Fire Resistance Levels and External Walls: What Facade Specifiers Need to Know
Fire Resistance Level - FRL - is one of the most frequently referenced terms in NCC compliance, and one of the most frequently misunderstood when it comes to facades. Specifiers regularly ask whether cladding needs to be “fire-rated.” The short answer is that fire resistance applies to the wall assembly, not to the cladding material on its own. But the longer answer matters, because getting this wrong can stall approvals, create unnecessary cost, or leave genuine compliance gaps unaddressed.
This article sets out how FRL works for external walls, when it applies, how it interacts with facade cladding, and where the common confusion sits between fire resistance and non-combustibility.
What is a Fire Resistance Level?
An FRL is expressed as three numbers separated by slashes - for example, 120/120/120 or 90/60/60. Each number represents a duration in minutes for a specific performance criterion, tested to AS1530.4:
- Structural adequacy - the time a loaded element can carry its design load under fire conditions
- Integrity - the time an element prevents the passage of flames and hot gases through it
- Insulation - the time an element limits the temperature rise on the unexposed face
When a wall is required to achieve an FRL of 90/90/90, it means the entire wall assembly must maintain structural stability, prevent fire and gases from passing through, and limit heat transfer on the non-fire side for at least 90 minutes.
The critical point: FRL is a property of the complete wall assembly, not of any single material within it. A concrete wall, a fire-rated steel-framed plasterboard wall, and a masonry wall can all achieve an FRL. The cladding fixed to the exterior of that wall is not the element being rated.
When do external walls need an FRL?
Not all external walls require an FRL. The requirement depends on how close the wall is to fire-source features - boundaries, the centreline of an adjoining allotment, or other buildings on the same site.
NCC Volume One, Specification C1.1, Table 3 sets out these requirements. The closer an external wall sits to a fire-source feature, the more likely it needs an FRL. The general logic is straightforward:
- Walls very close to boundaries (typically less than 1.5m) usually require an FRL from both sides - meaning the wall must resist fire whether the fire originates internally or externally.
- Walls at moderate distances (1.5m to 3m, depending on building classification and construction type) may require an FRL from the outside only - protecting against radiant heat from an adjacent fire.
- Walls further from boundaries may not need an FRL at all.
The building classification and type of construction (Type A or Type B) also influence the specific FRL values required. A Class 2 residential building close to a boundary may need a different FRL than a Class 5 office building at the same distance. The fire engineer determines these requirements for each project based on the NCC provisions and the specific site conditions.
FRL vs non-combustibility: two different requirements
This is where the most common confusion sits. Specifiers sometimes conflate fire resistance and non-combustibility, or assume one implies the other. They are separate requirements under the NCC, tested to different standards, measuring different things.
Non-combustibility is a material property. Tested to AS1530.1, it determines whether a material will burn, sustain flame, or contribute significant heat when exposed to 750 degrees Celsius. The NCC requires external cladding materials in Type A and Type B construction to be non-combustible. This is about what the cladding is made of.
Fire resistance is an assembly performance measure. Tested to AS1530.4, it determines how long a complete wall system can resist the effects of fire - structural collapse, flame penetration, and heat transfer. This is about how the wall performs as a system.
These requirements operate independently:
- A facade can be non-combustible without having an FRL. An interloQ rainscreen system on an external wall that is set well back from the boundary may not need any fire resistance, but the cladding still needs to be non-combustible.
- A wall that needs an FRL achieves it through the structural wall behind the cladding - the concrete, blockwork, or fire-rated steel frame and plasterboard - not through the cladding itself.
- A wall could theoretically have an FRL without having non-combustible cladding, though the NCC would typically require both where they apply.
When someone asks for “fire-rated cladding,” what they usually need is non-combustible cladding fixed to a fire-rated wall. The cladding satisfies the non-combustibility requirement. The wall behind it satisfies the FRL requirement. Different tests, different elements, different documentation.
How facade cladding interacts with fire-rated walls
The facade cladding is the outermost layer of the external wall, but it is not the fire-rated element. The fire rating comes from the wall construction behind it.
