Part D2 Construction of exits

See Deemed-to-Satisfy Provisions of D1.0.

Except as outlined below, Part D2 does not apply within sole-occupancy units in Class 2 or Class 3 buildings or Class 4 parts. The path from within the units to the door opening from them is not regarded as a path of travel to an exit. For these buildings, the path of travel to an exit commences at the outside of the door to the sole-occupancy unit. The path inside the unit, leading to the door, is part of the “evacuation route” (see the definition of this term in Schedule 3).

D2.13 deals with the construction of stair treads and risers. For the safety of people moving within a sole-occupancy unit, it is important that stair treads and risers are safe to use.

D2.14(a) requires the installation of landings in stairways. For the safety of people moving within a sole-occupancy unit, it is important that landings be provided. This also links with D2.13(a) to limit the maximum number of risers in a flight of stairs to 18.

D2.16 deals with barriers. Appropriate barriers are required to minimise the risk of people falling from a landing, balcony, roof with public access, flight of stairs and the like.

D2.18 allows steeper stairs to infrequently used areas of a building. This concession applies to infrequently used areas such as machinery rooms, boiler rooms, etc and attics and storerooms in sole-occupancy units in Class 2 buildings and Class 4 parts. Under D2.18, the designer has the choice of designing the stair, landing, barrier and handrail to comply with the appropriate provisions of the NCC or with AS 1657.

D2.2 sets the criteria for the materials and methods of construction used in stairways and ramps within a fire-resisting shaft.

D2.2(a) and (b) set out the requirements for maintaining the integrity of the fire protection to the shaft of a fire-isolated stairway and ramp. These provisions reflect the fact that:

• occupants who use the stairway or ramp during a fire will expect to remain reasonably safe while evacuating, relying on the protection provided by the fire-isolated stairways and ramps to safely evacuate the building; and
• the stairway or ramp provides protection to the fire brigade to undertake search and rescue, and fire-fighting operations.

Where the installation of non-fire-isolated stairways and ramps is required by the NCC, they must provide a safe means of egress.

Such stairways and ramps will not be within a fire-resisting shaft, but they are nonetheless expected to be structurally sound, and constructed of materials which will not readily support combustion.

D2.3 requires that required non-fire-isolated stairways and ramps must be either constructed in accordance with D2.2 or the alternative options set out in D2.3(a)–(c).

D2.3(c)(ii) permits the use of glued timber members under certain conditions. The aim of these conditions is to minimise the risk represented by certain types of glue which delaminate during a fire.

A danger exists that, in an emergency, a person may mistakenly pass the lowest floor providing direct egress to a road or open space. D2.4(a) minimises the risk of this by requiring that there is no direct connection between the rising and descending flight of a stairway at the level from which egress is obtained.

If, in order to achieve D2.4(a), rising and descending flights of stairs are separated by construction (which may in places be common to the two flights), that construction must comply with the smoke separation requirements contained in Clause 2 of Specification C2.5.

Figure D2.4 illustrates one method of compliance with D2.4.

Figure D2.4 Plan showing one method of compliance with D2.4

Table E2.2a allows the use of an open access ramp or balcony instead of stairwell pressurisation. If this option is chosen then D2.5 aims to prevent the entry of smoke into a fire-isolated exit by allowing smoke to vent naturally through an open access ramp or balcony, before it reaches the fire-isolated exit.

D2.5(a) sets out the requirements for ventilation openings where an open access ramp or balcony forms part of a required exit. This helps the evacuation of occupants using the exit by enabling the natural ventilation of smoke.

The reason for permitting an enclosure up to a height of one metre under D2.5(b) is to allow for a solid barrier or balcony.

Note that the opening above one metre cannot be enclosed for more than 25 percent of the area of its sides. This allows for adequate smoke ventilation, while permitting some limited enclosure.

Figure D2.5 illustrates three methods of compliance with D2.5, and one method that does not comply.

Figure D2.5 Plan showing compliance and non-compliance with D2.5

D2.6 only applies to a smoke lobby required by D1.7.

A smoke lobby required by D1.7 must be constructed in accordance with each of the requirements in D2.6(a)–(d).

The intumescent putty referred to in D2.6(b)(iii) is intended to expand when exposed to fire, thus sealing any opening at the top of the lobby against smoke. If another material is proposed, it must be no less effective than the putty.

Paths of travel within a building must continue to provide safe evacuation during an emergency. To achieve this, D2.7 restricts the installation of certain services in fire-isolated exits, non-fire-isolated exits, and certain paths of travel to exits.

D2.7 should be read in conjunction with C3.9, which lists the services that may penetrate fire-isolated exits.

D2.7(a) prohibits access to services (apart from fire-fighting and detection equipment) from within a fire-isolated exit because they are a potential source of smoke or fire. Doors to service enclosures, if left open, could also hamper evacuation. The prohibition also means that maintenance equipment will not be placed within the enclosure.

