Bush fire zone building!

As we are in a fire zone ( a block in the middle of a Karri forest basically ) there are certain requirements relating to house construction.

Apart from the usual planning, building and health approvals, we were also required to assess the degree of fire risk at our property before we could obtain a building license.

This involved getting a copy of the Australian Standard AS3959 ( Construction of buildings in fire prone areas ) and using the procedure outlined to make an assessment. This then needed to be submitted to the local shire council building inspector who then completes his own assessment and makes a final decision as to the level of construction required.

The following will give you some idea of what was required.

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

Depending on the outcome of the assessment there are Level 1, 2 or 3 construction requirements.

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.

I assessed our block at level 3 but the building inspector was so impressed with the clearing we had done that he assessed it at Level 2.

The details required for each level of construction are well described in the following brochure produced by ACT Planning and Land Authority.