Defendable Space and Asset Protection Zone Requirements

What This Requirement Covers

Defendable space and Asset Protection Zone (APZ) requirements set minimum land and vegetation management measures around a building to reduce bushfire intensity, ember attack and radiant heat exposure. These requirements exist to increase the chance that a building can be defended, to reduce the likelihood of structure ignition from external fire, and to protect occupants, fire-fighting operations and adjoining assets. They apply where a site is in a designated bushfire prone area or otherwise subject to a Bushfire Attack Level (BAL) assessment under AS 3959 and planning instruments.

The rules are primarily used by designers, certifiers, planners, builders and homeowners when designing, approving or constructing buildings in the urban-bushland interface or other bushfire-exposed locations. In practice the APZ/defendable space requirement is implemented by a combination of the NCC (including state schedules), AS 3959 (Construction of buildings in bushfire-prone areas), and relevant state or local bushfire planning documents (for example Planning for Bushfire Protection), which together determine the required separation distances, vegetation management and any additional construction measures linked to BAL ratings.

Key Requirements

1. Asset Protection Zone (APZ) - an APZ is a cleared or managed area surrounding a building designed to reduce bushfire intensity. Typical APZ widths are described in state planning guidance and AS 3959 inputs to BAL assessment rather than a single NCC clause. Where APZs are referenced in NCC or state schedules, compliance may be required by local planning conditions or by modification of NCC deemed-to-satisfy provisions (see state notes below).
2. Bushfire Attack Level (BAL) - the required building construction standard depends on the assessed BAL (BAL-Low, BAL-12.5, BAL-19, BAL-29, BAL-40, BAL-FZ) as determined in accordance with AS 3959-2018 Construction of buildings in bushfire-prone areas and relevant state planning guidance (for example Planning for Bushfire Protection). The BAL determines ember, radiant heat and flame exposure levels and therefore APZ expectations used in design and planning.
3. Vegetation separation distances and fuel loads - AS 3959 and state guides give vegetation clearing and fuel load assumptions used in BAL calculations. APZ widths commonly used in planning guidance are in the order of 10 m to 100 m depending on slope and fuel type - for example an APZ of 10 m to 30 m is often cited as a minimum managed zone for many dwellings but larger APZs are required where fuel loads, slope or proximity to extensive bushland increase fire intensity. Exact dimensions and fuel management treatments must be determined by the BAL/site assessment.
4. Construction requirements linked to APZ/BAL - Construction standards for walls, roofs, windows, eaves, decks and external joinery change with BAL and refer directly to AS 3959-2018. For example:
5. BAL-12.5 and above: increased ember protection measures to glazing and external openings, restrictions on combustible cladding in certain areas, and ember-proofing of roof and guttering in accordance with AS 3959.
6. BAL-29/BAL-40/BAL-FZ: progressively more stringent requirements for non-combustible materials and higher levels of ember and radiant heat resistance as specified in AS 3959.
7. Water supply and access - many state provisions and NCC clauses require that sites in bushfire prone areas have vehicular access to enable firefighting and access to a sufficient water supply for firefighting purposes (for example a dedicated static water supply or hydrant), referenced in the NCC: see NCC Volume One provisions that require vehicular access and adequate water for firefighting where bushfire risk is relevant (for example NSW G5P2 and related S43C11 replacement language). Specifics (volumes, hydrant spacing) are set out in relevant state schedules and Australian Standards where adopted.
8. Relevant NCC clauses and other references
9. NCC Volume One - Part G5 and associated Deemed-to-Satisfy or state-modified provisions addressing construction in designated bushfire prone areas (see for example NSW G5D2, NSW G5D3, NSW G5P2, and S43C clauses when applicable). See notes in NCC Volume One that reference AS 3959 and state schedules.
10. NCC Volume Two - bushfire provisions for housing and references to BAL in housing provisions (see H7D4 and state inserts for application of BALs in Volume Two).
11. AS 3959-2018 Construction of buildings in bushfire-prone areas - primary Australian Standard for BAL assessment and construction details tied to BAL level.
12. Planning for Bush Fire Protection (PFPP) - where adopted by a state (notably NSW), PFPP procedures determine APZ widths, vegetation management and how BAL and APZ are applied to development consents.
13. ABCB Housing Provisions - may be referenced for housing-related application and state-adopted amendments.

