Specification C1.1 Fire-resisting construction

Refer to the definition in Schedule 3 on the term “fire-source feature”.

A fire-source feature is a possible fire-source external to the building from which fire could spread into the building. It may be an allotment boundary or another building on the allotment from which fire could spread to the subject building.

Clause 2.1 does not consider a building element to be exposed to a fire-source feature if it is shielded from the fire-source feature by another part of the building which:

• has an FRL of 30/–/– or more, and is not transparent or translucent;
• is less than 15 metres above another building on the allotment. Parts of a building more than 15 metres above another building are not deemed to be affected by fire; or
• is below the level of the finished ground at every relevant part of a side or rear boundary.

Figure Spec C1.1(1) illustrates some of the exemptions from the exposure to a fire-source feature.

Figure Spec C1.1(1) Part of a building not exposed to a fire-source feature

The building element must have an FRL required for the closest part of the element exposed to the fire-source feature (see Clause 2.1(c)(i)).

Alternatively, the building element may have a varying FRL according to the individual distance of each section of the building element from the fire-source feature (see Clause 2.1(c)(ii)).

Figure Spec C1.1(2) illustrates the alternatives for an external loadbearing wall of a Class 5 building required to be of Type A construction.

Clause 2.2(a) sets out the requirements for the fire protection of building elements that provide lateral or vertical support to another building element. This is because a building element with an FRL is usually dependent on the support to maintain its FRL.

Accordingly, Clause 2.2(a) does not apply to elements that support ceilings required to have a fire-protective covering or a resistance to the incipient spread of fire. Nor to an element required to be non-combustible.

Clause 2.2(b) lists a number of exemptions to Clause 2.2(a)(ii) and (a)(iii)(B).

The lateral support for the types of wall referred to in Clause 2.2(b)(i) is considered unnecessary in these cases, because Clause 5.1(b) allows the use of brick veneer walls, and C1.11 enables the prevention of outward collapse of certain external walls by specifying the connection of panels to the building's frame.

The inherent fire resistance of the supports included in Clauses 3 . 9, 4.2 and 5.2 is considered adequate in the carparks covered by each clause. It should be noted that compliance with the relevant Table is necessary in order to comply with the relevant clause.

Clause 2.2(b)(iii) exempts roofs providing lateral support to other building elements. This is because of a concession within Clause 3.5 for Type A construction. In addition, there is no requirement for Type B and C construction, principally because such buildings are generally low rise.

Clause 2.2(b)(iv) exempts certain columns, as listed in Clause 2.5, from having an FRL.

Under Clause 2.2(b)(v) a fire wall or fire-resisting wall referred to should not collapse because it is supported by another building element on the other side of the wall.

Figure Spec C1.1(2) Plan showing alternative methods of complying with Table 3

A lintel must have the same FRL as the part of the building containing it. This is unless it does not contribute to the support of a fire door, fire window or fire shutter. Otherwise, the failure of the lintel during a fire could cause the collapse of all, or part, of the wall.

Clause 2.3 only applies to a lintel required by the Deemed-to-Satisfy Provisions to have an FRL.

Clauses 2.3(a) and (b) contain some concessions for small openings where the failure of the lintel would not result in a major collapse of the wall and lead to the spread of fire to another building.

Clause 2.4 prohibits a required FRL of a building part from being reduced by the attachment or installation of facings, finishes, ancillary elements or the installation of ducting or any other service.

The reason for controlling this is due to the potential for changes to the fire performance of a building element via attaching or installing another element.

The concessions contained in Clause 2.5(a) allow a steel column to not have an FRL in one and, in some cases, two storey buildings.

The basis for this concession is the low rise of such buildings. In many cases, the columns form the legs of a portal frame, with the roof being non-fire rated. In such a case, there would be little benefit in fire rating the column when the roof beams are not rated.

Because of the importance of the structural integrity of a common wall or fire wall in limiting the spread of fire, the concession for steel columns providing lateral support does not apply.

The concessions contained in Clause 2.5(b) permit a reduced FRL in timber columns in single storey buildings. One method of determining the FRL of a timber column is to use the charring rate of the type of timber in the column.

The structures on a roof referred to in Clause 2.5(c) are not likely to lead to the spread of fire, especially as they are required to be non-combustible. The intent of Clause 2.5(c)(ii)(E) is to specify that the concession does not apply to structures that contain units that in turn contain flammable or combustible liquids and gases.

The curtain walls referred to in Clause 2.5(d) must be non-combustible and protected by an external wall-wetting sprinkler system. When such construction is used, protection is provided from fire spreading to the subject building. For the term “curtain wall”, see Schedule 3. For the purposes of this provision, glass is regarded as non-combustible.

Balconies, verandahs and the like do not generally add a significant fire load to a building. Therefore, they are not required to be in compliance with Table 3, 4 or 5. This is provided that occupants are not put at risk during an evacuation because the only means of egress is by way of the balcony, verandah or the like.

Also, if the building is of Type A construction, the balcony, verandah or the like must be situated at a low level of the building, and have non-combustible supports.

The Clause 2. 6 concession does not apply to certain Class 9b buildings, as specified in Clause 2.6(a). The concession only applies to certain small mezzanines, as specified in Clause 2.6(b).

