Combustible Cladding Restrictions and Testing Requirements

What This Requirement Covers

The combustible cladding restrictions and testing requirements in the National Construction Code (NCC) govern the use, performance verification and installation of externally applied cladding materials that are combustible or include combustible components. These rules exist to reduce the risk of rapid external fire spread via building façades, protect occupant egress and limit property and adjacent-building exposure to external fire. The requirements are aimed at manufacturers, designers, certifiers, builders and building owners responsible for selecting, specifying, installing and verifying cladding systems.

The requirements apply where an external wall or cladding system could contribute to external fire spread, including rainscreen systems, bonded laminated panels, aluminium composite panels, timber cladding, polymeric facings, insulated panels and assemblies with combustible cores. The NCC sets out both Deemed-to-Satisfy provisions and verification/test methods (and state schedules may impose stricter limits or prohibitions) so that compliance can be demonstrated by prescribed tests or by meeting specific non-combustible construction rules.

Key Requirements

1. Scope and objective: Requirements are primarily in NCC Volume One (Parts C1 and C2, including C1V3, C2D11, C2D12, C2D15) and in state schedules that modify Performance Solutions or Deemed-to-Satisfy paths. See NCC Volume One - Section C (Fire resistance) and Deemed-to-Satisfy Provisions C2D11 to C2D15 for external wall and cladding provisions.
2. Testing standards required:
3. Assemblies intended to demonstrate fire hazard properties must be tested to AS/NZS 1530.3 for Spread-of-Flame Index and Smoke-Developed Index, and to AS 1530.4 (Standard Fire Test) for ability to prevent ignition and to screen core materials from free air, as specified in Specification 3 (S3C3) of the NCC Volume One/Two schedules.
4. For external combustible cladding systems (where relevant), the NCC and state schedules require form-of-test and specimen representation in accordance with S3C4 and S3C6 (test specimens must incorporate joints, perforations and representative fixings; pilot-scale permitted ≥ 900 mm x 900 mm or other specified sizes when justified).
5. Interface temperature and timber protection tests:
6. Where timber interface protection is claimed, tests must measure interface temperature and record time above 300°C using thermocouples positioned at joints, 200 mm from joints, at penetrations and other critical points (see Table S10C3, S10C4 in NCC Volume One - Specification 10 and related requirements). Smaller pilot specimens may be permitted provided minimum size 1000 mm x 1000 mm for some timber protection tests and prior full-scale validation as required by S10C5.
7. Bonded laminated cladding fixing:
8. In buildings required to be of Type A or B construction, externally located bonded laminated cladding panels must have all layers mechanically supported or restrained to the supporting frame (C2D15(1)). Mechanical fixing excludes reliance solely on chemical adhesives and includes cassette fixing, channel-type fixing and face fixing. Exceptions for specific materials (laminated glass systems, layered plasterboard product, fibrous-plaster sheet, fibre-reinforced cement sheeting, garage door components) are listed in C2D15(2).
9. Cavity and test specimen provisions:
10. For cavity walls and unique wall systems the NCC sets specific specimen features to be included in tests - e.g., representative cavity details, header/footer systems and openings such as a 15 mm diameter hole in the internal lining below a window for some test setups (see relevant Verification Methods H2P3 and S3C4).
11. Deemed-to-Satisfy vs Performance Solution limits:
12. Some combustible cladding may be acceptable for low-rise applications under specific Deemed-to-Satisfy provisions (e.g., C2D6 for two-storey Class 2, 3 or 9c). However, Performance Solutions for combustible cladding in certain multi-storey or higher-risk buildings are restricted by state schedules (see State and Territory Variations below).
13. Referenced Australian Standards:
14. AS/NZS 1530.3 - Methods for fire tests on building materials, components and structures - Measurement of fire-propagation, heat release and smoke release.
15. AS 1530.4 - Standard Fire Tests of Building Construction and Materials (used to assess ignition and screening of core material).
16. (Other standards commonly referenced for cladding design and fixing: AS 1684 for timber framing connections, AS 4100 for steel structures, AS 3700 for masonry; these are relevant to structural fixing and design but not the fire test methods themselves.)

