When people think about fire safety in buildings, they typically picture sprinklers, alarms and extinguishers. But the first line of defence in any building fire is passive: the walls, floors, doors and seals that contain fire and smoke within a defined zone, buying time for evacuation and limiting the spread of damage.
What is Passive Fire Compartmentation?
Compartmentation is the division of a building into discrete fire compartments using fire-resisting construction elements. The purpose is to limit the spread of fire and smoke — giving occupants time to evacuate safely, limiting damage to a defined zone, and enabling firefighters to manage the incident.
BCA Section C — Fire Resistance and Stability
The BCA's requirements for compartmentation are found in Section C (NCC 2022: Part C), covering fire resistance and structural stability. Key provisions include requirements for fire resistance of load-bearing and non-load-bearing elements, separation between occupancy classes, fire compartment sizes and protection of openings.
NCC 2022 Update
The NCC 2022 restructured the fire provisions significantly. Section and clause numbering differs from BCA 2019 and earlier. Always confirm which edition of the NCC applies to your project.
Fire Resistance Levels (FRL) Explained
An FRL is expressed as three numbers separated by slashes representing time in minutes for Structural Adequacy / Integrity / Insulation. An FRL of 120/120/120 means all three criteria achieved for 120 minutes. A dash means that criterion is not required — for example –/120/120 for a non-load-bearing partition wall.
Key Compartmentation Elements
Fire Walls
Fire walls are the primary means of dividing a building into fire compartments. They typically extend from the floor slab to the underside of the floor above, and their FRL must match the required compartment separation for the building class and storey.
Fire Doors
Every opening in a fire wall requires a fire door or compliant protecting element. Fire doors must achieve an FRL consistent with the wall they protect, be fitted with self-closing devices, have compliant hardware throughout, and be maintained under AS 1851 Section 17.
Service Shafts
Lift shafts, stair shafts and service risers must be enclosed in fire-resisting construction to prevent them acting as chimneys for smoke and fire spread between floors.
Penetrations and Service Openings
Every pipe, cable, duct or conduit passing through a fire-rated wall or floor creates a potential weakness. The BCA requires that penetrations be protected by fire-stopping systems achieving an FRL not less than the element itself, per AS 4072.1.
Cumulative Penetration Problem
Each time a tradesperson runs a new cable through a fire-rated element without a compliant seal, a new breach is created. In buildings more than a decade old, it is common to find fire-rated walls with dozens of unsealed penetrations.
Documentation Requirements
For new construction, fire resistance must be demonstrated through the construction certificate and occupation certificate process. For existing buildings, the AFSS requires that passive fire protection elements are assessed and certified annually by an accredited AFSP — requiring as-built records, fire door service records, and penetration seal documentation.
Put This Into Practice
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