D2.7(b) prohibits any chute or duct carrying products of combustion from a boiler, incinerator fireplace or the like from being installed in:

• any required exit (i.e. both fire-isolated exits and non-fire-isolated exits); and
• any corridor, hallway, lobby or the like leading to a required exit (i.e. it does not apply to other paths of travel to an exit).

An opening from a chute or duct that forms part of a smoke hazard management system is permitted.

D2.7(c) prohibits the installation of any gas or other fuel service in a required exit (i.e. both fire-isolated exits and non-fire-isolated exits). This prohibition does not apply to a path of travel to an exit.

Under specified conditions, D2.7(d) allows certain electrical and communication services to be located in:

• D2.7(d)(iv)—any required non-fire-isolated exit (installation in required fire-isolated exits is effectively prohibited by the reference to D2.7(a)); and
• D2.7(d)(v)—any corridor, hallway, lobby or the like leading to a required exit (i.e. it does not apply to other paths of travel to an exit).

D2.7(e) allows electrical wiring to be installed within a fire-isolated exit if the wiring is associated with specified equipment and systems serving the exit or systems used for alarms and monitoring of fire safety systems.

Spaces under stairways are often used for a range of purposes. It is common practice to have a cleaner’s store located in such spaces. These stores often contain flammable cleaning agents.

If the stairway or ramp is fire-isolated, and the space below is part of the fire-isolated shaft, that space must not be used as a cupboard or the like.

If the stairway or ramp is fire-isolated, and the space below is not part of the fire-isolated shaft, that space may be used as a cupboard etc. This could be created by placing a fire rated slab under the flight of stairs. This is shown in Figure D2.8.

If the stairway or ramp is non-fire-isolated, any cupboard underneath must be fire separated from the stairway. The construction must have an FRL of 60/60/60, with a self-closing –/60/30 fire door.

Figure D2.8 Section showing enclosure of space below fire-isolated stairway

Most people using stairways tend to move in easy reach of a handrail or barrier. This tendency is particularly pronounced during an emergency evacuation. The D2.9 maximum of two metres (effectively permitting a reach of one metre to either side) is considered reasonable.

Wider stairways are permitted, with more than two metres between the handrails. However, for the purposes of calculating required widths, such stairways are deemed to add no more than two metres to the aggregate required width.

Under D2.10(a), a fire-isolated ramp may be used instead of a fire-isolated stairway if:

• the construction enclosing the ramp complies with the requirements of the NCC for fire-isolated stairways; and
• the width and ceiling height of the ramp complies with the requirements of the NCC for fire-isolated stairways.

D2.10(b) specifies safe gradients for a ramp used as a required exit. They are determined having regard to likely users.

Ramps for people with a disability, as specified by Part D3, require a gradient of not less than 1:14, and in other cases, not less than 1:8.

D2.10(b) relates to a ramp being used as a fire-isolated exit. If the ramp is also used for access it must comply with the requirements for such ramps in Part D3.

Under D2.10(c), the floor surface of a ramp must be slip resistant to avoid people slipping over and injuring themselves. The surface must have a slip-resistance classification when tested in accordance with AS 4586. There are a number of parameters to be considered: two ramp slopes, two tests (the wet pendulum test or the oil-wet inclining platform test) and there are two conditions (dry or wet).

To determine the appropriate slip-resistance classification surface to apply to a ramp, it is necessary to determine the conditions (either dry, wet or both) that the relevant surface is likely to be subjected over the life of the building.

A dry surface is one that is not normally wet or not likely to become wet other than by accidental spill.

A wet surface is one that is normally wet or likely to be made wet other than by an accidental spill. This could include a surface that is exposed to weather such as an external ramp, and a surface that may, on occasions, become wet such as a surface in a transitional space like an entrance airlock or entrance lobby.

Other potentially wet affected areas such as bathrooms are not included in the NCC provisions unless they a have a ramp incorporated in them.

Surfaces affected by commercial or industrial processes are regulated by the relevant workplace safety authority.

Under D2.11(a), the required FRL of a fire-isolated passageway must (except as set out in D2.11(b)):

• D2.11(a)(i)—not fall below the required FRL of any fire-isolated stairway or ramp which discharges into the passageway; and
• D2.11(a)(ii)—in every other case, not fall below 60/60/60.

The FRL test is for a fire outside the passageway, in another part of the building. It is extremely unlikely that a fire will occur inside a fire-isolated passageway.

Despite the requirements of D2.11(a), D2.11(b) allows the top of a fire-isolated passageway to be constructed without an FRL on the condition that its walls are built up to either of the following:

The top construction of a fire-isolated passageway need not have an FRL if the walls continue to the underside of a non-combustible roof covering.

Under D2.11(b)(ii), a fire-isolated passageway need not have a top construction with an FRL, and need not have its walls extend to the underside of a non-combustible roof covering if the walls extend to the underside of a ceiling which is resistant to the incipient spread of fire for at least 60 minutes.

