NCC 2019 Volume One
Part G4 Construction in alpine areas (DtS)

Part G4 Construction in alpine areas (DtS)

Deemed-to-Satisfy Provisions

G4.0 Deemed-to-Satisfy Provisions


Where a Deemed-to-Satisfy Solution is proposed, Performance Requirements GP4.1 to GP4.4 are satisfied by complying with—


for a building containing an occupiable outdoor area, Part G6.


Where a Performance Solution is proposed, the relevant Performance Requirements must be determined in accordance with A2.2(3) and A2.4(3) as applicable.


The requirements of GP4.1GP4.4 will be satisfied if compliance is achieved with G4.1G4.9in the case of buildings in alpine areas and for occupiable outdoor areas, Part G6.

G4.1 Application of Part


The Deemed-to-Satisfy Provisions of this Part apply to any building constructed in an alpine area in addition to other Deemed-to-Satisfy Provisions of the BCA.


Where any Deemed-to-Satisfy Provisions are in conflict, the provisions of this Part take precedence.


To clarify that Part G4 applies only to buildings in alpine areas, and its provisions override any others in the BCA which are in conflict.

Buildings in alpine areas only—G4.1(a)

G4.1(a) indicates that the requirements of Part G4 only apply to buildings constructed in an alpine area. See the definition of Alpine area in Schedule 3.

Precedence over other provisions—G4.1(b)

G4.1(b) indicates that the provisions of Part G4 take precedence over any other provisions in the BCA, but only if they are in conflict.

G4.2 *  *  *  *  *

Explanatory information

This clause has deliberately been left blank.

This provision was blank in BCA 1990. G4.2 has been left blank rather than renumber subsequent clauses.

G4.3 External doors

External doors which may be subject to the build-up of snow must—


open inwards or slide; and


If inward opening, be marked "OPEN INWARDS" on the inside face of the door in letters not less than 75 mm high in a colour contrasting with that of the background; and


be constructed so that the threshold is not less than 900 mm above the adjoining surface; and


if it serves a corridor or stairway, be positioned in an alcove or recess with—


no horizontal dimensions of the alcove or recess less than twice the width of the door; and


the door positioned to open against a wall such that the distance from any part of its swing to the nearest point of entry of the stairway or corridor is not less than the width of the door.


To enable people to evacuate a building in an alpine area in an emergency without being impeded by snow and ice.

Inwards opening external doors
Doors in non-alpine areas

In most buildings, exit doors must open outwards to assist with evacuation. The outward opening door swings in the direction of people leaving the building. A door opening towards people leaving is considered to be potentially more dangerous because a “crush” may occur, where people pushing against the door prevents it from being opened.

Doors in alpine areasG4.3(a) and (b)

In alpine conditions, the swing of outward opening doors may be impeded by snow and ice outside. Therefore, the door is allowed to open inwards provided adequate precautions are taken to enable the door to open towards the flow of people.

As external doors in most buildings open outwards, most people will not necessarily be expecting a door to open inwards. Accordingly, a readily-visible and understood sign must alert people to this feature.

Doorways protected by alcoves or similar

Doorways protected from snow build-up by alcoves, etc are effectively exempt from G4.3, so long as they are clearly not subject to the build up of snow.


Where a doorway serves a corridor or stairway, an alcove or recess must be provided to protect against snow build-up. If a design indicates that such an alcove or recess will prevent snow build up, a builder, etc may be able to adopt the approach referenced above, and avoid the necessity for the door to open inwards. See Figure G4.3.

G4.3(d) does not apply where an external doorway opens directly from a room to the outside of the building.

Figure G4.3 Minimum dimensions of alcove or recess at external doorway
Thresholds to required exit doorwaysG4.3(c)

Every threshold to a required exit doorway must be located so that snow, etc will not prevent the door from opening. Accordingly, the threshold may need to be:

  • elevated to a point where it is above anticipated snow levels in that area of the building; or
  • protected by an awning or similar enclosure which prevents snow from obstructing the doorway.

Attention should be given to the geometry of the building where the threshold is located. The doorway should not be in a place where the roof will deposit large amounts of snow, or at re-entrant corners where snow drifts may form.

G4.4 Emergency lighting

In a Class 2, 3, 5, 6, 7, 8 or 9 building or Class 4 part of a building, a system of emergency lighting must be installed in accordance with the Deemed-to-Satisfy Provisions of Part E4


in every stairway (other than those within a sole-occupancy unit in a Class 2 or 3 building or Class 4 part of a building); and


in every public corridor or the like leading to an exit; and


externally above every doorway opening to a road or open space; and


in any storey of the building if illumination sufficient for safe egress will not be available under conditions of emergency.


To enable people to evacuate a building in an alpine area in an emergency without being impeded by lack of light.

Emergency lighting in buildings in alpine areas

G4.4 requires emergency lighting in all Class 2–9 buildings in alpine areas. Expected delays in emergency personnel arriving on the scene, means emergency lighting is necessary to assist people evacuating.

