Class 1a buildings are typically detached residential houses and also include attached townhouses, row-houses and villas. A Class 1a dwelling cannot be located above another dwelling or class of building.
Fire safety in a building can be improved by either
- Preventing the spread of fire from a dwelling of origin to other attached or nearby dwellings.
The purpose of this objective is to minimise the potential fire size, as well as limiting the fire to the dwelling of origin only.
To achieve this objective elements of construction are required to achieve a certain fire resistance level and a critical aspect of construction is to ensure that construction joints and penetrations for services are adequately sealed.
- Using materials that are less likely to burn, to minimise the likelihood of fire spreading as well as the generating smoke and toxic gases. This objective is achieved by ensuring certain materials satisfy required early fire hazard indices, or are non-combustible, particularly in shared/common areas associated with attached class 1a buildings.
Building requirements
To minimise the spread of fire, fire growth as well as safety of occupants in the event of a fire a building must be constructed so as to satisfy the requirements of:
- Part 3.7 of the Building Code of Australia - Housing Provisions (Volume 2)
- AS4072.1 and AS1530.4 with regard to fire stopping service penetrations.
- Manufacturer’s Specification to ensure that the product performs as tested.
Alternative Solutions
If any of the above requirements cannot be met, either because of innovative development, or there is a particular construction issue, the building would not comply with the Deemed-to Satisfy Requirements of the Building Code of Australia and consequently a Construction Certificate, or an Occupation Certificate will not be able to be issued.
To overcome this situation the an Alternative Solution may be able to be prepared in accordance with Clause 1.0.8, 1.0.9, & 1.0.10 of the BCA Housing Provisions, demonstrating that the method of construction will satisfy the Performance Requirements under BCA Housing Provisions - Part 2.3:
- Providing evidence that the form of construction satisfies the BCA Housing Provisions;
- Using a Verification Method;
- Comparison with the Deemed-to-Satisfy provisions
- Expert judgement
General Deemed-to-satisfy Requirements
To satisfy the Deemed-to-Satisfy provisions of the BCA Housing Provisions with respect to insulation or sarking, the designer must ascertain:
- If the insulation is required as part of a building element system requiring a fire resistance level (FRL) such as a separating wall
- Whether the product is combustible
- The products early fire hazard properties;
- Which product to use in which specific situation
It is critical to understand that no single product can be used in all situations. Each product has its own performance characteristics in a fire situation. Part 1.2 of the BCA Housing Provisions provides the methodology for determining the suitability of a particular material or form of construction. The BCA Housing Provisions refers to Specification A2.3 of the BCA (Volume 1), which sets out the procedures for determining the FRL of building elements and Specification A2.4 of the BCA, which sets out the procedures for establishing a material’s fire hazard properties.
Therefore to demonstrate that a product such as insulation or sarking is suitable to be used in a building it would have to have been tested by a registered testing authority and have some form of certification or accreditation, otherwise the installer will not be able to demonstrate that the product satisfies the requirements of the BCA.
Consequently the designer must familiarise themselves with the manufacture’s specification to ensure that the product will perform as it was tested to ensure that the work will satisfy the requirements of the BCA.
Deemed-to-satisfy Requirements Fire Separation
Part 3.7 of the BCA requires that dwellings either be setback an appropriate distance from the property boundary or from another building to minimise the risk of fire spread between dwellings. Typically, the external walls are required to be setback at least 900mm from an allotment boundary or 1800mm from another dwelling on the same allotment.
Should a detached dwelling be located closer than 900mm from an allotment boundary, the external wall must achieve a fire resistance level (FRL) of no less than 60/60/60 tested from the outside and extend from the footings to the underside of a non-combustible roof covering or non-combustible eave lining. This only applies to the wall facing the boundary, any perpendicular wall that is 90 degrees or greater to the boundary is not considered exposed and does not require fire rating. Eaves must not encroach closer than 450mm, and fascia boards, gutters and downpipes must be non-combustible if within 450mm of the boundary.