Figure D2.11 Elevations showing alternative methods of protecting a fire-isolated passageway from a fire in another part of the building

Such a ceiling will prevent the ignition of combustible materials in the roof or ceiling space from a fire below. For the ceiling to be effective, the whole fire compartment surrounding the passageway must also be covered. This will minimise the risk of a fire spreading into the fire compartment’s roof or ceiling space, and entering the passageway from above. An incipient spread of fire resistant ceiling is not required over the passageway, because it is extremely unlikely that a fire will start there.

It is important that the junction between the top of the wall and the incipient spread of fire resistant ceiling is adequately sealed to maintain the integrity of the barrier.

Figure D2.11 illustrates this comment.

Exits must provide egress to a road or an open space. D2.12 applies where the open space is provided by a roof. To maximise the safety of people who must use a roof as the point of discharge from an exit, such a roof is required:

• D2.12(a)—to have an FRL sufficient to protect people on the roof from fire below during evacuation from the building; and
• D2.12(b)—not to have any openings within three metres of the path of travel to the portion of the roof being used as open space, and from that portion to a road. This protects a person passing such openings from being affected by a fire on the other side of such openings.

Once on the roof, a safe path of travel must be provided to a road. See D1.10.

The going and riser requirements in D2.13 date from a substantial reform carried out in 1987, based on international research.

D2.13(a)(i) states that a stairway must have no more than 18 nor less than 2 risers in each flight. Where there are less than 2 risers in a flight, they do not comprise a stairway for the purposes of the NCC.

Eighteen risers is considered to be the maximum reasonable number that an average person can negotiate before requiring a rest.

Winders are counted as part of the maximum number of 18 risers. More than one riser is considered necessary for a person to observe and adjust to a change in level.

The purpose of D2.13(a)(ii) and (iii) and (b)(ii) and (iii) is to achieve constant going and riser dimensions deemed safe for people to walk up and down. This minimises the risk of people overstepping during descent on uneven stairs (due to short goings) and tripping on ascent (due to high risers). Table D2.13 expresses ratios between goings and risers which are considered safe for use.

D2.13(a)(iii) and (b)(ii) accounts for conditions such as movement of materials due to atmospheric moisture changes or minor deviations related to variations in materials which affect finished stair dimensions.

Figure D2.13(1) illustrates adjacent risers within a flight with minor deviations in the materials affecting the finished stair dimensions. The nominated riser height is exceeded by riser A. As a consequence riser height B is less than the nominated riser height. The difference between riser A and riser B cannot exceed 5 mm.

Figure D2.13(2) illustrates an entire flight with minor deviations in the materials affecting the finished riser dimensions. In addition to the 5 mm difference permitted between adjacent goings or risers, the maximum difference between the smallest and largest going or riser within a flight must not exceed 10 mm.

Despite the deviations shown in both Figure D2.13(1) and Figure D2.13(2), the stairs in the flight are deemed constant.

Irrespective of any minor deviations permitted by D2.13(a)(iii) and (b)(ii), finished going and riser dimensions must not exceed the limitations stipulated in Table D2.13.

Figure D2.13(1) Deviations in adjacent risers

Notes:

1. A = larger riser of two adjacent risers.
2. B = smaller riser of two adjacent risers.
3. This figure only shows deviations in risers, however the same principle can apply for goings.

Figure D2.13(2) Deviations over a flight

Notes:

1. C = largest riser of the flight.
2. D = smallest riser of the flight.
3. This diagram only shows deviations in risers, however the same principle can apply for goings.

D2.13(a)(iv) allows the use of open stair risers. However, it limits the opening to 125 mm to minimise the risk to children.

Under D2.13(a)(v), treads must have a surface or nosing strip which prevents people slipping over and injuring themselves.

In each case the surface or nosing strip must have a slip-resistance classification when tested in accordance with AS 4586. Similar to D2.10(c) there are two tests (the wet pendulum test or the oil-wet inclining platform test) and two conditions (dry or wet) to be considered.

Under D2.13(a)(vi), where a stairway is of a specified height, solid treads must be used so that people cannot see through them. This minimises the risk to people affected by vertigo.

Under D2.13(a)(vii), stairways in Class 9b buildings require a change in direction of at least 30° at specified points. This limits the distance a person can trip or fall down the stairways. This sort of occurrence is more likely to take place in buildings with large numbers of people who are unfamiliar with the building or its stairways.

Under D2.13(a)(viii), winders in lieu of landings are not permitted in a required stairway. Under D2.13(b)(i) winders in lieu of landings are permitted in non-required stairways provided that not more than 3 winders in lieu of a quarter landing or not more than 6 winders in lieu of a half landing are used.

When a stairway discharges directly to a sloping public walkway or road, it is extremely difficult to maintain a constant riser height without setting the stairway back from the walkway. D2.13(c) therefore allows a variation in the riser height in these situations.

See Figure D2.13.

