Class 9a buildings are only required to be protected against bushfire spread by the BCA in NSW (see relevant state legislation and planning policies for bushfire protection of Class 9a buildings in other states and territories).

Introduction

Australia contains some of the most hazardous bushfire areas in the world and concern over the loss of life and property led the BCA regulating the protection of buildings under Part G5.

Buildings that include residential components and occupants who require evacuation assistance such as Class 9a hospitals and nursing homes are of particular concern as they are considered to present a high level risk to life and personal property.

A building constructed in a designated bushfire prone area is to provide a resistance to bushfires in order to reduce the danger to life and minimise the risk of the loss of the building.

This is achieved by providing measures to improve the performance of structures subjected to radiant heat and possible flame contact as well as for burning debris.

Building requirements

To reduce the risk of ignition from a bushfire front while it passes a Class 9b building in a designated bushfire prone area must be constructed so as to satisfy the requirements of

• Part G5 of the Building Code of Australia (BCA)
• AS 3959-1999 “Construction of buildings in bushfire-prone areas”

State Variations

New South Wales contains state variations to Part G5 of the BCA. In summary:

• NSW Part G5 extends the requirements to certain Class 9 buildings that are considered to be a higher risk such as those housing the elderly or disabled. These higher risk buildings are referred to as a special fire protection purpose buildings (see definition at the end of this document).
• NSW G5.2 requires the “Site Bushfire Attack Assessment” under AS3959 be replaced by an alternate method of assessment and incorporated into the integrated development process that forms part of any development consent (see NSW G5.2 for full details)
• Other states do not require Class 9 buildings be treated against bushfire threat under Part G5 of the BCA.

Alternative Solutions

If any of the above requirements cannot be met either because of innovative development or there is a particular construction issue, the building would not comply the Deemed-to Satisfy Requirements of the Building Code of Australia and consequently a Construction Certificate or an Occupation Certificate will not be able to be issued.

To overcome this situation the an Alternative Solution may be able to be prepared in accordance with Clause A0.8, A0.9, & A0.10 of the BCA, demonstrating that the method of construction will satisfy the Performance Requirement GP5.1:

• Providing evidence that the form of construction satisfies the BCA;
• Using a Verification Method;
• Comparison with the Deemed-to-Satisfy provisions
• Expert judgement (such as a Bushfire Consultant).

General Deemed-to-satisfy Requirements

To satisfy the Deemed-to-Satisfy provisions of the BCA with respect to bushfire protection, the designer must ascertain:

• Is the Class 9a building located in NSW? (the only state requiring Class 9a buildings be protected under Part G5 of the BCA.
• Is the Class 9a building considered a special fire protection purpose (see definition at the end of this document)?
• Is the Class 9a building in a designated bushfire prone area? Meaning that the land is nominated under legislation (or identified under an environmental planning instrument, development control plan, or in the course of processing and determining a development application in NSW)
•  

Should the designer answer “yes” to each of the above, the building must comply with the provisions of AS3959 as detailed below.

Bushfire Requirements under AS3959

Where a building is required to be constructed so as to offer protection in the event of a bushfire the designer must refer to AS 3959, and construct the building to satisfy the risk category.

There are three levels of construction in bushfire prone areas depending on the level of risk, namely;

• Level 1 Construction for the category of medium bushfire attack
• Level 2 Construction for the category of high bushfire attack
• Level 3 Construction for the category of extreme bushfire attack 

Framed external walls must either incorporate a breather-type sarking complying with AS/NZS 4200.1 and with a flammability index of not more than 5 installed immediately behind the external cladding or an insulation material conforming to the appropriate Australian Standard for that material.

External doors in must be fitted with weather strips or draught excluders to prevent the penetration or build-up of burning debris beneath the door;

Roof & wall junctions must be sealed either by the use of fascias and eaves linings or by sealing the gaps between the rafters with a suitable non-combustible material.

Roof sarking must have a flammability index of not more than 5. Tiled roofs must be fully sarked with the sarking located directly below the tiling battens so as to cover the entire roof area including the ridge.

For sheet roofing all gaps under the corrugations, capping or ribs of the roofing material where it meets the fascia or wall line must be sealed or protected either by fully sarking the roof or by providing corrosion-resistant steel or bronze mesh, with a maximum aperture size of 1.8 mm, profiled metal sheet, neoprene seal, compressed mineral wool or similar material.

It should be noted that where compressed mineral wool is used for sealing against bushfire attack adequate ventilation should be provided to stop condensation on the mineral fibre causing corrosion in the roof sheeting or supporting structure.