If it complies with the conditions specified in Clause 2.6(b), a mezzanine and its support may be constructed from materials that do not have an FRL and/or are combustible.

Table 2.6 requires an increase in each FRL criterion of each wall or column that supports any other part of the building, and is within 6 metres of the mezzanine. There is no case in which a building element, with an increased fire rating, requires an FRL greater than 240 minutes.

Increasing the FRLs surrounding a mezzanine which is combustible, or which does not have an FRL, recognises the increased fire load that exists within both the mezzanine and the storey as a whole. This recognises the fire load limiting effect of the minimum area requirement in Clause 2.6(b)(i).

Shaft enclosures required to be fire-resisting must be completely fire-separated from all other portions of the building by building elements that have the appropriate fire-resistance.

Clause 2.7 complements other requirements for the walls of shafts by requiring that shafts be enclosed at the top and bottom by fire rated construction.

Clause 2.7 grants exemptions for the top and bottom of shafts in cases where the likelihood of fire entering the shaft is unlikely. This occurs when the top of the shaft is the top of the building (see Clause 2.7(a)), or the bottom of the shaft is laid on the ground (see Clause 2.7(b)).

Part A6 classifies a storey used for carparking as Class 7. The fire risks of a single storey carpark in a low-rise Class 2 or Class 3 building are not as substantial as they are in other carparks attached to other classifications, so a concession is suitable. This concession is based upon the assumption that the carpark associated with the Class 2 or 3 building will be for the exclusive use of the building occupants and that the carpark would represent a low fire risk.

The sole purpose of this concession is to allow the carpark and/or ancillary use storey to be regarded as a Class 2 or Class 3 building, as applicable, for the purposes of determining the fire resistance requirements of Specification C1.1.

This concession applies to buildings which are otherwise wholly Class 2, wholly Class 3 or a mix of Class 2 and 3 and:

• the storey to which the concession is to apply is used only for carparking, or an ancillary purpose such as storage of normal household items (see Clause 2.8(a)(i) and (b)(i));
• in the case of Class 2 buildings, contain no more than 4 storeys (see Clause 2.8(a)(ii)); and
• in the case of Class 3 buildings or buildings that are a mix of Class 2 and 3, contain no more than 3 storeys (see Clause 2.8(b)(ii)).

The reason for the concession applying to an additional storey in Class 2 buildings is that the residents of these buildings are long term and are usually aware of the building layout and exit routes. This concept is consistent with D1.3.

The Clause 2.8 concession does not apply if the building contains any other classification of building.

“Residential care building” is defined in Schedule 3.

This concession is a response to concerns expressed by aged care organisations and health authorities in regards to the impact of certain regulatory requirements on the design and operation of aged care hostels and nursing homes.

The requirements for fire separation of individual sole-occupancy units (including self-closing doors) in aged care hostels was considered to impose unwarranted development costs.

Fire compartmentation and the installation of door closers was considered to be impractical in the daily use of an aged care facility. Self-closing fire doors are too heavy and difficult to operate by frail, elderly people. In a number of cases this resulted in the doors being wedged open, thus negating the fire separation.

The limitation of the Class 1b concessions to buildings having an area of 300 m² or less and 12 occupants or less (see A6.1) meant that those concessions could not be used for many aged care hostels. The concessions in Clause 2.9 are considered to be reasonable for the larger aged care hostels. In some States or Territories it is not acceptable for a Class 1b building to be used to house elderly people or other people who require special care.

The concession contained in Clause 2.9(a)(i) applies to the requirements for floors and loadbearing walls as set out in Tables 3, 4 and 5 of Specification C1.1. The concession, allowing a reduction in FRLs, is limited to where the wall is an internal wall. An external wall is not subject to this concession.

The concession contained in Clause 2.9(a)(ii) for non-loadbearing internal walls, allows a reduction in FRLs subject to several conditions outlined in Clause 2.9(a)(ii). The conditions outlined in Clause 2.9(a)(ii) must be achieved for the concession to apply. These conditions require walls to be:

• lined with 13 mm standard grade plasterboard, or a non-combustible material equivalent to 13 mm standard grade plasterboard (see Clause 2.9(a)(ii)(A)); and
• extend to the underside of the floor above, a ceiling lined with standard grade plasterboard not less than 13 mm thick or equivalent fire protective material, or a non-combustible roof covering. The wall height requirement aims to create a smoke proof wall. This aim requires that joints and the like be sealed to prevent the spread of smoke through potential cracks and openings (see Clause 2.9(a)(ii)(B)).

Clause 2.9(a)(ii)(C) requires that any insulation in a cavity in a non-loadbearing internal wall must be non-combustible. This is to limit the spread of fire by way of the wall cavity.

The mandatory use of non-combustible materials prohibits the lining of non-loadbearing internal walls with timber panelling. This does not restrict the use of timber mouldings and the like.

In addition to the above concessions for load bearing and non-load bearing walls, doors in a Class 3 building must still comply with the requirements of C3.11(d)(ii), and walls must still comply with the requirements of Part F5—Sound Transmission and Insulation.

Other provisions relating to residential care buildings are contained throughout the BCA. These include:

• C3.11(d)(ii), regarding construction bounding sole-occupancy units and public corridors;
• Clause 6(c) of Specification E2.2a, regarding warning systems; and
• Specification E1.5, regarding sprinkler systems.