Figure D2.13 Stairway for sloping public walkway or road

Table D2.13

Table D2.13 addresses both public and private stairways, and provides information on acceptable maximum and minimum risers and goings. It also illustrates the method of measuring the rise and going of stairway treads and the maximum gap between treads referred to in D2.13(a)(iv).

Note 2 of Table D2.13 allows the use of a stairway which is curved, or circular in plan view.

The purpose of a landing is to limit the number of risers to provide a rest area for the people using the stairway, and to allow the stairway to change direction if needed.

The maximum grade of 1 in 50 required under D2.14(a) makes sure that the landing is as level as possible, but still allows a slight slope for drainage if necessary.

The minimum length of a landing allows people using the stairway to rest, and reduces the risk of a person falling more than one flight of stairs.

Under D2.14(a)(ii), landings must have a surface or strip at the edge of the landing to prevent a person slipping over and injuring themselves. In each case the surface or edge strip must have a slip-resistance classification when tested in accordance with AS 4586. Similar to D2.10(c) there are two tests (the wet pendulum test or the oil-wet inclining platform test) and two conditions (dry or wet) to be considered.

D2.14(b) provides two options for landings in Class 9a buildings. The aim is to aid the use of a stretcher.

Figure D2.14 illustrates the method of measuring the length of landings as required by D2.14.

Figure D2.14 Method of measuring the length of landings as required by D2.14

It is difficult to see a step or ramp which is too close to a door. People can trip, particularly if the ramp or step is on the opposite side of a door. Figure D2.15(1) illustrates the area where a step is not allowed in a doorway.

Figure D2.15(1) Illustration of where a step is not allowed in a doorway

Concessions are granted in specified circumstances. These include:

• D2.15(a)—in the patient care areas of a hospital; and
• D2.15(b)—in Class 9c buildings; and
• D2.15(c)—in a building required to be accessible by Part D3.
• D2.15(d)—in other buildings, to allow for weatherproofing under an external door.

The threshold of a doorway in a Class 9c building, which is subject to a change in level, may incorporate a ramp and cannot be provided with a step. This is a safety requirement due to the varying mobility of the residents. The ramp may have a maximum slope of 1 in 8 and a maximum height of 25 mm. Figure D2.15(2) illustrates an example of a ramp at a doorway threshold in a residential care building.

Figure D2.15(2) Illustration of ramp at doorway threshold in a residential care building

D2.16 and DP3

This is the Deemed-to-Satisfy Provision for DP3.

D2.16(a) sets out when barriers are required. It should be noted that a barrier is only required where an identified hazard of falling is present. D2.16(b) provides an exemption for the installation of barriers in areas that would be inappropriate due to their inherent functions. These areas include at the perimeter of a stage, rigging loft, loading dock or the like. The reference to 'or the like' could include such areas as the passenger loading points on railway platforms. Other exemptions apply to retaining walls, areas covered by D2.18 and barriers provided to openable windows as required by D2.24.

The following specific provisions applicable to barriers are contained in Table D2.16a

Figures D2.16(1) and D2.16(2) illustrate the various requirements for barriers.

Figure D2.16(1) Illustration of barrier heights and spacings

Figure D2.16(2) Illustration showing when barriers are required

Wire barriers deflect under loading conditions, even when tightly tensioned, and therefore some doubt has been expressed as to whether they can meet the requirements of Table D2.16a 2(c) not to permit a 125 mm sphere to pass through. Also, some concern has been expressed that in time the wire tends to lose its tension and could therefore allow the passage of the 125 mm sphere.

In 2003, the ABCB commissioned research to determine how to overcome these difficulties. The results of this research is contained in D2.16(d).

D2.16(d) allows the use of wire barriers without the need to demonstrate that the barrier would not permit the passage of a 125 mm sphere provided the wire diameter, lay and type, post spaces, etc. are satisfied. If it is proposed to differ any of the specified criteria, then it would be necessary to demonstrate to the approval authority that the Performance Requirement had been satisfied by the use of a Performance Solution.

To assist in the application of D2.16(d), the following terms have been defined:

• Continuous – where the wire spans three or more supports.
• Non-continuous – where the wire only spans between two supports.
• Pulley block – a device consisting of a wheel in which a wire runs around to change its direction.
• Permissible deflection – is the allowable bending of the wire.
• Support rails – are horizontal components of the barrier system that span across the top and bottom to provide structural support.

D2.16(d) provides for three alternative systems, namely—

• horizontal wire systems; and
• non-continuous vertical wire systems; and
• continuous vertical or near vertical wire systems.

For the purpose of D2.16(d), a wire barrier consists of a series of tensioned wire ropes connected to either vertical or horizontal supports serving as a guard to minimise the risk of a person falling from a roof, stairway, raised floor level or the like.

A wire barrier excludes wire mesh fences and the like.

