What Is an FRL (Fire Resistance Level)
Date Posted:1 July 2026
What Is a Fire Resistance Level (FRL)?
A Fire Resistance Level (FRL) is a critical measure used in Australian construction to define how well a building element can withstand fire. It represents the performance of walls, floors, ceilings, doors, and other building components when exposed to fire under controlled test conditions.
FRLs are essential for ensuring buildings meet the National Construction Code (NCC) requirements and provide adequate protection to occupants and property during a fire event.
How an FRL Is Expressed
An FRL is written as a set of three numbers, separated by slashes:
Example:
120 / 120 / 120
Each number represents the number of minutes that a building element satisfies a specific performance criterion during fire exposure.
The three criteria are:
1. Structural Adequacy
This refers to the ability of a building element to maintain its load-bearing capacity during a fire.
- Prevents collapse
- Critical for structural elements like load-bearing walls, columns, and floors
- If this fails, the structure can give way, even if flames haven’t passed through
2. Integrity
Integrity measures the ability of a system to prevent flames and hot gases from passing through to the non-fire side.
- Stops fire spread between compartments
- Prevents gaps, cracks, or openings forming under fire conditions
- Essential for fire separation walls and barriers
3. Insulation
Insulation refers to the ability to limit heat transfer from the fire-exposed side to the safe side.
- Protects occupants and adjacent materials
- Prevents ignition of materials on the non-fire side
- Measured by temperature rise limits during testing
Example of FRL Ratings
- - / 60 / 60
No structural requirement (non-loadbearing), but maintains integrity and insulation for 60 minutes. - 90 / 90 / 90
Maintains full performance across all three criteria for 90 minutes. - 120 / 120 / 120
High-level fire resistance, often used in commercial and high-risk buildings.
The dash (-) means that structural adequacy is not applicable, typically for non-loadbearing elements.
How FRLs Are Determined
FRLs are established through testing under AS 1530.4, where a complete building system is exposed to fire inside a furnace.
During the test:
- Temperatures can exceed 1000°C
- The system is monitored over time
- Failure is recorded when any of the three criteria are no longer met
The time (in minutes) at which failure occurs determines the FRL.
FRL Applies to Systems — Not Just Products
One of the most important concepts to understand is that an FRL applies to a complete system, not an individual product.
For example:
- A wall system may achieve 120/120/120 only when constructed exactly as tested
- This includes specific plasterboard types, thicknesses, framing, insulation, and fixing methods
- Any variation (e.g., different sealant, larger penetration, incorrect installation) can void the FRL
This is why tested system compliance is critical in passive fire protection.
Where FRLs Are Required
FRLs are required throughout buildings to create fire compartments and slow the spread of fire.
Common applications include:
- Fire-rated walls between tenancies
- Floors separating levels
- Fire doors and shafts
- Service penetrations (pipes, cables, ducts)
- Stairwells and escape routes
The required FRL depends on:
- Building class
- Height and size
- Use and occupancy
- Fire risk level
Why FRLs Matter
FRLs are not just a regulatory requirement — they are fundamental to life safety and building performance.
A properly rated system:
- Slows fire spread
- Maintains structural stability
- Provides safe evacuation time
- Protects neighbouring spaces
Failure to meet required FRLs can lead to:
- Non-compliance with NCC
- Failed inspections
- Costly rectifications
- Increased fire risk
Key Takeaway
A Fire Resistance Level (FRL) is a time-based performance rating that measures how long a building element can resist fire in terms of structure, integrity, and insulation.
Understanding FRLs — and ensuring systems are installed exactly as tested — is essential for achieving compliant, safe, and effective passive fire protection in Australia.