Residential vs Commercial

1. Residential (Class 1 and 10):
2. Detached houses and some single-storey residential outbuildings typically have more permissive Deemed-to-Satisfy pathways for combustible cladding, provided the wall construction meets relevant fire hazard requirements and the building does not present a higher risk of external fire spread. For example, small Class 1 buildings are not usually captured by the same restrictions that apply to multi-storey Class 2-9 buildings. However, where a Class 1 building adjoins a more vulnerable building or has atypical design features (e.g., large vertical expanses of combustible cladding), testing to AS/NZS 1530.3 or AS 1530.4 may still be required to demonstrate safety.
3. Commercial and multi-residential (Class 2 to 9):
4. These classes are more tightly regulated for combustible cladding, particularly where rise in storeys exceeds thresholds in C2D6 or where state schedules explicitly restrict Performance Solutions. For example, many jurisdictions disallow Performance Solutions to justify combustible cladding on Class 2, 3, 5-9 buildings with a rise in storeys of 2 or more (jurisdictional variations apply). Bonded laminated cladding panels on Type A or B construction must be mechanically restrained (C2D15).

Exceptions and Exemptions

1. Specific materials exempted from mechanical-support rules for bonded laminated panels are listed in C2D15(2): laminated glass systems, layered plasterboard, perforated gypsum lath with normal paper finish, fibrous-plaster sheet, fibre-reinforced cement sheeting and components of garage doors.
2. Pilot-scale testing concessions: Accredited Testing Laboratories may accept reduced specimen sizes where justified - commonly 900 mm x 900 mm for AS 1530.4 pilot tests of assemblies (S3C6) and 1000 mm x 1000 mm for some timber interface tests (S10C5), provided prior validation by full-scale tests and limits stated by the testing laboratory are respected.
3. State schedules may prohibit Performance Solutions for combustible cladding in higher-risk situations regardless of test results. Where a state schedule expressly restricts Performance Solutions, a tested Performance Solution may still be disallowed by the jurisdiction (see State and Territory Variations).

State and Territory Variations

1. The NCC is adopted nationally but each state and territory has its own schedule in NCC Volume One that can modify or prohibit Performance Solutions for combustible cladding. For example:
2. Victoria: Schedule inserts (VIC A2G2(5)) expressly prevent a Performance Solution being used to justify combustible cladding products on external walls of certain buildings - for example, Class 2, 3 or 9 buildings with a rise in storeys of 2 that do not comply with C2D6; and Class 2, 3, 5, 6, 7, 8 or 9 buildings with a rise in storeys of 3 or more (NCC Volume One and Volume Two state inserts). See NCC 2022 Volume One - Part A2 and related state schedule text.
3. Other states and territories have similar or differing thresholds in their schedules. Always check the relevant state schedule (Schedules 4-12 in NCC Volume One) for local variations and prohibitions that may override national test-based compliance.

Practical Compliance Tips

1. Early material selection: Choose cladding systems with documented test evidence to NCC-prescribed standards (AS/NZS 1530.3 and AS 1530.4) before detailed design to avoid costly redesign if the jurisdiction disallows Performance Solutions.
2. Check state schedules first: Before commissioning tests or pursuing a Performance Solution, confirm the applicable state schedule in NCC Volume One as some jurisdictions prohibit Performance Solutions for combustible cladding above specific storey thresholds (e.g., Victoria’s VIC A2G2(5)).
3. Use Accredited Testing Laboratories: Ensure tests are done by an Accredited Testing Laboratory and that specimens include representative joints, fixings and penetrations per S3C4 and S3C6; accept pilot-scale only where expressly permitted and documented.
4. Document mechanical fixing: For bonded laminated panels on Type A or B construction provide clear design and documentation showing mechanical support or restraint (not solely adhesive) in accordance with C2D15; include fixing schedules and manufacturer’s details.
5. Include cavity and joint details: Fire test specimens must reflect actual cavity, flashing, termination and ventilation details; failure to represent these often leads to non-compliance. Include representative openings such as required holes or inspection access if referenced by the testing protocol.
6. Record thermocouple locations and 300°C criterion: Where timber interface protection is claimed, tests must measure interface temperature and record time above 300°C using thermocouples in the locations specified in S10C4; keep full test reports for the compliance audit trail.
7. Plan for maintenance and changes: Any alteration to cladding, penetrations, or service penetrations can change the tested performance; retain tested-system documentation and consult a certifier before retrofits or repairs.

Citations: NCC 2022 Volume One - Section C (C1, C2, C1V3, C2D11-C2D15), Specification 3 (S3C1-S3C6), Specification 10 (S10C4-S10C6); NCC 2022 Volume Two - State Schedule inserts (e.g., VIC A2G2(5)). Testing standards: AS/NZS 1530.3 and AS 1530.4. Structural and fixing standards referenced where relevant: AS 1684, AS 4100, AS 3700.

Note: This article summarises NCC and test-method requirements-jurisdictional schedules and local regulatory practice can change outcomes for specific projects. Verify requirements against the current NCC Volume One and the state schedule that applies to the project, and consult a registered building certifier for complex or ambiguous cases.