Tables D2.16a and D2.16b contain tension requirements for wires in vertical and horizontal wire barrier systems with varying post spacings, wire spacings and wire types, whereas Table D2.16c only contains deflection requirements for use in horizontal and vertical barrier systems. With the latter, deflection is referred to as an "offset" and is limited to systems that use non-continuous wires. The figures contained in the three tables were derived from testing the spacing combinations in order to prevent the passage of a 125 mm diameter solid cone penetrating between the wires at a predetermined force. The tables also contain additional guidance to ensure that the wire tension will be maintained during the life of the barrier.

For safety, sharp ends of wires at terminations and swages need to be removed and no wire end should protrude more than half the diameter of the wire from the swage or termination fitting.

D2.17 addresses requirements regarding the location, spacing and extent of handrails. Where both barrier and handrail matters require consideration, D2.17 must be read in conjunction with those of D2.16.

D2.17(a)(i) and (ii) set out the location and separation requirements for handrails. For intermediate handrails, see the requirements in D2.9.

D2.17(a)(iii) requires a second handrail located at a practical height between 665 mm and 750 mm in a primary school, to aid children who are generally shorter than adults.

Under D2.17(a)(iv), the height of handrails is a minimum of 865 mm, so that they are comfortable to use for most people and provide adequate stability support and assistance.

D2.17(a)(v) requires a continuous handrail between stair flight landings. It does not apply around a landing between flights, as such a requirement would often be impractical.

Obstructions placed on handrails to prevent people deliberately sliding down them must be considered on a case by case basis to determine whether a hand hold is broken. Ball type stanchions at the top of supports to handrails may be permissible. See Figure D2.17(1).

D2.17(a)(vi) requires handrails in a required exit serving an area required to be accessible, to comply with clause 12 of AS 1428.1, to facilitate use by people with a disability.

The D2.17(b)(i) provisions requiring handrails on at least one side of corridors in a Class 9a building are intended to assist patients.

The D2.17(b)(ii) provisions requiring handrails in corridors in a Class 9c building are intended to assist residents. The handrails are required on both sides of the corridor to assist residents accessing the common areas such as dining rooms and recreation rooms in their day to day living.

D2.17(c) is provided to remind users of the NCC that there are specific requirements for handrails to provide access for people with a disability under Part D3.

D2.17(d) requires handrails on at least one side of a stairway or ramp. The top rail of a barrier could be a handrail. The handrail must extend the full length of the flight or ramp except where the handrail is associated with the barrier, in which case the handrail can terminate where the barrier is allowed to terminate. This would allow for the barriers of geometric stairways such as elliptical, spiral, circular or curved stairways to finish a few treads from the bottom of the stairway. A handrail is not required for winders if a newel post is installed to provide a handhold.

Figure D2.17(1) Illustration of ball-type stanchions

Figure D2.17(2) illustrates the use of handrails complying with D2.17.

Figure D2.17(2) Illustration of handrails complying with D2.17 which form part of a barrier

Some areas are only accessed by maintenance or specialist workers. In such areas, access and egress requirements for members of the public no longer apply, and the requirements are permitted to fall outside the various measurements applying elsewhere.

In Class 2 buildings or Class 4 parts, this includes non-habitable rooms such as attics, storerooms and the like that are not used on a frequent or daily basis. In such cases, the designer has the choice of designing the stair, landing, barrier and handrail to comply with the appropriate provisions of the NCC or with AS 1657.

D2.19 and D2.20 have the same intent

D2.19 should be read in conjunction with D2.20 because its intent is the same.

D2.19 refers to a "doorway serving as a required exit or forming part of a required exit". D2.20 refers to a "door in a required exit or forming part of a required exit". D2.21 refers to a "door in a required exit, forming part of a required exit or in the path of travel to a required exit".

The three different terms have application to doorways and doors in three different situations described below. To understand the differences between these terms, it is necessary to understand what an exit is, as described in the definition of "exit". Also, D1.14 Measurement of distances, provides guidance by describing when the "nearest part of an exit" includes a doorway and when it does not.

The definition of "exit" indicates that stairways (internal or external), ramps and fire isolated passageways are all exits if they provide egress to a road or open space, as are doorways opening to a road or open space and horizontal exits. Stairways and ramps that serve as exits may either be fire-isolated or non-fire-isolated, as determined by D1.3.

D1.14 describes the "nearest part of an exit" for the purpose of measuring distances (prescribed by D1.15), indicating when a doorway is considered to be part of the exit.

The nearest part of the exit is the nearest part of the doorway providing access to a fire-isolated stairway, fire-isolated passageway or fire-isolated ramp, horizontal exit, and a doorway opening to a road or open space. For a non-fire-isolated stairway however, it is the nearest riser, and for a non-fire-isolated ramp, it is the nearest part of the ramped floor. The measurement to the nearest part of a doorway for a fire-isolated exit, horizontal exit and a doorway opening to a road or open space, indicates that the doorway forms part of the exit.

A "doorway serving as a required exit" or a "door in a required exit" means one that is acting as the exit itself, such as the final doorway or door—

• opening to a road or open space; or
• in a horizontal exit.

In this case, the nearest part of the doorway itself is the nearest part of an exit. The doorway or door opening to a road or open space may be a doorway or door from a space or room, or from a corridor.

