AUST – HENDRY building surveyors often have to explain to clients how the Building Code of Australia (BCA) determines fire safety provisions relative to their building. This article provides a broad overview which will help non professionals in their understanding of the BCA.
1. Use of building under the BCA
Buildings are designed to be used for different purposes. For example, some buildings are designed to be used for residential purposes i.e. buildings where people sleep, and other buildings are designed to be used for commercial or industrial purposes i.e. buildings where people work. The fire safety requirements in the BCA clearly reflect the fact that people need more protection from fire in buildings where they may be asleep when a fire starts. An example of this is the egress requirements in BCA Volume One, Part D1 where there are special requirements for Class 2 and 3 buildings as distinct from the requirements for Class 5 to 9 buildings.
Fire safety requirements in the BCA also take into consideration the nature of the occupants likely to be using the building. For example provisions would be affected by such considerations as whether the building occupants are likely to be sick or disabled or unfamiliar with the building.
3. Fire load of building
The nature of the process or task being performed in the building can affect fire safety requirements nominated under the BCA. For instance, the fire load of a building used as an office where “paperwork” is the principal task would be much less than a factory where a high hazard process such as the manufacture of paint is being undertaken.
Note the above 3 aspects i.e. use of building, nature of occupants and fire load of building are the principal factors in determining the 10 classes of buildings as set out in BCA Volume One.
4. Height of building
The taller the building the greater are the likely problems relating to:
– egress from the building; and
– exposure hazard.
The effective height of a building in these instances is therefore only related to finished ground level under the BCA. The taller the building the greater the vertical distance of egress travel to the safety of finished ground level outside the building (which must of course be directly connected to a street).
The following illustration from BCA Illustrated depicts the requirements for the establishment of the effective height for a building . (Please note the ‘Issue’ and ‘Explanation’ not included).
Also the taller the building above finished ground level, the greater is its exposure hazard to and from neighbouring buildings.
The concept of “rise in storeys” in the BCA is derived from these considerations and is therefore related to height of building above finished ground level. It is therefore a term generally applied to fire safety considerations.
The concept of “number of storeys contained” under the BCA in a building must not be confused with “rise in storeys’ as it is usually based on the total number of storeys in the building – including those below ground level, and is generally applied to structural considerations.
5. Passive (inbuilt) protection of building
The materials such as steel, concrete or timber, used in the construction of the building can affect the fire and safety requirements.
The term fire-resistance level (FRL) defined in BCA Volume One, Clause A1.1 (and BCA Volume Two, Part 1.1) means the fire-resistance grading period determined according to the “Standard Fire Test” Which is a fire resistance test of structures as set out in AS1530.4-2005 Methods for fire tests on bounding materials, components and structures – Fire resistance test of elements of construction or as otherwise determined according to Specification A2.3.
FRLs which are expressed in terms of 3 criteria under the BCA i.e. structural adequacy, integrity and insulation (all of which are defined in Clause A1.1) allow for more accurate and meaningful stipulation of control e.g. columns only need to be structurally adequate – hence a requirement of 60/-/-. Windows however, must simply maintain some integrity – hence a requirement of -/60/-. FRLs are expressed in minutes.
6. Active protection of building
The use of fire services such as sprinkler systems, fire hose reels and fire extinguishers are the final aspects that can affect the fire safety requirements. These are playing a much more important role nowadays and are used as trade-offs against the passive protection items listed above.
The BCA is being gradually amended to recognise this change in emphasis. Furthermore the essential safety measures inspections and maintenance provisions in most State Regulations assist in ensuring that such systems remain reliable if and when required.
Building Legislation Table
Refer to our Building Legislation table for further information on the building control process.