Where rooflights are proposed to be installed all penetrations of the roof space for the installation of rooflights and associated shafts must be sealed with a non-combustible sleeve or lining.

All components of roof ventilators, including the rotary type, must be constructed of non-combustible material and sealed against the entry of sparks and embers with corrosion-resistant steel or bronze mesh having a maximum aperture size of 1.8 mm

Learn More

Class 9a BCA Acoustic Requirements
Class 9a BCA Fire Requirements

Class 9a BCA Thermal Requirements

Definitions

Certificate of Accreditation
A Certificate of Accreditation is issued by a State or Territory accreditation authority and is evidence that a building material, method of construction or design (subject to any specified conditions or limitations) is accepted within that State or Territory as complying with the BCA. Certificates of Accreditation are no longer issued by the ABCB. Certificates issued by the ABCB under the previous scheme are no longer valid.

Certificate of Conformity
A Certificate of Conformity issued under the ABCB scheme is evidence that a building material, method of construction or design (subject to any specified conditions or limitations) is accepted within all States and Territories as complying with the BCA.

Combustible
A test done in accordance with AS 1530.1 will determine if a material is combustible. If materials used in an assembly contain combustible components, then the assembly is combustible.

Designated bushfire prone area means land which has been designated under a power of legislation as being subject, or likely to be subject, to bushfires.

Designated bushfire prone area (NSW Definition Only) means land that:

• has been designated under legislation; or
• has been identified under an environmental planning instrument, development control plan or in the course of processing and determining a development application, as land that can support a bushfire or is likely to be subject to bushfire attack.

   
Fire-resisting
Applies to fire-resisting building elements, including structural members and non-loadbearing components, such as cladding, doors, windows and the like.

Flammability Index
A test performed in accordance with AS 1530.2 will determine the flammability index of a material.

Insulation
Insulation is the third criterion used when specifying an FRL.

Integrity
Integrity is the second criterion used when specifying an FRL. See example under “insulation” definition.
The test under AS 1530.4 considers that a building element has failed the integrity criterion when either the element collapses, or the element develops cracks, fissures or other openings through which flames or hot gases can pass.

Non Combustible
Clause C1.12 of the BCA lists materials deemed to be non-combustible. These materials may be used wherever a material is required to be non-combustible. In some instances the material may contain combustible components. The materials listed are not intended to apply to fire place hearths.
The following materials, though combustible or containing combustible fibres, may be used wherever a non-combustible material is required:

1. Plasterboard.
2. Perforated gypsum lath with a normal paper finish.
3. Fibrous-plaster sheet.
4. Fibre-reinforced cement sheeting.
5. Pre-finished metal sheeting having a combustible surface finish not exceeding 1 mm thickness and where the Spread-of-Flame Index of the product is not greater than 0.
6. Bonded laminated materials where—
7. Each laminate is non-combustible; and
8. Each adhesive layer does not exceed 1 mm in thickness; and
9. The total thickness of the adhesive layers does not exceed 2 mm; and
10. The Spread-of-Flame Index and the Smoke-Developed Index of the laminated material as a whole does not exceed 0 and 3 respectively.

Special fire protection purpose (NSW Definition Only) (as per Section 100B(6) of the Rural Fires Act, 1997, means any of the following purposes:
a school, (for application of this definition in the BCA, the term “school does not include a college, university or similar tertiary educational establishment)

1. a child-care centre
2. a hospital (including a hospital for the mentally ill or mentally disordered),
3. a hotel, motel or other tourist accommodation,
4. a building wholly or principally used as a home or other establishment for mentally incapacitated persons,
5. housing for older people or people with disabilities within the meaning of State Environmental Planning Policy No.5 – Housing for Older People or People with a Disability (now SEPP Seniors Living)
6. a group home within the meaning of State Environmental Planning Policy No.9 – Group Homes
7. a retirement village,
8. any other purpose prescribed by the regulations (Rural Fires  Regulation 2002)

Spread-of-Flame Index
A test in accordance with AS/NZS 1530.3 determines the Spread-of-Flame Index of a material. The index is based on a logarithmic scale of 0 to 10. A lower index number indicates better performance.

Standard Fire Test
AS 1530.4 contains details of the Standard Fire Test. The test is used to determine the FRL of a building element. The results are recorded in order as: structural adequacy, integrity and insulation.

Verification Method means a test, inspection, calculation or other method that determines whether a Building Solution complies with the relevant Performance Requirements.