Specification C1.1 Fire-Resisting Construction

Exposure to fire-source features

Refer to the definition in 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.

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.

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 ).

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 ).

illustrates the alternatives for an external loadbearing wall of a Class 5 building required to be of Type A construction.

2.2

Fire protection for a support of another part

Intent

To minimise the risk that a building element required to have a fire-resistance level (FRL) will fail during a fire due to the failure of another element required to give it vertical or lateral support.

Support of building elements with an FRL

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, 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.

Exceptions of building elements

lists a number of exemptions to and .

The lateral support for the types of wall referred to in is considered unnecessary in these cases, because allows the use of brick veneer walls, and 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 , and 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.

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

exempts certain columns, as listed in , from having an FRL.

Under 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

2.3

Lintels

Intent

To minimise the risk that the failure of a lintel over an opening in a wall required to have a fire-resistance level (FRL) will result in the failure of the wall during a fire.

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.

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

and 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.

2.4

Attachments not to impair fire-resistance

Intent

To minimise the risk that a finish, lining or attachment to a wall or roof required to have a fire-resistance level (FRL) will:

• impair the FRL of the wall or roof to which it is attached;
• compromise the safe evacuation of the building; and
• lead to the spread of fire by way of the building facade.

does not prohibit the use of combustible materials as a finish, lining or other attachment to a wall, roof or other building element required to have an FRL.

However, the combustible material can only be used if the material:

• is one of the exemptions from fire hazard properties listed in , or complies with the fire hazard properties prescribed in (see );
• is not located in a position to make a required exit unusable in a fire, therefore it will not compromise the building's safe evacuation (see );
• will not lead to the spread of fire by way of the building facade (see ); and
• will not impair the FRL of the wall, roof or other building element to which it is attached (see ).

only applies to the use of finishes or linings, and other attachments. prohibits a required FRL of a building part from being reduced by the attachment of facings or finishes or the installation of ducting or any other service.

2.5

General concessions

Intent

To permit the use of certain building practices known to provide acceptable levels of fire safety.

The concessions contained in 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 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 are not likely to lead to the spread of fire, especially as they are required to be non-combustible. The intent of 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 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 . 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 , or . 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.

2.6

Mezzanine floors: Concession

Intent

To provide concessions for small mezzanines.

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

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

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 .

2.7

Enclosure of shafts

Intent

To minimise compromising the fire-resisting performance of a shaft.

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.

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

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 ), or the bottom of the shaft is laid on the ground (see ).

2.8

Carparks in Class 2 and 3 buildings

Intent

To allow the use of residential levels of fire protection to be used for carparks in certain Class 2 and Class 3 buildings.

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 .

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 and );
• in the case of Class 2 buildings, contain no more than 4 storeys (see ); 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 ).

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 .

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

2.9

Residential aged care building: Concession

Intent

To allow concessions for the fire protection of certain building elements in Residential aged care buildings when a suitable sprinkler system is used to achieve an adequate level of occupant safety.

“Residential aged care building” is defined in .

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 ) meant that those concessions could not be used for many aged care hostels. The concessions in 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 applies to the requirements for floors and loadbearing walls as set out in Table 3, or . of . 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 . The conditions outlined in 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 ); 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 ).

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 , and walls must still comply with the requirements of —Sound Transmission and Insulation.

Other provisions relating to Residential aged 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.

Fire-resistance of building elements

requires building elements to achieve at least the FRLs set out in .

only applies to the building elements listed in , and any beams or columns incorporated in such building elements.

requires the floor and floor framing of lift pits to be non-combustible because of the fire risks caused by the tendency for combustible material to accumulate in these places.

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

Under Clause 3.1(e)(i), any non-loadbearing internal wall that is required to be fire-resisting must be of non-combustible material.

Under Clause 3.1(e)(ii), any non-loadbearing shaft that is not used for discharging such combustion products as smoke, coals or embers must be of non-combustible construction.

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

Fire-resistance of building elements

Carparks

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 A1.1 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.

Class 2 and 3 buildings: Concession

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.

The effect of Clause 4.3 is to provide a concession to Clause 4.1 to allow, subject to specified conditions, the use in certain Class 2 and 3 buildings of timber framing instead of an alternative structural support system using non-combustible materials, or concrete, or masonry.

Clause 4.3(a)(i) allows the use of 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).

Clause 4.3(a)(iii) allows a combination of timber framing and non-combustible materials.

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.

The Clause 4.3(a) concession to use timber framing and/or non-combustible materials is conditional on:

• a fire wall or internal wall required to be fire-resisting being extended to the underside of the non-combustible roof covering. The wall height requirement, together with the smoke sealing requirement of Clause 4.3(c)(ii)(D), aims to create a smoke proof wall, hence the requirement for sealing any cracks and openings against the spread of smoke;
• only non-combustible insulation being used in a wall cavity. This aims to limit the spread of fire by way of the cavity; and
• an automatic smoke alarm system being installed in the building to give early warning of a fire.

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 that the required sprinkler system need only comply with 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 Clause 4.1(b), (e) and (f), 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.

Fire-resistance of building elements

sets 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 . The FRLs required for a roof are contained under the heading of roofs near the bottom of the table.

When using , it should be noted that 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 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. bases these differences on the lower rise in storeys allowed by , 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.

requires building elements to achieve at least the FRLs set out for them in . only applies to the building elements listed in , and any beams or columns incorporated in such building elements.

Where requires an external wall to have an FRL, 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 .

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 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, 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.

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 and 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.

Carparks

and 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 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 for definition of “carpark”. refines this definition when the expression is used in and .

The 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 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.

and , 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 .

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, 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 must comply with the requirements of for roofs of other buildings.

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

The differences between and are based on the lower rise in storeys allowed for Type C buildings by .