Residential vs Commercial

1. Residential (Class 1 and Class 10):
2. Requirements for detached houses, townhouses and ancillary buildings are generally managed through NCC Volume Two, AS 3959 BAL assessments and state planning rules. Deemed-to-Satisfy provisions in Volume Two and the ABCB Housing Provisions may apply, but where a site is in a designated bushfire prone area the BAL assessment under AS 3959 and any state schedule adjustments determine required APZ and construction details (see H7D4 and state inserts). Typical APZs for residential properties used by many jurisdictions start at 10 m for low fuel scenarios but often require 20 m or more depending on slope and vegetation.
3. Commercial and other classes (Class 2-9):
4. For Class 2-9 buildings the relevant provisions are in NCC Volume One (Part G5 and S43 for special cases). Class 2, 3, 4 parts and some Class 9 buildings in designated bushfire prone areas are required to comply with AS 3959 or the applicable state variant; where Deemed-to-Satisfy provisions do not apply (for example for higher BALs or certain building types), a Performance Solution may be required (see NSW G5P2). Access, firefighting water and fire engineering considerations (e.g., occupant tenability, structural effects and firefighting access) receive greater emphasis for commercial/assembly or large occupancy buildings.

Exceptions and Exemptions

1. State planning authorities may vary APZ or BAL-derived requirements via development consent conditions, particularly where a bushfire safety authority has provided advice or approval (for example NSW RFS approvals under the Environmental Planning and Assessment Act). See NSW G5D3/G5P2 where AS 3959 may be modified by development consent following consultation with authorities.
2. Some small ancillary structures (subject to local thresholds for size or separation) may be exempted from full BAL construction requirements under local planning rules - check state schedules and local planning instruments. However where a Class 10a building or deck is immediately adjacent to a bushfire-exposed building it may still be captured by the bushfire provisions (see NSW G5D2 application list).
3. If a BAL assessment results in BAL-Low, some jurisdictions or Deemed-to-Satisfy paths may apply simplified or no specific construction changes; however state schedules may still require minimum APZ or vegetation management actions.
4. Alternative solutions (Performance Solutions) are permitted where Deemed-to-Satisfy provisions are not appropriate - these must demonstrate compliance with the relevant Performance Requirements in NCC Volume One (for example NSW G5P2) and typically require expert bushfire engineering, documented BAL justification and possibly consultation with the state bushfire authority.

State and Territory Variations

1. Each state and territory may modify national provisions by schedule in the NCC. Notable variations include:
2. New South Wales - NSW replaces or modifies several clauses: NSW G5D2, NSW G5D3, NSW G5P2 and sections of Specification 43 (S43C) to require AS 3959 with PFPP amendments and to permit modification by development consent and consultation with the NSW Rural Fire Service. NSW commonly requires APZ and construction in accordance with PFPP for sites assessed beyond BAL-12.5 (see NCC Volume One, NSW inserts).
3. South Australia - state inserts into NCC Volume One/Two set default BALs in some planning zones and identify distances for urban interface (see SA inserts in H7D4/G5D5).
4. Victoria, Queensland, Western Australia, Tasmania and the territories - each jurisdiction applies AS 3959 plus local planning guidance (e.g., CFA guidelines in Victoria, QFES guidance in Queensland, Planning for Bushfire documents where adopted) and may set APZ/fuel management distances in local planning schemes. Always check the relevant state schedule in NCC 2022 Volume One (Schedules 4-12) and local planning instruments.
5. Note: the NCC states explicitly that state and territory schedules may modify, add to or replace national provisions; always verify the applicable state schedule and local bushfire planning documents.

Practical Compliance Tips

1. Start with a professional BAL assessment - commission an AS 3959-compliant BAL site assessment early in design to define the required APZ and construction details rather than assuming a default distance.
2. Don’t assume a 10 m APZ is sufficient - while small APZs are commonly quoted, slope, fuel type and neighbouring vegetation often require wider APZs (20 m+). Use the BAL assessment outputs to set the correct width.
3. Link APZ actions to construction choices - select wall, roof and glazing materials consistent with the building’s BAL rating as specified in AS 3959-2018 so site vegetation management and construction work together.
4. Confirm state schedule variations - before lodging for approval, check the relevant NCC state schedule (NCC Volume One Schedules) and local planning requirements, for example NSW RFS or state CFA guidance may alter APZ or construction expectations.
5. Document water supply and access - ensure the site provides required vehicular access and firefighting water (static tank, hydrant or supply) in accordance with the applicable NCC/state provisions and local fire authority requirements; record volumes and access dimensions in the planning submission.
6. Manage combustible elements close to the building - ember traps like open eaves, subfloor voids, roof gutters and timber decking are common failure points; ember-proofing gutters, shielding eaves and using non-combustible decking adjacent to the building reduces risk.
7. Use a performance solution where appropriate - if Deemed-to-Satisfy provisions are impractical, prepare a bushfire Performance Solution using qualified bushfire consultants and refer to the relevant NCC Performance Requirements (for example NSW G5P2) and the supporting state bushfire authority advice.

Sources and references: NCC 2022 Volume One - Building Code of Australia (Part G5 and state inserts such as NSW G5D2/G5D3/G5P2 and Specification 43 replacements), NCC 2022 Volume Two (H7D4 and state inserts), AS 3959-2018 Construction of buildings in bushfire-prone areas, and Planning for Bush Fire Protection where adopted by states. Always verify the applicable state schedule in NCC 2022 Volume One and any local planning instruments for site-specific requirements.