Emergency lighting provides illumination for exit paths, etc during a power failure (which is a likely scenario in a fire). The lighting must be effective and installed to cover exit paths as nominated.

G4.4 and Part E4

The technical aspects of the installation of emergency lighting must be in accordance with Part E4. However, the location of emergency lights must comply with G4.4, irrespective of any location parameters specified in Part E4.

Lighting in stairways—G4.4(a)

G4.4(a) requires lighting to be provided to every stairway within a building, except within a sole-occupancy unit of a Class 2 or 3 building and the Class 4 part of a building. This is to make sure that common exit routes are still negotiable in an emergency.

Lighting in exit paths—G4.4(b)

G4.4(b) requires lighting in main exit paths. The key description is public corridors, public hallways or the like, inferring that any pathway used as a general or common exit route by occupants must be provided with emergency lighting.

Emergency lighting—G4.4(c)

G4.4(c) requires emergency lighting externally above every doorway opening to a road or open space. This enables occupants to negotiate any obstacles when evacuating in darkness.

G4.4(c) applies only to doorways leading directly or via the allotment land to a public road. Doorways opening on to enclosed courtyards or similar enclosed areas are not required to comply.

Emergency lighting and darkness—G4.4(d)

G4.4(d) is a performance criterion, and will require assessment of the building layout to determine the need for emergency lighting in areas other than those specified in G4.4(a), (b) and (c). The aim of G4.4 is to assist people by providing illumination in paths of travel while evacuating the building.

Where the designer or appropriate authority believes there are problems which may be created due to darkness, then emergency lighting must be installed.

Exit signs— Part E4

Note that while it is not referenced in Part G4, emergency exit signs need to be installed in accordance with Part E4.

G4.5 External trafficable structures

External stairways, ramps, access bridges or other trafficable structures serving the building must—


have a floor surface that consists of expanded mesh if it is used as a means of egress; and


have any required barrier designed so that its sides are not less than 75% open; and


for a stairway have, goings (G), risers (R) and slope relationship quantity (2R + G) in accordance with—


Table G4.5; and


for a ramp serving as an exit and not serving as an accessible ramp, have a gradient not steeper than 1:12; and


where a ramp is also serving as an accessible ramp under Part D3, be in accordance with AS 1428.1.

Table G4.5 Alternate stair riser and going dimensions (mm)

Riser (R)

Going (G)

Slope relationship

(2R + G)














To enable people to evacuate a building in an alpine area in an emergency without being impeded by steep ramps.

External ramps must not be too steep

G4.5 aims to ensure that egress is not impeded by steep ramps. The maximum slope of 1:12 is less than the 1:8 allowed in Part D2 because of the difficulty associated with negotiating ramps in snow and ice conditions. G4.5(a) acknowledges that if exit ramps are required for access by people with disabilities they must comply with AS 1428.1.

G4.6 Clear space around buildings

A building must be so constructed that—


if any part of an external wall is more than 3.6 m above the natural ground level — the distance of that part from a boundary other than a road alignment is not less than 2.5 m plus an additional 100 mm for each 300 mm or part by which that part of the wall exceeds a height of 3.6 m; and


if an exit doorway discharges into a court between wings of a building and that area may be used for vehicle access to the building, the distance between wings must be not less than 4 m; and


where an exit doorway discharges opposite a feature that could entrap snow or an embankment that is more than 900 mm above the threshold of the doorway, a distance of not less than 4 m must be provided between the doorway and the feature.


To enable people to evacuate and emergency services to access a building in an alpine area in an emergency without being impeded by snow build-up around the building.

Snow build-up between and around buildings

The design and construction of a building in an alpine area must not aid dangerous levels of snow build-up between and around buildings. This control:

  • assists with egress in an emergency;
  • helps vehicle access around the buildings, both for snow clearing and emergency situations; and
  • minimises the risk of snow or ice falling from the roof on to adjoining lots or egress routes.

G4.6(a) addresses the set-back distance for external walls from the boundary of adjoining allotments. The aim is to make sure that a reasonable distance is created between buildings to reduce the amount of snow build-up between properties. G4.6(a) applies only to the area adjacent to that part of the wall which is more than 3.6 metres in height.

G4.6(b) describes distances between wings of a building where the exit doorway discharges into this area. The external walls of a building should not create an alcove which traps snow, making evacuation difficult.

G4.6(c) deals with the problem of features adjacent to an exit doorway which could trap snow and complicate egress.

The term “barrier” is used to describe the feature which could entrap snow. Because the aim of G4.6(c) is to avoid the problems created by snow drifts, it would be reasonable to interpret “barrier” as including any feature which could hold the snow, including fences, cuttings to roadways, walls of adjacent buildings and the like. See Figure G4.6.

Figure G4.6 Discharge of External Doorways in alpine areas

G4.7 * * * * *

Explanatory information

This clause has deliberately been left blank.


To enable people to evacuate and emergency services to access a building in an alpine area in an emergency without being impeded by inadequate structures comprising part of the exit path of travel to a safe place.