Additionally, should a Class 10a building such as a garage be located between a Class 1 building and the allotment boundary or another building on the same allotment, it must be ensured that the Class 10 building does not facilitate fire spread to the Class 1 building. This does not apply to a boundary with a public road or space. Fire separation is achieved by either:
- Ensuring the adjacent Class10 building is setback at least 900mm from the boundary or 1800mm from another building, or
- Ensuring the adjacent Class 10 building is setback at least 900mm from the Class 1 building, or
- Separating the Class 10 building from the boundary or other building by a fire rated external wall (FRL of 60/60/60), or
See Figures 3.7.1.4 for a full illustrated list of scenarios.
Should a dwelling be directly attached to another dwelling, such as a townhouse or duplex, the dwellings must be separated by a fire resisting separating wall that achieves a fire resistance level of no less than 60/60/60. Such a wall must extend from the footing to the underside of a non-combustible roof covering, or extend 450mm past any combustible roof lining.
Eaves, verandahs and the like that are common to more than one Class 1a dwelling must have a non-combustible vertical lining to prevent fire spread via this building area.
There are numerous diagrams contained within Part 3.7 of the BCA Housing Provisions that illustrate the above fire separation requirements.
Deemed to Satisfy Requirement for Sealing Penetrations
As separating walls between Class 1a buildings are required to be fire rated to 60/60/60, it is important that any openings in this wall do not allow the spread of fire.
Designers often require openings through a separating wall for services such as plumbing or sometimes mechanical services. To prevent the spread of fire via the services, these penetrations must be capable of maintaining an FRL of with respect to integrity and insulation (ie -/60/60) under BCA Housing Provisions Clause 3.7.1.8(f).
Electrical wires or cables penetrating a separating wall must also be protected to prevent the spread of fire by achieving an FRL of no less than -/60/60, or:
- The service must be installed so that the opening is neatly formed, cut or drilled and no closer than 50mm to another service;
- The opening is for a singe cable no larger in cross section than 2000mm2, with the ‘fire stopped’ gap being no wider tan 15mm, or
- 500m2 I any other case;
- The fire-stopping material (such as high-temperature mineral or ceramic fibre) must be packed into the gap between the service and wall, floor or ceiling in a manner, and compressed to the same degree, as adopted for testing.
For an electrical switch, socket, outlet or the like is accommodated in a recess in a hollow wall or hollow floor/ ceiling system the cavity immediately behind the service must be framed and packed with fire-stopping material.
Deemed to Satisfy Requirement for Fire Stopping Wall & Roof Junctions
To avoid the spread of fire between attached dwelling over a separating wall
the BCA Housing Provisions Clause 3.7.1.8 (c) & (d) requires that the wall extend to the underside of the non-combustible roof lining. In such a situation there will be a construction joint creating a gap between the top of the wall and the underside of the roof. This gap must be sealed to prevent the spread of fire by using a material such as mineral fibre that maintains its integrity as well as insulation properties in a fire scenario.
Any gap between a separating wall and a masonry veneer external wall must also be protected so that fire can not spread via this gap. Such gaps must be no larger than 50mm and packed with mineral fibre or similar. It must also be ensured that the packing is arranged so as to maintain the required weatherproofing requirements of the BCA.
To ensure that the product used to seal these gaps is appropriate, it must have been tested and either a certificate of accreditation or a certificate of conformity. The appropriate authority can allow any complying tested service penetration without the need to refer to a test report, provided it is satisfied that “an adequate level of performance is maintained”.
A number of proprietary products are suitable for sealing construction joints, if they have been previously tested in accordance with AS 1530.4 to demonstrate they have achieved the required fire-resistance level (FRL).
Deemed-to-satisfy Requirements Early Fire Hazard Properties
It is important that the spread of fire and the development of smoke be limited during a fire until building occupants have had time to evacuate. Compared to Class 2-9 buildings, Class 1a buildings do not have as stringent restrictions on building materials fire hazard properties and do not contain any requirements for floor, wall and ceiling linings such as carpets and timber wall panelling. However the following building elements must comply in Class 1a buildings:
- Sarking type materials used in the roof must have a flammability index of not greater than 5, this requirement also extends to any common roof space with an adjacent Class 10 building such as a garage.
