NCC 2022 Volume Two - Building Code of Australia Class 1 and 10 buildings

H3

Part H3 Fire safety

Part H3 Fire safety

Introduction to this Part

This Part is intended to minimise the risk of illness, injury or loss of life occurring due to fire. It includes requirements to avoid the spread of fire between buildings (including garage-top dwellings), smoke alarms and evacuation lighting in Class 1b buildings.

Objectives

The Objective is to—

  1. safeguard the occupants from illness or injury by alerting them of a fire in the building so that they may safely evacuate; and
  2. avoid the spread of fire.

Functional Statements

A Class 1 building is to be protected from the spread of fire.

A Class 1 building is to be provided with safeguards so that occupants are warned of a fire in the building so that they may safely evacuate.

Performance Requirements

(1) A Class 1 building must be protected from the spread of fire such that the probability of a building not being able to withstand the design heat flux of 92.6 kW/m² for a period of 60 minutes shall not exceed 0.01, when located within 900 mm from the allotment boundary or within 1.8 m from another building on the same allotment from—

  1. another building other than an associated Class 10 building; and
  2. the allotment boundary, other than a boundary adjoining a road or public space (see Figure H3P1).

SA H3P1 Spread of fire2019: P2.3.1

Delete subclause H3P1(1) and insert H3P1(1) as follows:

(1) A Class 1 building must be protected from the spread of fire from—

  1. another building other than an associated Class 10 building; and
  2. the allotment boundary, other than a boundary adjoining a road or public space; and
  3. a Class 10b brush fence.

(2) A Class 10a building must not significantly increase the risk of fire spread between Class 2 to 9 buildings.

Figure H3P1 Typical areas of potential fire spread
image-H3P1-typical-areas-of-potential-fire-spread.svg
Figure Notes

This diagram indicates areas of potential fire spread. This situation will differ for corner allotments, etc.

In a Class 1 building, occupants must be provided with automatic warning on the detection of smoke with an efficacy greater than 0.95 and a reliability greater than 0.95, so that they may evacuate in the event of a fire to a place of safety appropriate to the—

  1. function and use of the building; and
  2. occupant characteristics; and
  3. fire load and combustion characteristics; and
  4. potential fire intensity; and
  5. fire hazard.

Verification Methods

Compliance with H3P1(1)(a) to avoid the spread of fire between buildings on the same allotment is verified when—

  1. the external walls and any openings in the external walls of a building, less than 1.8 m from another building, are capable of withstanding 92.6 kW/m2 of heat flux for 60 minutes; and
  2. the external walls extend to the underside of a non-combustible roof covering or non-combustible eaves lining in accordance with clause 9.2.3 of the ABCB Housing Provisions.

Compliance with H3P1(1)(b) to avoid the spread of fire from an allotment boundary is verified when—

  1. the external walls and any openings in the external walls of a building, less than 0.9 m from an allotment boundary, are capable of withstanding 92.6 kW/m2 of heat flux for 60 minutes; and
  2. the external walls extend to the underside of a non-combustible roof covering or non-combustible eaves lining in accordance with clause 9.2.3 of the ABCB Housing Provisions.

Compliance with H3P1(2) to avoid the spread of fire between buildings on adjoining allotments is verified when it is calculated that—

  1. a building will not cause heat flux in excess of those set out in column 2 of Table H3V3 at locations within the boundaries of an adjoining property set out in column 1 of Table H3V3 where another building may be constructed; and
  2. when located at the distances from the allotment boundary set out in column 1 of Table H3V3, a building is capable of withstanding the heat flux set out in column 2 of Table H3V3 without ignition.

Explanatory information

H3V3 is equivalent to C1V1 in NCC Volume One. Guidance on the use of C1V1 can be found in the Guide to NCC Volume One, and is applicable to the use of H3V3.

Table H3V3 Heat flux (adjoining allotment)
Column 1 (Location) Column 2 (Heat flux [kW/m2])
On boundary 80
1 m from boundary 40
3 m from boundary 20
6 m from boundary 10

Compliance with H3P1(2) to avoid a Class 10a building increasing the risk of fire spread between Class 2-9 buildings is verified when it is calculated that a building—

  1. is capable of withstanding the heat flux set out in column 2 of Table H3V4 without ignition; and
  2. will not cause heat flux in excess of those set out in column 2 of Table H3V4, when the distance between the buildings is as set out in column 1 of Table H3V4.

Explanatory information

H3V4 is equivalent to C1V2 in NCC Volume One. Guidance on the use of C1V2 can be found in the Guide to NCC Volume One, and is applicable to the use of H3V4.

Table H3V4 Heat flux (same allotment)
Column 1 (Location) Column 2 (Heat flux [kW/m2])
0 m 80
2 m 40
6 m 20
12 m 10

Deemed-to-Satisfy Provisions

(1) Where a Deemed-to-Satisfy Solution is proposed, Performance Requirements H3P1 and H3P2 are satisfied by complying with H3D2 to H3D6.

(2) Where a Performance Solution is proposed, the relevant Performance Requirements must be determined in accordance with A2G2(3) and A2G4(3) as applicable.

(1) The following materials, though combustible or containing combustible fibres, may be used wherever a non-combustible material is required:

  1. Plasterboard.
  2. Perforated gypsum lath with a normal paper finish.
  3. Fibrous-plaster sheet.
  4. Fibre-reinforced cement sheeting.
  5. Pre-finished metal sheeting having a combustible surface finish not exceeding 1 mm thick and where the Spread-of-Flame Index of the product is not more than 0.
  6. Sarking-type materials that do not exceed 1 mm in thickness and have a Flammability Index not greater than 5.
  7. Bonded laminated materials where—
    1. each lamina, including any core, is non-combustible; and
    2. each adhesive layer does not exceed 1 mm in thickness and the total thickness of the adhesive layers does not exceed 2 mm; and
    3. the Spread-of-Flame Index and the Smoke-Developed Index of the bonded laminated material as a whole do not exceed 0 and 3 respectively.