Table 3 of Specification C1.1 sets out the required FRLs of building elements in a building required to be of Type A construction. The required FRL depends on whether the element is loadbearing or non-loadbearing, if the element comprises or is incorporated in an external wall, and its distance from any fire-source feature.

When using Table 3 of Specification C1.1 , it should be noted that Clause 6 of Schedule 5 permits the deletion of the structural adequacy criteria of an FRL for non-loadbearing elements. The reason for this is that if such an element fails during a fire, there will be no flow-on collapse of other elements. See definition of ‘loadbearing’ in Schedule 3 to assist in understanding this provision.

The surface of an occupiable outdoor area located on a roof should be treated as a floor for the purposes of Specification C1.1 .

Clause 3.1(a) requires building elements to achieve at least the FRLs set out in Table 3.

Clause 3.1(a) only applies to the building elements listed in Table 3, and any beams or columns incorporated in such building elements.

Clause 3.1(c) requires internal walls to extend to a barrier to stop or limit the spread of fire over the top of the wall. Clause 3.1(c) only applies to internal walls required to have an FRL with respect to integrity and insulation. This is consistent with the intent that the walls are only required to extend to the underside of a floor or roof, etc when the wall is required to perform a fire separating function.

Clause 3.1(d) requires loadbearing internal walls and loadbearing fire walls (in both cases, including those which are part of a loadbearing shaft) to be of concrete, masonry or constructed from fire-protected timber (however, fire-protected timber has certain limitations).

Internal columns can be exposed to a fire-source feature through a window in an external wall. Clause 3.1(f) requires such a column within 1.5 metres of a window to have the same FRL as an external column.

Clause 3.2 grants floors a number of concessions from the FRL requirement. The reason for each of the concessions is listed below:

• there is no fire load below a floor laid directly on the ground, (see Clause 3.2(a));
• there is a low fire load if the space below a Class 2, 3, 5 or 9 building is not a storey or does not contain the listed elements, (see Clause 3.2(b));
• the space below a stage would generally have a low fire load because it cannot be used as a dressing room, storage area, or the like. A fire in the storey below would not affect the stage because it is over a floor with the required FRL. In addition, the stage would not have a room below which might have a high fire load, (see Clause 3.2(c));
• the floor is within a residential sole-occupancy unit. This is because resistance to the spread of fire between sole-occupancy units only is required. The levels connected are within the one sole-occupancy unit and the spread of fire from one sole-occupancy unit to another would not be affected by the construction of an internal floor without the required FRL, (see Clause 3.2(d)); and
• no fire separation is required for an open-access floor as a fire in the storey below could not affect the area because it is over a floor with the required FRL, (see Clause 3.2(e)).

Generally, Class 5 and Class 9b buildings have a comparatively low fire load which can be further reduced if the structural carrying capacity of the floor (“live load” or “imposed action”) is restricted because there will be a lower likelihood of the building containing a high level of stored combustible materials. AS 1170.1 and AS/NZS 1170.1 allows certain areas within office (Class 5) and assembly (Class 9b) buildings to have design floor loads of 3 kPa.

In essence, the lower the structural carrying capacity of the storey’s floor, the lower the fire load. This lower fire load in turn permits a reduced FRL for the floor or roof above such a storey.

The philosophy of fire protection in this provision is that the fire load of a storey controls the FRL of the floor or roof above it. This is because a fire on one storey will affect the level above to a greater degree than itself.

Clause 3.3(a) sets out the concession for a floor above, and Clause 3.3(b) sets out the concession for the roof above.

Clause 3.4 allows a concession for a roof of non-fire-resisting construction to be superimposed above a concrete slab roof. Such roofs are usually used for weather protection reasons.

Clause 3.4(a) states that the superimposed roof and any supporting members must be non-combustible.

Clause 3.4(b) states that the concrete slab roof must comply with Table 3 of Specification C1. 1.

If compliance is achieved with the conditions outlined in Clause 3. 4, a concession is reasonable because a fire is unlikely to break through the concrete roof slab.

The roofs of certain types of buildings can be required to have an FRL to limit the spread of fire from the roof to another building, or from another building to the roof. Clause 3.5 grants a number of concessions by which certain roofs need not have an FRL, provided the roof covering is non-combustible.

In Clause 3.5(a), the BCA assumes that the specified sprinkler system will control any fire prior to it breaking through the roof.

In Clause 3.5(b), the BCA assumes buildings with a rise in storeys of 3 or less will comprise a comparatively low fire risk. Most buildings with a rise in storeys of 3 or less are permitted to be of Type B or Type C construction.

In Clause 3.5(c), the BCA assumes that Class 2 and Class 3 buildings have a relatively low fire load compared to other classifications, and recognises that the potential size of a fire in Class 2 and Class 3 buildings is limited by the bounding construction of the sole-occupancy units. This concession does not apply where another classification forms part of the storey immediately below the roof (eg a restaurant, which is Class 6).

Clause 3.5(d) assumes that the incipient spread of fire resistant ceiling will stop or limit the spread of fire to the roof space or roof of the building for sufficient time for it to be brought under control.