A "doorway forming part of a required exit" or a "door forming part of a required exit" means a doorway or door that provides access to or is within—

• a fire-isolated stairway or ramp; or
• a fire-isolated passageway.

In this case, the nearest part of the exit is the doorway providing access to the fire-isolated stairway, ramp or passageway. Therefore, any doorway or door that leads into or out of a fire-isolated stairway, ramp or passageway is a doorway or door forming part of a required exit.

A "doorway or door in the path of travel to an exit" is a doorway or door that is not serving as, providing access into, or in, a required exit and does not form part of a required exit. It includes a doorway or door—

• opening from any space in a storey such as an office, conference room, storeroom, sanitary compartment, or the like, into a public corridor (that is not fire-isolated) or open plan public space or the like within the building, or a non-fire-isolated stairway or ramp serving as a required exit; or
• opening from one public corridor into another public corridor or public space within the building.

A doorway or door in a path of travel to an exit is any door, excluding cupboards and service openings, that a building occupant must pass through to reach the exit from the storey.

D2.19(a) applies to all doorways in resident use areas of Class 9c buildings, including doorways in paths of travel to an exit, doorways serving as required exits and doorways forming part of required exits.

Doorways within resident use areas of an aged care building must not be provided with revolving doors, roller shutter doors, tilt up doors or sliding fire or smoke doors. These types of door can impede the movement of residents and also hinder egress from the building.

D2.19(b) applies only to doorways serving as a required exit, or forming part of one, and to doorways in a patient care area of a Class 9a building.

D2.19(b) does not apply to any other doorways (eg a doorway within a path of travel to an exit).

Under D2.19(b)(i), (ii) and (iii), revolving, sliding or tilt-up doors and roller shutters are either prohibited or limited because of their potential to obstruct people evacuating. They can also pose problems if they fail in an emergency.

If people are impeded at a doorway, this can lead to congestion. In an extreme case, it can lead to the crushing of people as they wait for a door to open.

The reason for the concession (subject to specified criteria) for roller shutters or tilt-up doors in small Class 6, Class 7 and Class 8 buildings is that the number of people in the area will be low. Note that this concession does not apply to revolving or sliding doors.

Power-operated doors—D2.19(b)(iv) and D2.19(c)

D2.19(b)(iv) sets out the requirements for power-operated doors in required exits and patient care areas.

D2.19(c) applies to power-operated doors in a path of travel to a required exit. It applies the same provisions for power-operated doors in exits or forming part of an exit contained in D2.19(b)(iv)(A) by specifying the maximum force required to open the door if there is a malfunction or power failure. The reason for this is that a door in a path of travel may also inhibit safe egress if it cannot be readily opened.

The reference in D2.19(b)(iii)(B) and (iv)(A) to a force of 110 newtons is to a relatively small force which most people, including the elderly and the young, could reasonably be expected to use to open a door.

D2.20 and D2.19 have the same intent

D2.20 should be read in conjunction with D2.19 because its intent is the same.

D2.20 applies only to swinging doors in doorways serving as a required exit or forming part of a required exit (eg a doorway leading to, or within a fire-isolated exit). It does not apply to other doorways (eg a doorway within a path of travel to an exit).

Under D2.20(a), egress from a required exit must not be impeded by the swing of a door.

The measurement of the clear width for the safe passage of people evacuating must include any door furniture, such as a door handle.

Doors into a fire-isolated exit are permitted to encroach more than 500 mm as long as they do not impede the path of travel of people already in the exit.

Figure D2.20 illustrates a method of compliance with D2.20(a).

Under D2.20(b), doors are required to swing in the direction of egress to aid evacuation. If a door swings against the direction of egress, the first person to it may not be able to open it because of the pressure of the other people behind them. This could delay evacuation.

D2.20(b) provides a concession (under specified criteria) for small buildings or parts of buildings. The reason for allowing a door to swing against the direction of travel in such buildings is because the number of people likely to use the door will probably be low. This in turn minimises the risk caused by delays induced by opening a door towards the person attempting to gain egress.

D2.20(b)(i) requires these doors that swing against the direction of egress to be fitted with a device for holding the door in the open position. D2.20(b)(i) does not require the door to be fixed in the open position at all times that the building is legally occupied. Although this may be desirable, because of climatic conditions, the weather conditions on a particular day, or for security reasons it may not be possible or desirable for the occupants.

Under D2.20(c), swinging doors must not hamper occupants evacuating.

Figure D2.20 Illustration of door to a fire-isolated stairway complying with D2.20(a)

D2.21 applies to all doors:

• in a required exit (eg an external doorway leading from the building);
• forming part of a required exit (eg a door leading to or within a fire-isolated exit); and
• in a path of travel to a required exit.

“Single hand downward action”

If the opening action of a door latch cannot be a pushing action, it must be a single downward action, capable of being activated with a single hand.