For rainscreen systems like interloQ or solid panel systems like element13, the cladding sits outboard of the fire-rated wall on a subframe. The wall assembly - whether it is 200mm concrete, reinforced blockwork, or a fire-rated steel stud and plasterboard system - is what achieves the FRL. The cladding provides weather protection, aesthetics, and non-combustibility, but the fire resistance performance belongs to the structure behind it.
This means the cladding selection does not change the FRL of the wall. Whether the exterior finish is aluminium rainscreen, rendered blockwork, or precast concrete, the fire resistance of the wall assembly depends on its internal composition and construction. The cladding must be non-combustible where the NCC requires it, but that is a separate compliance pathway.
Curtain wall: a different situation
The 165CW unitised curtain wall system presents a different arrangement. In a curtain wall facade, the curtain wall is the external wall - there is no separate structural wall behind it at the facade line. The curtain wall spans between floor slabs and carries its own weight plus wind loads.
Fire resistance at floor levels in curtain wall construction is typically addressed through the spandrel zone - the opaque area between the top of one window and the bottom of the next, aligned with the floor slab. Fire resistance in this zone is achieved through fire-rated spandrel panels, back-pans with fire-resistant insulation, and perimeter fire barriers (also called slab-edge protection or linear gap seals) at the junction between the curtain wall and the concrete floor slab.
The curtain wall framing itself is not the fire-rated element. The fire performance is delivered by the rated components integrated behind and around the visible framing - the insulated back-pan, the perimeter fire barrier, and the floor slab. The fire engineer specifies these requirements, and the curtain wall design must accommodate them within the system.
What Valmond & Gibson provides - and where responsibilities sit
As a facade system supplier, Valmond & Gibson provides non-combustibility evidence for our aluminium products. interloQ, element13, and 165CW are all tested to AS1530.1 and classified as non-combustible by CSIRO. That documentation is available and forms part of the compliance evidence package for any project.
FRL requirements are determined by the fire engineer based on the building classification, construction type, distance to fire-source features, and any performance solutions adopted. The wall assembly that achieves the required FRL is designed by the structural and fire engineers, not by the facade supplier.
Our role is to ensure the cladding meets its non-combustibility requirements and to provide clear, well-organised documentation that makes the certifier’s job straightforward. The fire resistance of the wall behind the cladding sits with the engineering team.
Practical guidance for specifiers
A few points that can save time in the specification and approval process:
Separate the two requirements early. When preparing facade specifications, address non-combustibility and FRL as distinct line items. The cladding material satisfies one. The wall assembly satisfies the other. Keeping them separate in the specification avoids confusion during certification.
Check Table 3 of Specification C1.1 early in design. Understanding whether external walls need an FRL - and from which side - influences wall construction, not cladding selection. If a wall needs an FRL from both sides, the structural design must accommodate that regardless of what cladding goes on the outside.
Do not ask for “fire-rated cladding” unless you mean it. In most cases, what is needed is non-combustible cladding on a fire-rated wall. Using precise language avoids unnecessary product evaluations and speeds up the approval process.
Coordinate between fire engineer and facade consultant. FRL requirements, non-combustibility requirements, and spandrel zone detailing in curtain wall systems all need to align. Early coordination prevents clashes between the structural fire rating and the facade design.
Request compliance documentation early. Non-combustibility test reports (AS1530.1), fire resistance test reports for wall assemblies (AS1530.4), and perimeter fire barrier details should all be assembled before the certifier reviews the facade. Waiting until the project is on site to compile this documentation is a common and avoidable cause of delays.
Summary
FRL applies to wall assemblies, not cladding materials. Non-combustibility applies to cladding materials, not wall assemblies. They are separate requirements under the NCC, tested to different standards, and satisfied by different parts of the external wall construction. Understanding where each requirement sits - and who is responsible for demonstrating compliance - is fundamental to a smooth approval process and a compliant building.
For non-combustibility evidence on interloQ, element13, or 165CW, contact the Valmond & Gibson team directly. For FRL requirements, engage your fire engineer early.
Related Reading
- AS1530.1 and AS1530.3: What Facade Fire Tests Actually Measure
- NCC Facade Requirements by Building Class
- NCC Compliance for Mixed-Use Buildings
- 165CW Curtain Wall Specification Guide
Last updated: 4 April 2026