The roofs of certain types of building can be required to have an FRL, or to be of non-combustible construction, to limit the spread of fire from the roof to another building. This is particularly the case with a high rise building. Clause 3.6 specifies the requirements for such roof lights.

The requirements of Clause 3.6 aim to minimise the risk that fire will spread by way of roof lights:

• from another building on an adjoining allotment;
• to an adjoining sole-occupancy unit; or
• to an adjoining fire compartment or fire-separated part of the building.

Clause 3.6 facilitates this aim by minimising the:

• roof area which can be comprised of roof lights (see Clause 3.6(a));
• distance a roof light is from an allotment boundary (see Clause 3.6(b)(i));
• distance a roof light is from unprotected parts of the building which are higher than the roof (see Clause 3.6(b)(ii));
• distance a roof light is from roof lights or the like in adjoining sole-occupancy units, if the bounding walls are required to have an FRL (see Clause 3.6(b)(iii)); and
• distance a roof light is from any roof light or the like in adjoining fire-separated parts of the building (see Clause 3.6(b)(iv)).

In some cases, the BCA requires incipient spread of fire resistant ceilings to stop or limit the spread of a fire to the roof space.

Clause 3.6(c) provision requires that roof lights be installed in a manner which will maintain the requisite level of protection. This is an example of a “performance-type” provision within the Deemed-to-Satisfy Provisions. This is because a ceiling that has resistance to the incipient spread of fire is tested in the horizontal plane.

If roof lights are installed in a building, it may be necessary to install part of the ceiling in the vertical plane to connect the roof light with the ceiling below. Where this occurs, it may be necessary for a building proponent to provide evidence to an appropriate authority that the method proposed will meet the requirements of Clause 3.6(c).

However, in this case, if the material is installed on a vertical plane yet complies in all other respects with the tested prototype, it is unlikely that the ceiling's fire performance will be affected.

In the storey immediately below the roof, under circumstances specified in Clause 3. 7, it is permissible to reduce or (in some cases) delete the FRL of:

• columns, other than those in that are:
  • within 1.5 metres of a window;
  • face that window; and
  • exposed to a fire-source feature through that window; and
• internal walls, other than fire walls and shaft walls.

Clause 3.7 does not negate the need for internal columns to have the same FRL as an external column (set out in Clause 3.1 ( f)) where that internal column is:

• within 1.5 metres of a window;
• faces that window; and
• exposed to a fire-source feature through that window.

The Clause 3.8 concession is based on the BCA’s overall assumption that there is generally a lower risk to the occupants of open spectator stands and indoor sports stadiums than in other buildings. The reasons for this concession are that:

• an open spectator stand generally has a low fire load, even though it may have a high population, particularly during an event, and is open at the front, facilitating the ventilation of smoke and heat; and
• in most indoor sports stadiums large areas are usually inaccessible to the public (being taken up as part of the sporting events) and the finishes are generally spartan.

See Schedule 3 for definition of “open spectator stand”.

Clause 3.9 and Table 3.9 are based on experimental research carried out at the BHP Research Laboratories. The research included full-scale fire tests on open-deck and enclosed carparks, and was supplemented by extensive overseas testing.

The research showed that the Table 3.9 FRLs will not lead to an unsafe situation or structural failure of a building element in an open-deck carpark, or an enclosed carpark, which is sprinkler protected.

See Schedule 3 for definition of “carpark”. Clause 3.9(b) refines this definition when the expression is used in Clause 3.9 and Table 3.9.

Clause 3.9 concessions include:

• a building which solely comprises a carpark (see Clause 3.9(a)(i));
• the carpark section of a building which, in part, has another use, and where the carpark and that use are fire-separated as required in Clause 3.9(a)(ii)(A)-(D) (regardless of the classification of that use, or whether that use is next to, above or below the carpark) (see Clause 3.9(a)(ii));
• any administrative area associated with the carpark, such as ticket selling and fee collection areas (see Clause 3.9(b)(i)(A)); and
• in a sprinkler protected carpark, small areas ancillary to a Class 2 or Class 3 building, such as part of the carpark used for normal ‘household’ storage (see Clause 3.9(b)(i)(B)).

Clause 3.9 concessions exclude:

• any area of another Class (see Clause 3.9(b)(ii)(A));
• another Class 7 use (i.e. other than carparking), (see Clause 3.9(b)(ii)(A)); and
• an area “specifically intended” for the parking of vehicles such as trucks, buses, vans and the like (see Clause 3.9(b)(ii)(B)).

Clause 3.9 and Table 3.9, while using a refined definition of “carpark”, also use the undefined expression “carparking”. This word specifically refers to the parking of cars. This is also the intention of refining the definition of “carpark” as expressed by the use of the words “specifically intended” in Clause 3.9(b)(ii)(B).

The purpose of refining this definition, which is to limit the concessions in Table 3.9 to areas used for the parking of lighter vehicles (that is, vehicles other than commercial trucks, vans, buses and the like), rather than simply limiting them to areas used for the parking of cars only.

Accordingly, it would seem contrary to the purpose of this clause to exclude from the refined definition and the word “carparking” such vehicles as motor bikes, van-like family vehicles, non-commercial panel vans, and smaller non-commercial utilities.

