsafety.com.au/courses/combustible-cladding/

To learn more about combustible cladding from a engineering & expert witness viewpoint, enrol in this short course: https://cjkfireandsafety.com.au/courses/combustible-cladding/

Sources

• White, Nathan and Delichatsios, Michael (2014). Fire Hazards of Exterior Wall Assemblies Containing Combustible Components (Additional sources as cited in the full paper)
• https://www.nfpa.org/codes-and-standards/nfpa-285-standard-development/285
• https://knowledge.bsigroup.com/products/fire-performance-of-external-cladding-systems-test-method-for-non-loadbearing-external-cladding-systems-fixed-to-and-supported-by-a-masonry-substrate
• https://www.iso.org/standard/27183.html
• https://www.intertek.com/building/standards/can-ulc-s134/
• https://ncc.abcb.gov.au/news/2020/demonstrating-ncc-compliance-using-5113
• National Fire Incident Reporting System (NFIRS) data
• National Institute of Standards and Technology façade fire studies