(2) The fire hazard properties of materials used in a Class 1 building, including floor or ceiling spaces common with a Class 10 building, must comply with the following:

  1. Sarking-type materials used in the roof must have a Flammability Index not greater than 5.
  2. 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 AS 4254.1.

Compliance with Part 9.2 of the ABCB Housing Provisions satisfies Performance Requirement H3P1 for fire separation of external walls.

Compliance with Part 9.3 of the ABCB Housing Provisions satisfies Performance Requirement H3P1 for fire protection of separating walls and floors.

NCC Blurbs

Compliance with NSW Part 9.4 of the ABCB Housing Provisions satisfies Performance Requirement H3P1 for fire separation of garage top dwellings.

NCC Title

Fire separation of garage top dwellings

NCC State
NSW
NCC Variation Type
Replacement
NCC SPTC Current
Fire separation of garage top dwellings

Compliance with Part 9.4 of the ABCB Housing Provisions satisfies Performance Requirement H3P1 for fire separation of garage-top dwellings.

(1) Compliance with Part 9.5 of the ABCB Housing Provisions satisfies Performance Requirement H3P2 for smoke alarms and evacuation lighting.

(2) For the purposes of (1), a Class 1 building includes a Class 10a private garage located above or below the Class 1 building.

Explanatory information: Smoke alarms general requirements

Performance RequirementH3P2 and the Deemed-to-Satisfy Provisions of Part 9.5 of the ABCB Housing Provisions require automatic warning on the detection of smoke in buildings, so that occupants may be alerted to a fire in order to evacuate to a place of safety.

Explanatory information: Different smoke alarm requirements for Class 1a and Class 1b buildings

Part 9.5 of the ABCB Housing Provisions specifies different smoke alarm requirements for Class 1a and Class 1b buildings. The main difference is that a Class 1b building is required to have a greater number of smoke alarms, i.e. smoke alarms must be installed in all bedrooms, and a system of lighting must be installed to assist evacuation. This is due to Class 1b buildings generally being used for more transient purposes and the occupants being less familiar with the building layout.

Explanatory information: Smoke alarms complying with AS 3786

Clause 9.5.1(b) of the ABCB Housing Provisions requires a smoke alarm(s) to comply with AS 3786. AS 3786 contains the requirements for the design and performance of electrically operated smoke alarms containing both detection and alarm facilities. Types of smoke alarms prescribed in AS 3786 include photoelectric, ionisation or a combination of the two.

Explanatory information: Smoke alarms to be connected to consumer mains source

Clause 9.5.1(c) of the ABCB Housing Provisions requires that a smoke alarm be connected to the consumer mains electricity source where a consumer mains source is supplied to the building. A smoke alarm complying with AS 3786, that is intended for connection to an external power source, is required to be provided with a secondary power source i.e. a source of power to supply the smoke alarm in the event that the primary power source is unavailable. Generally, the requirement is met by providing mains powered smoke alarms with a battery back-up.

Explanatory information: Interconnection of smoke alarms

Clause 9.5.1(d) of the ABCB Housing Provisions requires that alarms be interconnected to provide a common alarm so that if one alarm in the dwelling activates, the other alarms automatically activate, which will increase the likelihood of sleeping occupants becoming aware of the detection of smoke. Alarms of a Class 1 building need not be interconnected with alarms in another Class 1 building or a private garage which does not belong to the Class 1 building.

Explanatory information: Location of smoke alarms

When deciding on the position of smoke alarms it is important to remember that they are intended to detect smoke before it reaches the sleeping occupants of a building.

The ensuing alarm is designed to wake the occupants and give them time to evacuate the building.

Explanatory information: Smoke alarms required on other storeys not containing bedrooms

In addition to a smoke alarm being required to be provided on storeys containing bedrooms, a smoke alarm is also required on each other storey that is not already provided with a smoke alarm even if those storeys consist of only carparking, bathrooms, laundries and the like. “Storey” in this context differs from the definition contained in the NCC which excludes such spaces from being considered as storeys.

Reference to “storey” only applies within a single dwelling. For example, if a storey contains a private garage belonging to the Class 1a dwelling in addition to a private garage which does not belong to the Class 1a dwelling, smoke alarms must be installed in both private garages.

Where the other storey is a Class 10a private garage, clause 9.5.1(b) of the ABCB Housing Provisions permits the use of any other alarm deemed suitable in accordance with AS 1670.1 provided smoke alarms complying with AS 3786 are installed elsewhere in the Class 1 building.

Explanatory information: Nuisance alarms

Smoke alarms are extremely sensitive and may detect smoke and moisture created by common household activities such as burnt toast or steam from a bathroom.

Accordingly, to reduce the likelihood of nuisance alarms, it is preferable that smoke alarms are not located near cooking appliances and bathrooms. However, if it is necessary to locate alarms in these positions, the type of alarm installed may need to be considered as some alarm types may be more suitable in certain locations.

Explanatory information: Added flexibility when considering smoke alarm location

The options described in the ABCB Housing Provisions are not the only means available for complying with this Part. The performance-based nature of the NCC provides flexibility to develop alternative methods if it is preferred to meet the Performance Requirement in some other way. This added flexibility may be utilised when considering the location of smoke alarms.