Table 3.9 permits building elements to have either a specified FRL or a specified surface area to mass ratio. In relation to columns and beams, Table 3.9 does not require them to have an FRL if they have the specified surface area to mass ratio. Some authorities refer to this ratio as the “heat sink effect”, in that the lower the exposed surface area to mass ratio, the lower will be the member temperature for a given fire.

The concession of Table 3.9(a) relating to columns, only applies to columns of any material which support a roof which is not used for carparking, and located 3 metres or more from a fire-source feature to which they are exposed.

The concession of Table 3.9(b) only applies to steel columns which support a roof which is used for carparking, and/or located less than 3 metres from a fire-source feature to which they are exposed. This concession is not applicable if the steel columns support any other part of the building which is not used as a carpark.

Columns of any material that do not qualify for Table 3.9(a) and 3.9(b) concessions are subject to Table 3.9(c).

In the section of Table 3.9 relating to roofs, there is a concession for roofs that are not used for carparking.

A roof used for carparking must comply with any relevant requirements of Table 3.9 (eg those relating to floor slabs).

Clause 3.10 results from research undertaken by the National Association of Forest Industries and Forest and Wood Products Australia, which have been confirmed by overseas studies.

Clause 3.10 provides a concession to Clause 3.1(d) and also to the combustibility requirements of C1.9(a) and (b) and C2.6 to allow, subject to specified conditions, the use in certain Class 2 and 3 buildings, timber framing instead of an alternative structural support system using non-combustible materials, concrete, or masonry.

In addition to timber framing, Clause 3.10(a)(ii) allows the use of non-combustible materials (such as steel) for fire walls and internal walls required to be fire resisting, instead of concrete or masonry as required by Clause 3.1(d).

For the purposes of this concession “framing” includes bracing components. However, a cladding element (despite providing nominal bracing) cannot be considered “framing” for the purposes of this concession.

Clause 3.10(b) allows the top three storeys of a four storey Class 2 or 3 building to be constructed with timber framing and/or non-combustible materials if they are located above a single storey used for vehicle parking (note that the limitation in Clause 3.9 by use of the word “carparking” does not apply here) and ancillary purposes. These ancillary purposes include such items as individual storerooms, laundries, and the like.

To achieve this concession, the lowest carparking storey (including the floor/ceiling between the carpark and the storey above) must be constructed of concrete or masonry, and have the FRLs specified in Table 3, or reduced by Clause 3.10(c). The floor between the carpark and the storey above must not contain penetrations or openings that would reduce the fire-resisting performance of the floor. The exception to this is a door which is permitted to be a –/60/30 self-closing fire door.

Under the Clause 2.8 concession, the vehicle parking storey can be classified as a Class 2 or 3 building for the purpose of determining the relevant fire-resisting requirements of Specification C1.1 .

The basis of the Clause 3.10(b) concession is that the concrete or masonry floor of the first storey above the lowest carparking storey will provide adequate fire separation. Clause 3.10 does not require smoke detectors or sprinklers in the lowest carparking storey because a fire occurring in it should not pose an unacceptable risk to occupants evacuating from the upper three storeys.

Compliance must still be achieved with the other requirements of Specification C1.1 and other parts of the BCA, including the relevant FRLs listed in Table 3 of Specification C1. 1, and any relevant requirements of Clause E1.5.

Subject to the conditions listed, including the installation of a sprinkler system, Clause 3.10(c) allows:

• a reduction of the FRL of loadbearing walls (see Clause 3.10(c)(i)); and
• the deletion of the FRL for non-loadbearing internal walls (see Clause 3.10(c)(ii)).

Reference to Clause 2 of Specification E1.5 indicates one of the technical standards that the sprinkler system may comply with is AS 2118.4—Automatic fire sprinkler systems—Residential. This Standard has been specifically developed to provide a degree of life safety and property protection for occupants of low-rise Class 2 and 3 buildings. If the storey used as carpark requires sprinklers by Clause E1.5, then the carpark is considered a Class 7 building for the purposes of applying Specification E1.5 (see E1.5).

Clause 3.10(c)(ii) allows non-loadbearing internal walls to have no FRL. The concession is subject to the requirement that the internal walls be lined on each side with 13 mm standard grade plasterboard or non-combustible materials with a similar fire-resisting performance. This means that all doors from sole-occupancy units to corridors, when applying these concessions, must be smoke proof doors. Self-closing solid core doors satisfy this requirement (see Specification C3.4 ).

The Clause 3.10(c)(ii)(B) provision regarding the height of a non-loadbearing wall, to which this concession is applied, aims to create a smoke proof wall, hence the requirement for sealing any cracks and openings against the spread of smoke.

The Clause 3.10(c)(ii)(C) requirement that only non-combustible insulation can be used in a cavity in a non-loadbearing wall, to which this concession is applied, aims to limit the spread of fire by way of the cavity.

Table 4 of Specification C1.1 sets out the required FRLs of building elements in a building required to be of Type B construction. The required FRL depends on whether the element is loadbearing or non-loadbearing, if the element comprises or is incorporated in an external wall, and its distance from any fire-source feature to which it is exposed.

Although a roof is an external building element that can be exposed to a fire-source feature, it is not required to comply with the FRLs specified under the heading of external wall in Table 4. The FRLs required for a roof are contained under the heading of roofs near the bottom of the Table.

