Fire Compartmentation Requirements for Class 2 Buildings

What This Requirement Covers

Fire compartmentation for Class 2 buildings (apartments and other sole-occupancy units in the same building) sets the minimum construction measures to limit the spread of fire and smoke within a building, protect means of egress, and reduce risk to occupants and firefighters. Compartmentation divides a building into fire compartments and fire-isolated exits using fire-resisting walls, floors, doors and protected shafts so that fire size and smoke movement are controlled while occupants evacuate or are assisted. The requirement exists to meet the NCC Objectives and Performance Requirements for structural stability, prevention of fire spread, safe evacuation, and protection of openings and services (see C1O1, C1P2, C1P4).

These provisions apply to designers, builders, certifiers and owners of Class 2 buildings under the National Construction Code (NCC) - Volume One. They also inform product selection, detailing of penetrations and junctions, and the application of state schedules and alternative solutions where the Deemed-to-Satisfy (DtS) provisions are not used.

Key Requirements

1. Fire compartments and maximum compartment size: The DtS provisions in Part C3 limit the size and volume of fire compartments for certain building classes - relevant DtS tests and tables are found in C3D3 and related clauses in NCC Volume One. Consult C3D3 for the specific maximum area/volume limits that apply to multi-class buildings. (See NCC Volume One, Part C3, C3D3.)
2. Fire-resisting construction (FRL) for separating elements: Elements separating fire compartments, and elements bounding exits and sole-occupancy units, must achieve the required FRL (e.g., 60/60/60, 120/120/120) where specified by Tables and Deemed-to-Satisfy provisions. Exact FRLs depend on location, construction type and rise in storeys - see C2D2, C2D3, and Specification 5. (See NCC Volume One, Part C2 and Specification 5.)
3. Separation of Class 2 parts and public corridors: Construction bounding Class 2 sole-occupancy units and public corridors must meet the construction and lining requirements in C4D12 and C3D15. Internal walls bounding sole-occupancy units commonly require plasterboard lining to achieve the necessary fire performance (e.g., 13 mm standard plasterboard or equivalent) in accordance with C4D12. (See NCC Volume One, C4D12 and C3D15.)
4. Fire-isolated exits and protected shafts: Stairways, lift shafts and other fire-isolated exits must meet the Deemed-to-Satisfy provisions for enclosure, minimum FRLs and protection of openings (see C3D11, C3D12 and C4D11). Fire-isolated exits are required where they form part of an evacuation strategy supporting C1P4. (See NCC Volume One, C3D11-C3D12 and C4D11.)
5. Protection of openings and penetrations: Openings in fire-resisting construction must be protected with fire doors, shutters or glazing with the appropriate fire-resistance level and smoke control as specified in Part C4 (for example, door sets in fire walls must meet the FRL and smoke limitations in C4D6 and C4D5). Service penetrations must be sealed to retain the FRL of the element (see C4D15, C4D13, C4D16). (See NCC Volume One, Part C4.)
6. Public corridor requirements in Class 2: Public corridors in Class 2 buildings are covered by C3D15, which sets separation and construction requirements to ensure corridors are protected routes for evacuation. (See NCC Volume One, C3D15.)
7. Construction type and rise in storeys affect compartmentation: The required type of construction (Type A, B or C) and calculation of rise in storeys modify FRLs and compartment sizes under C2D2 and C2D3. These in turn affect required compartmentation measures. (See NCC Volume One, C2D2, C2D3.)
8. Materials and lining: Where plasterboard lining is prescribed (for internal walls between sole-occupancy units or bounding corridors), 13 mm standard grade plasterboard (or material with equivalent fire protection) is commonly specified in the DtS clauses such as C3D6 (state variations also affect this). Penetration and junction treatments must comply with Specification 5 and relevant Australian Standards for seals and fire-stopping. (See NCC Volume One, C3D6 and Specification 5; in accordance with AS 1530 series and AS 1905 for fire-resistant glazing and seals.)
9. Standards referenced: Use materials and systems in accordance with relevant Australian Standards where cited by the NCC, for example AS 1530 series for fire tests, AS 1905 series for fire-resistant glazing and assemblies, and other product standards as referenced by Specification 5. Product systems should be installed in accordance with the manufacturer’s tested system and relevant standards such as AS 1684 where timber framing interfaces are involved, and AS 3700 for masonry where applicable.

Relevant references: NCC Volume One - Part C1, Part C2, Part C3 (including C3D3, C3D11, C3D12, C3D15), Part C4 (C4D11, C4D12, C4D13, C4D15), Specification 5 - Fire-resisting construction.