D2.21 prohibits the use of devices such as deadlocks and knobs (where the knobs must be operated in a twisting or similar motion).

This provision takes account of the need for an emergency opening mechanism to be operable by people with a hand or arm related disability, burns to their hands, or with perspiring or wet hands.

The height of the opening device from the floor specified in D2.21 is consistent with that contained in AS 1428.1 “Design for Access and Mobility”. This is a comfortable height for most people to use.

The building regulatory system principally exists to protect the safety, health and amenity of people in buildings. The safety of property, while important, is generally considered to be a secondary matter. D2.21 is designed to maximise the safety of people and prevent them being trapped within a building during a fire.

The risks to people using the building are too great to allow for the use of property security devices, such as deadlocks. Even “after hours” locks, which require human intervention (such as unlocking first thing in the morning and locking last thing at night) to allow egress during times when the public are accessing the building, are not considered to be adequately safe.

In accessible buildings, D2.21(a)(i) requires doors serving areas required to be accessible to have devices that prevent a hand slipping from the handle during the operation of the latch and to have a clearance of between 35 mm and 45 mm from the handle and the back plate or door face. These provisions are designed to allow use of the device by people with a disability.

There are several exceptions to D2.21(a). These include:

• D2.21(b)(i)—strongrooms and vaults, both for security purposes, and the fact that the general public would ordinarily be very unlikely to access such places;
• D2.21(b)(ii)(A)—sole-occupancy units within flats, because the people in the units will generally be in possession of keys to unlock the door;
• D2.21(b)(ii)(B)—sole-occupancy units within motels or hotels, because the people in the units will generally be in possession of keys to unlock the door. However this sub-clause does not include the entrance door to sole-occupancy units in boarding-houses, guest houses, hostels, lodging-house or backpackers accommodation as the occupant may not always have possession of keys to unlock the door;
• D2.21(b)(ii)(C)—small sole-occupancy units in Class 5–8 buildings, where it would be difficult to overlook the presence of anyone at closing time; and
• D2.21(b)(ii)(D)—restricted access spaces and rooms otherwise inaccessible to people at all times, such as cleaners’ rooms and the like.

D2.21(b)(iii) provides for special arrangements to be made where particular security issues arise including Australian Government Security Zones 4 and 5. If this option is taken, the appropriate authority will need to be satisfied that, in the event of an emergency, access to exits will be enabled immediately with effectively no time delay.

Where the option for human control is exercised under D2.21(b)(iii)(D), the person controlling the unlocking system MUST be available at ALL times while the building is lawfully occupied. It is not acceptable for the system to be left uncontrolled. Nor is it acceptable for that person to be absent from the control post while carrying out any other work duties. A beeper or some other type of personally carried device warning of an emergency is not adequate to effect immediate opening of the locked doors. If the controlling person is absent for any reason, there must be a process enabling their relief by an equally trained person.

D2.21(b)(iv) provides an exemption for buildings fitted with automatic “fail-safe devices”, where the devices are activated by another active system.

In this case, the appropriate authority must be satisfied that:

• the device is genuinely “fail-safe” (while not specifically referenced in D2.21(b)(iv), this would include during power failures); and
• in the event of an emergency, access to exits will be enabled immediately, with effectively no time delay.

Egress from Class 9b buildings is a complex issue. They are often accessed by the general public, and include buildings which have people unfamiliar with their surroundings. This environment is not conducive to orderly or easy evacuation especially in places such as cinemas, theatres, sporting complexes and nightclubs.

D2.21(c) makes special provision for those which accommodate more than 100 people.

D2.21(c) differs from the usual D2.21 provisions in that:

• it prohibits the use of a door handle type opening device (other than a bar) or other device (including levers or knobs) requiring more than a pushing action; and
• it applies to only one door leaf of a two-leaf door set. However, the other door must also swing open if it is needed to satisfy the required width of egress.

The provisions of D2.21(c) do not apply to schools, early childhood centres, or buildings such as churches, mosques and temples used for religious purposes. Such buildings must comply with D2.21(a).

Schools and early childhood centres are excepted because:

• the occupants are under almost constant adult supervision;
• most schools have a communication system with which occupants are familiar;
• most occupants are adequately controlled enabling easier evacuation; and
• they are used during daylight hours, and door handles and their function are more easily identified and familiar to occupants.

Required fire doors must be tested as a complete unit, including the frame and furniture. The test on a fire door installed in an exit, or forming part of an exit, includes the opening devices to be used to comply with D2.21.

It is not unknown for a fire-isolated exit to become unusable during an emergency. In high-rise buildings, hospitals and Class 9c buildings people must be able to leave the exit and proceed to an alternative exit to evacuate. It is unlikely that the second exit will also be unusable.

One option is for a person in a fire-isolated stairway to enter a storey and gain access to the alternative exit through that storey.

D2.22(a)(iii) applies to the whole fire-isolated exit serving a storey above an effective height of 25 m. This means that a fire-isolated exit serving a storey below an effective height in a building with an effective height 25 m or greater, is treated the same as one in a building with an effective height of less than 25 m, provided it does not also serve a storey that is located above an effective height of 25 m.