When using Table 4 of Specification C1.1 , it should be noted that Clause 6 of Schedule 5 permits the deletion of the structural adequacy criterion of an FRL for non-loadbearing elements. The reason for this is that if such an element fails during a fire, there will be no flow-on collapse of other elements. See Schedule 3 for the definition of “loadbearing”.

Generally speaking, Type B construction differs from Type A construction by allowing lower FRLs for external walls, generally not requiring roofs and floors to have an FRL, and not requiring FRLs for ventilation, garbage, and similar shafts.

These differences are based on the lower rise in storeys allowed by Table C1.1 ; and the smaller size of Type B construction buildings allowed by Table C2.2 .

The BCA requires the floors of buildings required to be of Type B construction to have an FRL in Class 2 and Class 3 buildings, if the floor supports different sole-occupancy units (see Clause 4.1(i)), in Class 9a buildings as part of the fire compartments required by C2.5(a)(iv) and in Class 9c buildings as part of the fire compartments required by C2.5(b)(ii) (see Clause 4.1(j)).

Clause 4.1(a) requires building elements to achieve at least the FRLs set out for them in Table 4. Clause 4.1(a) only applies to the building elements listed in Table 4, and any beams or columns incorporated in such building elements.

Clause 4.1(c) requires stair shafts which support floors or structural parts of floors to either have a specified FRL, or be constructed at the junction of the shaft and floor (or part of floor), so that if the floor falls or collapses (fully or partly) during a fire, the shaft will not be damaged.

Clause 4.1(d) requires internal walls to extend to a barrier to stop or limit the spread of fire over the top of the wall. Such a requirement is not considered necessary when a sole-occupancy unit occupies the whole of the top storey. This concession applies to buildings of Type B construction. Clause 4.1(d) only applies to internal walls required to have an FRL with respect to integrity and insulation. This is consistent with the intent that the walls are only required to extend to the underside of a floor or roof, etc when the wall is required to perform a fire separating function.

Clause 4.1(e) requires loadbearing internal walls and loadbearing fire walls (in both cases, including those which are part of a loadbearing shaft) to be of concrete, masonry or constructed from fire-protected timber (however, fire-protected timber has certain limitations).

Under Clause 4.1(g), internal columns and internal walls need not comply with Table 4 if they are:

• in a Class 5–9 building;
• in the storey immediately below the roof; and
• not fire walls or shaft walls.

Clause 4.1(i) does not apply if the storeys being separated are within a sole-occupancy unit of a Class 2 or 3 building, because it is likely that the two levels are connected by a non-fire-isolated stairway.

The primary reason for the Clause 4.1(i) fire separation requirement is that in a building fire, the highest degree of risk is attached to such people as the very young, people with disabilities, the elderly, and those who are asleep.

Table 5 requires internal walls bounding a stair required to be rated to have an FRL of 60/60/60. The reason for this is because although Table C1.1 only allows buildings of Type C construction to have a maximum rise is storeys of 2, such buildings may include a basement which is not included in the calculation of rise in storeys. If a stairway in the building connects say a basement with two other storeys, in accordance with D1.3, a fire-isolated exit would be required. Table 5 then sets out the required FRL for the walls of the stairway.

Clause 4.2 and Table 4.2 are based on experimental research carried out at the BHP Research Laboratories. The research included full scale fire tests on both open-deck and enclosed carparks, and was supplemented by extensive overseas testing.

The research carried out on this matter showed that the Table 4.2 FRLs will not lead to an unsafe situation or structural failure of a building element in an open-deck carpark, or an enclosed carpark which is sprinkler protected.

See Schedule 3 for definition of “carpark”. Clause 4.2(b) refines this definition when the expression is used in Clause 4.2 and Table 4.2.

Clause 4.2 concessions include:

• a building which solely comprises a carpark;
• the carpark section of a building which elsewhere has another use;
• any administrative area associated with the carpark, such as ticket selling and fee collection areas; and
• in a sprinkler protected carpark, small areas ancillary to a Class 2 or Class 3 building, such as part of the carpark used for normal “household” storage.

Clause 4.2 concessions exclude:

• any area of another Class;
• another Class 7 use (i.e. other than carparking); and
• an area “specifically intended” for the parking of vehicles such as trucks, buses, vans and the like.

Clause 4.2 and Table 4.2, while using a refined definition of “carpark”, also use the undefined expression “carparking”. This word specifically refers to the parking of cars. This is also the intention of refining the definition of “carpark” as expressed by the use of the words “specifically intended” in Clause 4.2(b)(ii)(B).

However, in applying these provisions, it is important to consider the purpose of refining this definition, which is to limit the concessions in Table 4.2 to areas used for the parking of lighter vehicles (that is, vehicles other than commercial trucks, vans, buses and the like)—rather than simply limiting them to areas used for the parking of cars only.

Accordingly, it would seem contrary to the purpose of this clause to exclude from the refined definition and the word “carparking” such vehicles as motor bikes, van-like family vehicles, non-commercial panel vans, and smaller non-commercial utilities.

Regarding certain types of column and beam, Table 4.2 permits them to have either a specified FRL or a specified surface area to mass ratio. In other words, in relation to these columns and beams, Table 4.2 does not require them to have an FRL if they have the specified surface area to mass ratio. Some authorities refer to this ratio as the “heat sink effect”, in that the lower the exposed surface area to mass ratio, the lower will be the member temperature for a given fire.