Residential vs Commercial

1. Class 2 (residential apartment) requirements are set within NCC Volume One and address compartmentation between sole-occupancy units, public corridors and vertical shafts. The focus is on protecting shared circulation spaces and providing fire-isolated exits for multi-occupancy residential buildings (see C3D15 and C4D12).
2. By contrast, Class 1 and Class 10 buildings (detached houses, carports and ancillary structures) fall under NCC Volume Two and the ABCB Housing Provisions. Separation of dwellings and fire protection of separating walls/floors in Class 1 are dealt with in Volume Two - Part H (for example, H3D4 and Part 9.3 of the ABCB Housing Provisions) and typically permit different, generally less onerous DtS measures (see NCC Volume Two, H3D4 and ABCB Housing Provisions Part 9.3).
3. Commercial buildings (Class 3-9) use the same Volume One compartmentation framework as Class 2, but compartment sizes, required FRLs and additional protection (sprinklers, smoke control) often differ because of higher occupant loads, different uses and greater fire load. Tables and clauses in Part C3 specific to building types should be applied to each classification.

Exceptions and Exemptions

1. Performance Solutions: Where the DtS provisions are not appropriate, a Performance Solution may be adopted provided the solution meets the Performance Requirements in Part C1 (see C1P1-C1P9) and follows the Verification Methods. A documented fire engineering solution can vary compartment sizes, FRLs or protective measures.
2. Sprinkler concessions: Installation of an automatic sprinkler system may modify some DtS limits (e.g., compartment sizes and certain FRL requirements) where the NCC or relevant specification permits concessions - check specific clauses and the relevant Specification for sprinkler concessions (see applicable parts of Part C and Specification references).
3. Small buildings and certain building elements: Some small isolated areas or specific ancillary elements may be exempted or permitted lower performance (see C3D2 Application of Part and C2D14 Ancillary elements). Specific exemptions depend on size, use and presence of sprinklers or other systems.
4. State schedules may impose additional exceptions or stricter controls - always review the state schedule for your jurisdiction in NCC Volume One (Schedules 4-12).

State and Territory Variations

1. Each state and territory may amend or add requirements in its schedule to NCC Volume One. For example, New South Wales includes modifications for construction and lining requirements and specific wording in its schedule (see NSW modifications to C3D6 in NCC Volume One Schedule for NSW). Always check the State Schedule in NCC Volume One (Schedules 4-12) for jurisdictional amendments.
2. Common areas of variation include required lining of walls between sole-occupancy units, minimum FRLs for certain separating elements, and additional requirements for smoke control or sprinkler provision. Queensland, Victoria and NSW commonly publish guidance and specific schedule changes - verify the applicable Schedule for your project location in NCC Volume One.

Practical Compliance Tips

1. Coordinate early with the certifier or fire engineer: Confirm whether you will use DtS provisions or a Performance Solution before preparing detailed drawings so compartment sizes and FRLs are set early.
2. Apply the correct building classification and rise-in-storeys: The required FRLs and compartmentation measures depend on classification and rise in storeys - get the classification and rise calculation right using C2D2 and C2D3 to avoid rework.
3. Specify tested systems for penetrations and junctions: Use fire-stopping and sealing systems with test evidence that matches the required FRL and the product manufacturer’s installation instructions - record test evidence and installation details on drawings (see C4D15 and Specification 5).
4. Protect corridor enclosures and doors: Ensure corridor walls, doors and door frames meet the specified FRL and smoke-control requirements in C3D15 and C4D6 - common failures are underspecified door sets and inadequate seals around doors.
5. Don’t assume plasterboard thickness without checking: Where the DtS clauses require plasterboard lining (for example 13 mm standard grade on certain internal walls), confirm the type, number of layers and fixing manufacturers’ details to meet the prescribed FRL and NCC clause (see C4D12 and C3D6/National and State variations).
6. Consider sprinklers as a design lever early: A sprinkler system can allow concessions to compartment sizes and additional flexibility but affects services design - include sprinkler scope early to coordinate services penetrations and hydrant/riser locations.
7. Check state schedules and local council requirements: State schedules can change lining and FRL requirements; check the applicable NCC Volume One state schedule and local council practice prior to finalising details.

References (examples of required citation locations in the NCC): NCC Volume One - Part C1 (Objectives and Performance Requirements), Part C2 (Type of construction and FRLs), Part C3 (Compartmentation - C3D3, C3D11, C3D12, C3D15), Part C4 (Protection of openings - C4D11, C4D12, C4D13, C4D15), Specification 5 - Fire-resisting construction. Also refer to relevant Australian Standards such as AS 1530 series, AS 1905 series, AS 1684 and AS 3700 where cited by the NCC.

Could not determine from the documentation whether any project-specific product approvals or local council policies apply - always confirm with the certifier and refer to the relevant state schedule in NCC Volume One for jurisdictional amendments.