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Part G5 Construction in bushfire prone areas
Performance Requirements
GP5.1 Bushfire resistance
A building that is constructed in a designated bushfire prone area must, to the degree necessary, be designed and constructed to reduce the risk of ignition from a bushfire, appropriate to the—
(a)
potential for ignition caused by burning embers, radiant heat or flame generated by a bushfire; and
(b)
intensity of the bushfire attack on the building.
Application
Application
GP5.1 only applies to—
- a Class 2 or 3 building; or
- a Class 10a building or deck associated with a Class 2 or 3 building,
located in a designated bushfire prone area.
The Objective of this Part is to—
(a)
safeguard occupants from injury; and
(b)
protect buildings,
from the effects of a bushfire.
Application
Application
GO5 only applies to—
- a Class 2 or 3 building; or
- a Class 10a building or deck associated with a Class 2 or 3 building,
located in a designated bushfire prone area.
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.
Application
Application
GF5.1 only applies to—
- a Class 2 or 3 building; or
- a Class 10a building or deck associated with a Class 2 or 3 building,
located in a designated bushfire prone area.
GP5.1 applies only to a Class 2 or Class 3 building, or a Class 10a building or deck associated with a Class 2 or 3 building in a designated bushfire prone area.
The basis of GP5.1 is that:
- bushfires provide a major risk of ignition to a building that may be caused by burning embers, radiant heat and flame; and
- the design and construction measures required to deal with this risk is associated with the mechanism of attack and its intensity.
Verification Methods
GV5 Buildings in bushfire prone areas
(a)
Compliance with Performance Requirement GP5.1 is verified if the ignition probability for a building exposed to a design bushfire does not exceed 10%.
(b)
Bushfire design actions must be determined in consideration of the annual probability of a design bushfire derived from—
(i)
assigning the building or structure with an importance level in accordance with GV5(c); and
(ii)
determining the corresponding annual probability of exceedance in accordance with Table GV5.1.
(c)
A building or structure's importance level must be identified as one of the following:
(i)
Importance level 1 — where the building or structure presents a low degree of hazard to life and other property in the case of failure.
(ii)
Importance level 2 — where the building or structure is not of importance level 1, 3 or 4 and is a Class 2 building accommodating 12 people or less.
(iii)
Importance level 3 — where the building is designed to contain a large number of people and is a—
(A)
Class 2 building accommodating more than 12 people; or
(B)
Class 3 boarding house, guest house, hostel, lodging house or backpackers accommodation; or
(C)
Class 3 residential part of a hotel or motel; or
(D)
Class 3 residential part of a school.
(iv)
Importance level 4 — where the building or structure is—
(A)
essential to emergency management or post-disaster recovery; or
(B)
associated with hazardous facilities; or
(C)
subject to a necessary 'defend in place' strategy and is a—
(aa)
Class 3 accommodation building for the aged, children or people with disabilities; or
(bb)
Class 3 residential part of a health-care building which accommodates members of staff; or
(cc)
Class 3 residential part of a detention centre; or
(dd)
Class 9a or 9c building; or
(ee)
building that operates in the event of a bushfire emergency, such as a public bushfire shelter or a bushfire emergency control centre.
Table GV5.1 Annual Probability of Exceedance (APE) for design bushfire actions
| Importance level | Complex analysis APE for bushfire exposure | Simple analysis APE for weather conditions (design bushfire) |
|---|---|---|
| 1 | No requirement | No requirement |
| 2 | 1:500 | 1:50 |
| 3 | 1:1000 | 1:1000 |
| 4 | 1:2000 | 1:2000 |
Note to Table GV5.1: Complex analysis must consider the probability of ignition, fire spread to the urban interface and penetration of the urban interface coincident with fire weather conditions.
(d)
The ignition probability for a building must be assessed by application of the following:
(i)
An event tree analysis of relevant bushfire scenarios.
(ii)
Design bushfire conditions that include combinations of the following actions appropriate to the distance between the building and the bushfire hazard:
(A)
Direct attack from airborne burning embers.
(B)
Burning debris and accumulated embers adjacent to a building element.
(C)
Radiant heat from a bushfire front.
(D)
Direct flame attack from a bushfire front.
(e)
Applied fire actions must allow for reasonable variations in—
(i)
fire weather; and
(ii)
vegetation, including fuel load, burning behaviour of vegetation (including the potential for crown fires); and
(iii)
the distance of the building from vegetation; and
(iv)
topography, including slopes and features that may shield; and
(v)
ignition of adjacent buildings, building elements, plants, mulch and other materials; and
(vi)
effective size of fire front; and
(vii)
duration of exposure; and
(viii)
flame height; and
(ix)
flame tilt; and
(x)
flame adhesion to sloping land; and
(xi)
the height of the building and its elements.
(f)
The assessment process must include consideration of—
(i)
the probability of non-complying construction of critical aspects of an approved design; and
(ii)
the probability of critical aspects of an approved design being fully functional during the life of the building; and
(iii)
inclusion of safety factors; and
(iv)
sensitivity analysis of critical aspects of a proposed design.