Slipperiness and safe barriers

G4.7 aims to make sure that external structures comprising part of the exit path of travel from a building to a safe place:

  • have a floor surface preventing people from slipping; and
  • have any required barrier (i.e. required by Part D2) designed so that it is more than 75 per cent open to minimise snow build-up.

This provision only applies to structures, and not to such paths of travel as steps and ramps created by landscaping.

G4.8 Fire-fighting services and equipment


Every Class 2, 3, 5, 6, 7, 8 or 9 building must have—


a manually operated fire alarm system with call-points complying with AS 1670.1; and


fire hydrants installed in accordance with E1.3(b); and


fire hose reels installed in accordance with E1.4(b) to (g), except that—


in a Class 2 or 3 building—


for the purpose of E1.4(b), a sole-occupancy unit is considered to be a fire compartment; and


for the purpose of E1.4(c)(ii), a sole-occupancy unit may be served by a single fire hose reel located at the level of egress from that sole-occupancy unit; and


for the purpose of E1.4(f), a fire hose may pass through a doorway in bounding construction referred to in C3.11.


The requirements of (a)(iii) do not apply to a Class 8 electricity network substation.


To provide for the installation of adequate fire safety equipment suitable to the conditions experienced in alpine areas.

Fire alarm system—G4.8(a)(i)

G4.8(a)(i) requires a manually-operated, fire-alarm system. This system must be supplemented by call-points to notify the local fire authority. The activation mechanism of the manual call-point may also activate the alarm system. This will provide an additional audible warning to the automatic systems required by E2.2.

Where an external alarm is installed, sub-zero temperatures must not freeze its mechanism.


G4.8(a)(ii) requires that hydrants be installed in all the nominated buildings in accordance with E1.3(b). A fire hydrant must be operable in sub-zero conditions, and any water in the mains should not freeze.

Hose reels—G4.8(a)(iii)

G4.8(a)(iii) requires that hose reels be installed in all the nominated buildings in accordance with E1.4, except that E1.4(b), E1.4(c)(ii) and E1.4(f) are modified for Class 2 and 3 buildings.

  • G4.8(a)(iii)(A)(aa)—Fire hose reels are required to be installed, irrespective of whether fire hydrants are required, if fire compartments exceed 500 m2. For the purpose of a Class 2 or 3 building, a sole-occupancy unit is considered a fire compartment.
  • G4.8(a)(iii)(A)(bb)—Generally, fire hose reels are required to be installed on the storey they are to service. In the case of Class 2 or 3 buildings, a concession is provided when a sole-occupancy unit occupies more than one storey if the fire hose reel is located at the level egress from that sole-occupancy unit. There is no limitation on the size or number of storeys within the sole-occupancy unit served by the hose.
  • G4.8(a)(iii)(A)(cc)—Doors to sole-occupancy units of Class 2 or 3 buildings may remain open for the hose to pass through. To require a fire hose reel in each sole-occupancy unit could be impractical, therefore fire hose reels are allowed to be placed in a common area and then pass through the entrance door to the unit.

A fire hose reel must be operable in sub-zero conditions, and any water in the mains should not freeze.

Class 4 parts of buildings

G4.8 has not been applied to Class 4 parts of a building. It is extremely unlikely that any of the services and equipment required by G4.8 will be located within a sole-occupancy unit in any residential building. In, for example, Class 2 and Class 3 buildings it is most likely that such services and equipment will be located in common areas.

The requirement for the installation of fire-fighting services and equipment in the non-Class 4 parts of the building within which the Class 4 part is located, will provide for the safety of the occupants of the Class 4 part.

Electricity network substations

G4.8(b) provides an exemption to the requirements for fire hose reels for electricity network substations.

G4.9 Fire orders

Every Class 2, 3 or 9 building must display a notice clearly marked “FIRE ORDERS” in suitable locations near the main entrance and on each storey, explaining—


the method of operation of the fire alarm system and the location of all call-points; and


the location and methods of operation of all fire-fighting equipment; and


the location of all exits; and


the procedure for evacuation of the building.


To enable occupants to evacuate a building in an alpine area in an emergency without being impeded by lack of knowledge of the fire safety system, egress routes or evacuation procedures.


In Class 2, Class 3 and Class 9 buildings, G4.9 requires that a notice containing fire orders be displayed. They are necessary because there is a high probability that, in alpine areas, the occupants may be residing overnight or for short periods only, and will be unfamiliar with their surroundings.

Fire escape information needs to be displayed prominently near the main entrance and on each storey so that people new to the building can identify escape features, etc. A suitable location would be near the primary stairway. Additional advice on locating these items can be obtained from the appropriate authority or local fire authority.

Information must be conveyed in a clear and simple manner, because of the varying degree of technical understanding of people reading this information.

Class 4 parts of buildings

Class 4 parts of buildings have not been included in the coverage of G4.9 because buildings will not typically be used for short term rental accommodation in alpine areas. Therefore, residents are likely to be aware of safety requirements.