The concession for columns in Table 4.2(a) applies to columns of any material which support a roof which is not used for carparking, and located 3 metres or more from a fire-source feature to which they are exposed.

The concession in Table 4.2(b) only applies to steel columns that support a roof which is used for carparking, and/or located less than 3 metres from a fire-source feature to which they are exposed. This concession is also applicable where steel columns support any other part of the building that is not used as a carpark.

Columns of any material which do not qualify for the Table 4.2(a) and (b) concessions are subject to Table 4.2(c).

For the purposes of this clause, the usual definition of “carpark” is specifically amended (see Clause 4.2(b)).

Table 3.9 provisions restricting the roof concession to those roofs that are not used for carparking does not apply to Table 4.2.

The differences between Table 4.2 and Table 3.9 are based on the lower rise in storeys allowed for Type B construction buildings by Table C1.1 .

Clause 4.3 results from research undertaken by the National Association of Forest Industries and Forest and Wood Products Australia, which have been confirmed by overseas studies.

Clause 4.3 provides a concession to Clause 4.1(e) and also to the combustibility requirements of C1.9(a) and (b) to allow, subject to specified conditions, the use in certain Class 2 and 3 buildings, timber framing instead of an alternative structural support system using non-combustible materials, or concrete, or masonry.

In addition to timber framing, Clause 4.3(a)(ii) allows the use of non-combustible materials (such as steel) for fire walls and internal walls required to be fire-resisting, instead of concrete or masonry as required by Clause 4.1(e).

For the purposes of this concession “framing” includes bracing components. However, a cladding element (despite providing nominal bracing) cannot be considered “framing” for the purposes of this concession.

Table C1.1 limits Class 2 and 3 buildings of Type B construction to a rise in storeys of two. For this reason Clause 4.3 only applies to two storey Class 2 and 3 buildings, and no concession is allowed for a two storey timber framed building above a concrete or masonry lower storey, as is allowed in the case of Type A construction buildings by Clause 3.10.

Clause 4.3(b) allows a 2 storey Class 2 or 3 building to be constructed with timber framing and/or non-combustible materials if the lowest storey is used for vehicle parking (note that the limitation in Clause 4.2 by use of the word “carparking” does not apply here) and ancillary purposes. These ancillary purposes include such items as individual storerooms, laundries, and the like.

To achieve this concession, the lowest carparking storey (including the floor/ceiling between the carpark and the storey above) must be constructed of concrete or masonry, and have the FRLs specified in Table 4. The floor between the carpark and the storey above must not contain penetrations or openings that would reduce the fire-resisting performance of the floor. The exception to this is a doorway which is permitted to be protected by a –/60/30 self-closing fire door.

Under the Clause 2.8 concession, the carparking storey can be classified as a Class 2 or 3 building for the purpose of determining the relevant fire-resisting requirements of Specification C1.1 .

Subject to the conditions listed, including the installation of a sprinkler system, Clause 4.3(c) allows a reduction of the FRL of loadbearing elements, and the deletion of the FRL for non-loadbearing elements.

Reference to Clause 2 of Specification E1.5indicates one of the technical standards that the sprinkler system may comply with is AS 2118.4—Automatic fire sprinkler systems—Residential. This Standard has been specifically developed to provide a degree of life safety and property protection for occupants of low-rise Class 2 or 3 buildings (see E1.5).

Clause 4.3(c)(ii)(A) allows non-loadbearing internal walls to not have an FRL. The concession is subject to the requirement that the internal walls be lined on each side with 13 mm standard grade plasterboard or non-combustible materials.

The Clause 4.3(c)(ii)(B) provision regarding the height of a non-loadbearing wall to which this concession is applied aims to create a smoke proof wall, hence the Clause 4.3(c)(ii)(D) requirement for sealing any cracks and openings against the spread of smoke.

The Clause 4.3(c)(ii)(C) requirement that only non-combustible insulation can be used in a cavity in a non-loadbearing wall to which this concession is applied aims to limit the spread of fire by way of the cavity.

There is no specific concession to permit the use of solid core doors in Type B construction buildings, unlike that in Clause 3.10(c)(ii)(E), this is because they are already permitted in Type B construction (see C3.11).

The result of Clause 4.3 is that a designer proposing to use the BCA Deemed-to-Satisfy Provisions to design a two storey Class 2 or 3 building of Type B construction has three basic options:

• design in accordance with other provisions applicable to buildings of Type B construction which, under C1.9(a) and (b) and Clause 4.1(e) would exclude the use of timber external walls, common walls, loadbearing internal walls, fire walls and non-loadbearing internal walls required to be fire-resisting;
• use timber and/or non-combustible materials in accordance with Clause 4.3; or
• comply with C1.5 and design for Type C construction, which places no limitations on the use of timber.

Table 5 of Specification C1.1 set out the required FRLs of building elements in a building required to be of Type C construction. If the element comprises or is incorporated in an external wall, the required FRL depends on distance from any fire-source feature to which it is exposed.

Although a roof is an external building element that can be exposed to a fire-source feature, it is not required to comply with the FRLs specified under the heading of external wall in Table 5. The FRLs required for a roof are contained under the heading of roofs near the bottom of the table.

