Building Construction and Design
Building construction and design is another aspect that must be considered when building on bush fire prone land. To determine the required level of construction for your proposal see the site assessment methodology contained within Planning for Bush Fire Protection 2006. Alternatively, the Single Dwelling Application Kit can be used.
There are five categories of bush fire attack that are used to determine the appropriate level of construction to be applied to a development:
- low
- medium
- high
- extreme
- flame zone.
The categories of attack are determined by:
- The type of vegetation
- How close your building is to the vegetation
- What the effective slope is (i.e. fire runs more readily and with greater intensity uphill).
- The Fire Danger Index applicable to the region
The building requirements for house design and construction vary according to the category of bush fire attack that a development falls into. The building requirements for each level of construction are set out in Australian Standard: 3959 Construction of buildings in bushfire-prone areas 1999 (AS3959). A full version of this document can be purchased from Standards Australia with an abridged version available in the publications section of this website. The 3 levels of construction detailed in this document are:
- Level 1 construction
- Level 2 construction
- Level 3 construction
The various categories and bush fire attack and the associated construction requirements are outlined below.
Low
Minimal attack from radiant heat and flame due to the distance of the site from the vegetation, although some attack by burning debris is possible. There is insufficient threat to warrant specific construction requirements, but residents should still do basic property preparation.
Medium
Attack by burning debris is significant with low levels of radiant heat (not greater than 12.5kW/m2). Radiant heat is unlikely to threaten building elements (i.e. unscreened glass). Specific construction requirements for ember protection and accumulation of debris are warranted (Level 1 construction standards).
High
Attack by burning debris is significant with an increased radiant heat levels (not greater than 19kW/m2) threatening some building elements. Specific construction requirements for protection against embers and radiant heat are warranted (Level 2 construction standards).
Extreme
Attack by burning debris is significant and radiant heat levels (not greater than 29kW/m2) can threaten building integrity. Specific construction requirements for protection against embers and higher radiant heat are warranted. Some flame contact is possible (Level 3 construction standards).
Flame Zone
Radiant heat levels will exceed 29kW/m2. Radiant heat levels and flame contact are likely to significantly threaten building integrity and result in significant risk to residents who are unlikely to be adequately protected. The flame zone is outside the scope of AS3959 and the NSW Rural Fire Service will recommend protection measures in addition to minimum Level 3 construction where the applicant does not provide an adequate performance solution. Other measures such as drenching systems, radiant heat barriers and fire rated glass may also be required.
In preparing a development application under section 79BA, an applicant may consider the provision of higher-level construction standards as a level of equivalence for the inability to provide the required APZ. Consideration may also be given to additional measures such as drenching systems, radiant heat shields and shutters to satisfy the performance criteria.
The performance criteria and acceptable solutions for building construction and design can be found in Chapter 4 - Performance Based Controls (PDF 20,901kb).
For more information about each of the six bush fire protection measures to be considered when planning a development in a bush fire prone area, return to the Bush Fire Protection Measures main page.
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