Research has been carried out by the Local Councils throughout Western Australia to determine areas at risk of bushfires. The Building Code of Australia 2012 Part 220.127.116.11 Bushfire Areas states that it is a requirement of AS3959 ‘Construction of Buildings in Bushfire –Prone Areas’, that that any residential development located within a designated bushfire prone area must meet the minimum construction standards pertaining to the applicable BAL rating:
There is insufficient risk to warrant specific construction requirements
Increasing levels of ember attack and burning debris ignited by windborne embers together with increasing heat flux between 12.5 and 19 kWm2
Increasing levels of ember attack and burning debris ignited by windborn embers together with increasing heat flux between 19 and 29kw m2
Increasing levels of ember attack and burning debris ignited by windborne embers together with increasing heat flux with the increased likelihood of exposure to flames
Direct exposure to flames from fire front in addition to heat flux and ember attack
WHY IS A BAL ASSESSMENT REQUIRED?
The new legislation is primarily aimed at improving the ability of buildings in designated bushfire prone areas to better withstand attack from bushfire, therefore giving better protection to the building occupants, as well as to the building itself.
A BAL assessment is a means of measuring the severity of a building’s potential exposure to ember attack, radiant heat and direct flame contact. It is the basis for establishing the requirements for construction to improve protection of building elements from attack by bushfire.
WHAT DOES THE ASSESSMENT INVOLVE?
WHAT THE REPORT INCLUDES:
Site assessment and Nearmap image - this shows the proposed building site together with the surrounding vegetation. It shows the distance to the vegetation and the direction in which the photos, included within the report, were taken from site.
Vegetation classification and effective slope assessment - Shows photos of the vegetation within 100 meters of the site together with the classification of the vegetation and a measurement of the slope on which the vegetation sits.
Relevant fire danger index – shows the fire danger index (FDI) for the site.
Bushfire attack level assessment for each area of vegetation – indicates the BAL rating for each area of vegetation within 100 meters of the site
Determination of the appropriate construction requirements – provides the overall BAL rating for the site and outlines the sections of the standard that apply to the construction of the dwelling.
Proposed site plan – shows the areas of the dwelling that may be shielded from the predicted radiant heat levels and therefore may have a lower BAL resulting in less stringent building adjustments.