When using Table 5 of Specification C1.1, it should be noted that Clause 6 of Schedule 5 permits the deletion of the structural adequacy criteria of an FRL for non-loadbearing elements. The reason for this is that if such an element fails during a fire, there will be no flow-on collapse of other elements. See Schedule 3 for definition of “loadbearing”.

Generally speaking, Type C construction differs from Type B construction by allowing lower FRLs for external walls which are located more than 1.5 metres from a fire-source feature, and only requiring a maximum FRL of 90 minutes for any criterion. Table C2.2 bases these differences on the lower rise in storeys allowed by Table C1.1, and the smaller size of Type C buildings allowed.

No building element in a building required to be of Type C construction is required to be non-combustible, or of concrete or masonry.

Clause 5.1(a) requires building elements to achieve at least the FRLs set out for them in Table 5. Clause 5.1(a) only applies to the building elements listed in Table 5, and any beams or columns incorporated in such building elements.

Where Table 5 requires an external wall to have an FRL, Clause 5.1(b) requires that the wall only need be tested from outside to meet the FRL criteria. This allows the use of brick veneer construction where the brick has the required FRL.

Where a fire wall and the specified internal walls are of lightweight construction they must comply with Specification C1.8.

Clause 5.1(d) requires internal walls to extend to a barrier to stop or limit the spread of fire over the top of the wall.

The concession contained in Clause 4.1(d) for Type B construction with respect to the height of the wall when a sole-occupancy unit occupies the whole of the top storey, does not apply to Type C construction.

To protect building occupants of Class 2, 3 and 9 buildings from fire spread between storeys, Clause 5.1(e) establishes the minimum fire separation between storeys in such buildings. This requirement takes into account the special risks that can exist in such buildings.

This requirement also relates to the fire separation of Class 2, 3 and 9 buildings from a carpark or storage area.

Clause 5.1(e) does not apply if the storeys being separated are within a sole-occupancy unit of a Class 2 or Class 3 building, because it is likely that the two levels are connected by a non-fire-isolated stairway and would therefore not be required to be fire separated.

The primary reason for the Clause 5.1(e) and (f) fire separation requirement is that in a building fire, the highest degree of risk is attached to such people as the very young, people with disabilities, the elderly, and those who are asleep.

Clause 5.2 and Table 5.2 are based on experimental research carried out at the BHP Research Laboratories. The research included full scale fire tests on both open-deck and enclosed carparks, and was supplemented by extensive overseas testing.

The research carried out on this matter showed that the Table 5.2 FRLs will not lead to an unsafe situation or structural failure of a building element in an open-deck carpark, or an enclosed carpark which is sprinkler protected.

See Schedule 3 for definition of “carpark”. Clause 5.2(b) refines this definition when the expression is used in Clause 5.2 and Table 5.2.

The Clause 5.2 concessions include:

• a building which solely comprises a carpark;
• the carpark section of a building which elsewhere has another use;
• any administrative area associated with the carpark, such as ticket selling and fee collection areas; and
• in a sprinkler protected carpark, small areas ancillary to a Class 2 or Class 3 building, such as part of the carpark used for normal ‘household’ storage.

The Clause 5.2 concessions exclude:

• any area of another Class;
• another Class 7 use (i.e. other than carparking); and
• an area “specifically intended” for the parking of vehicles such as trucks, buses, vans and the like.

Clause 5.2 and Table 5.2, while using the refined definition of “carpark”, also use the undefined expression “carparking”. This word specifically refers to the parking of cars. This is also the intention of refining the definition of “carpark” as expressed by the use of the words “specifically intended” in Clause 5.2(b)(ii)(B).

However, in applying these provisions, it is important to consider the purpose of refining this definition, which is to limit the concessions in Table 5.2 to areas used for the parking of lighter vehicles (that is, vehicles other than commercial trucks, vans, buses and the like), rather than simply limiting them to areas used for the parking of cars only.

Accordingly, it would seem contrary to the purpose of this clause to exclude, from the refined definition and the word “carparking”, such vehicles as motor bikes, van-like family vehicles, non-commercial panel vans, and smaller non-commercial utilities.

Regarding certain types of columns and beams, Table 5.2 permits them to have either a specified FRL or a specified surface area to mass ratio. In other words, in relation to these columns and beams, Table 5.2 does not require them to have an FRL if they have the specified surface area to mass ratio. Some authorities refer to this ratio as the “heat sink effect”, in that the lower the exposed surface area to mass ratio, the lower will be the member temperature for a given fire.

In the section of Table 5.2 relating to columns:

• the concession of (a) applies only to steel columns that are located less than 1.5 metres from any fire-source feature; and
• the concession of (b) applies only to columns of any material which are located less than 1.5 metres from any fire-source feature.

Columns of any material that do not qualify for the (a) and (b) concessions are subject to (c).

Roofs that do not qualify for the roof concession in Table 5.2 must comply with the requirements of Specification C1.1 for roofs of other buildings.

Table 3.9 provisions restricting the roof concession to those roofs that are not used for carparking does not apply to Table 5.2.

The differences between Table 5.2 and Table 4.2 are based on the lower rise in storeys allowed for Type C buildings by Table C1.1.