- Flexible ductwork used for the transfer of products initiating from a heat source that contains a flame must comply with the fire hazard properties set out in AS4254, such as Clause 2.7 which in general states that insulation used for ducts liners must have a smoke developed index of not greater than 3 and spread of Flame index of 0 (refer to standard for complete details)
There are no other restrictions for Fire Hazard Properties in a Class 1a building.
Learn more
Definitions
Certificate of Accreditation
A Certificate of Accreditation is issued by a State or Territory accreditation authority and is evidence that a building material, method of construction or design (subject to any specified conditions or limitations) is accepted within that State or Territory as complying with the BCA. Certificates of Accreditation are no longer issued by the ABCB. Certificates issued by the ABCB under the previous scheme are no longer valid.
Certificate of Conformity
A Certificate of Conformity issued under the ABCB scheme is evidence that a building material, method of construction or design (subject to any specified conditions or limitations) is accepted within all States and Territories as complying with the BCA.
Combustible
A test done in accordance with AS 1530.1 will determine if a material is combustible. If materials used in an assembly contain combustible components, then the assembly is combustible.
Fire-resisting
Applies to fire-resisting building elements, including structural members and non-loadbearing components, such as cladding, doors, windows and the like.
Flammability Index
A test performed in accordance with AS 1530.2 will determine the flammability index of a material.
Habitable room means a room used for normal domestic activities, and—
(a) Includes a bedroom, living room, lounge room, music room, television room, kitchen, dining room, sewing room, study, playroom, family room and sunroom; but
(b) Excludes a bathroom, laundry, water closet, pantry, walk-in wardrobe, corridor, hallway, lobby, photographic darkroom, clothes-drying room, and other spaces of a specialised nature occupied neither frequently nor for extended periods
Insulation
Insulation is the third criterion used when specifying an FRL.
Integrity
Integrity is the second criterion used when specifying an FRL. See example under “insulation” definition.
The test under AS 1530.4 considers that a building element has failed the integrity criterion when either the element collapses, or the element develops cracks, fissures or other openings through which flames or hot gases can pass.
Non Combustible
Clause C1.12 of the BCA lists materials deemed to be non-combustible. These materials may be used wherever a material is required to be non-combustible. In some instances the material may contain combustible components. The materials listed are not intended to apply to fire place hearths.
The following materials, though combustible or containing combustible fibres, may be used wherever a non-combustible material is required:
- Plasterboard.
- Perforated gypsum lath with a normal paper finish.
- Fibrous-plaster sheet.
- Fibre-reinforced cement sheeting.
- Pre-finished metal sheeting having a combustible surface finish not exceeding 1 mm thickness and where the Spread-of-Flame Index of the product is not greater than 0.
- Bonded laminated materials where—
- Each laminate is non-combustible; and
- Each adhesive layer does not exceed 1 mm in thickness; and
- The total thickness of the adhesive layers does not exceed 2 mm; and
- The Spread-of-Flame Index and the Smoke-Developed Index of the laminated material as a whole does not exceed 0 and 3 respectively.
-
Spread-of-Flame Index
A test in accordance with AS/NZS 1530.3 determines the Spread-of-Flame Index of a material. The index is based on a logarithmic scale of 0 to 10. A lower index number indicates better performance.
Standard Fire Test
AS 1530.4 contains details of the Standard Fire Test. The test is used to determine the FRL of a building element. The results are recorded in order as: structural adequacy, integrity and insulation.
Structural Adequacy
In relation to an FRL, means the ability to maintain stability and adequate loadbearing capacity as determined by AS1530.4.
Verification Method means a test, inspection, calculation or other method that determines whether a Building Solution complies with the relevant Performance Requirements.