It should be noted that if a fire-isolated passageway serves two stairways, one of which serves a storey above an effective height of 25 m, then D2.22(a)(iii) will apply, i.e. the doors cannot be locked from the inside.

Figure D2.22 Illustration of exits serving storeys above and below an effective height of 25 m

Under normal conditions of use, it is also possible that a person may mistakenly enter a fire-isolated exit. That person should not be required to travel all the way down the stairway to be able to leave it, especially in a high-rise or Class 9c building.

The ability to enter at each floor of a building could be unnecessary and lead to a breach of a building’s security. Accordingly, entry at every fourth floor (under D2.22(b)(i)) will achieve the intent of this provision, without significantly interfering with the building’s security. Where this option is taken, all doors must be openable by a fail-safe device activated by a fire alarm.

An alternative method of minimising the risk of a person being trapped in a fire-isolated stairway is to provide an intercommunication system under D2.22(b)(ii). Where this option is taken, all doors must be openable by a fail-safe device activated by a fire alarm.

The doors referred to in D2.23(a) are all required for evacuation in an emergency. Their obstruction could result in the death of people attempting to evacuate.

Fire and smoke doors are designed to minimise the risk to people inside a fire compartment and a fire-isolated exit. A door kept open in a storey experiencing a fire could result in the emergency exit becoming unusable, or could aid the spread of fire and/or smoke to other parts of the building. If all exits are affected, people will have no way of evacuating the building.

The intent of D2.24 is to limit the risk of a person (especially a young child) falling through an openable window. Where the floor level below an openable window is less than 2 m there are no specific requirements. For an openable window in a bedroom of a Class 2 or 3 building or Class 4 part of a building or in a Class 9b early childhood centre 2 m or more above the surface beneath, openable windows are required to restrict the passage of a 125 mm sphere using any one of the following design solutions:

• The window be designed such that any opening does not allow a 125 mm sphere to pass through (e.g. louvres).
• The window be fitted with a fixed or dynamic device that is capable of restricting the window opening so it does not allow a 125 mm sphere to pass through and is difficult for a young child to operate. The restricting device must be capable of resisting a 250 N force when directed against the window such as a casement window or in attempting to push a sliding window open. An internal screen with similar parameters may be installed.
• The window be fitted with an internal or external screen that does not allow a 125 mm sphere to pass through and which must resist a horizontal outward force of 250 N.

If the openable part of a window is at least 1.7 m above the floor, no further protection is required.

D2.24(b)(ii)(C) relates to a screen or window restricting device protecting an openable window in a bedroom of a Class 2 or 3 building or Class 4 part of a building or in a Class 9b early childhood centre. The screen or opening restricting device may be installed in a manner that allows it to be removed, unlocked or overridden in the event of a fire or other emergency to allow safe egress. In these situations the unlocking device must be child resistant.

Child resistance could be achieved through the use of a tool, key or two hands.

There are a number of hardware options available. Short chain winders and barrier screens will allow windows to comply with this requirement. Sliding window locks may lock a sash so a 125 mm sphere cannot pass through. Where provision is made to fully open the window beyond 125 mm then the child resistant release mechanism is required in addition to the device resisting a 250 N force as required by D2.24(b)(ii)(B).

D2.24(c) in addition prescribes that an 865 mm barrier (sill) would be required. A wall beneath an openable window can be considered as the barrier if the criteria in (d) are met.

D2.24(c)(ii) relates to the height of a barrier under an openable window that is not in a bedroom in a Class 2 or 3 building or a Class 4 part of a building.

The term 'window' is not italicised in D2.24 and as such, is not restricted to the definition of 'window' in the NCC. The reason for this is to also capture windows that may let in air but not light, e.g. metal louvres. A metal louvre or openable panel would not fit in the NCC definition of window but is subject to the window barrier provisions.

D2.2 sets the criteria for the materials and methods of construction used in stairways and ramps within a fire-resisting shaft. The provision provides requirements for maintaining the integrity of the fire protection to the shaft of a fire-isolated stairway and ramp, by requiring a stairway or ramp to be constructed of non-combustible materials to ensure that if there is local failure it will not impair the fire-resistance of the shaft.

D2.25 provides a concession to the requirements of D2.2 allowing timber treads, risers, landings and associated supporting framework to be used within a fire-isolated stairway or fire-isolated passageway constructed of fire-protected timber provided:

• the timber treads, risers, landings and associated supporting framework meets certain material requirements;
• the building is provided with a sprinkler system (including within the fire-isolated stairway or passageway); and
• 13 mm fire-protective grade plasterboard is installed to the underside of flights and landings located directly above a landing level which is at or near the level of egress or provides direct access to car parking levels.

D2.25 applies to a fire-isolated stairway or fire-isolated passageway constructed of fire-protected timber, therefore the limitations of C1.13 apply. These limitations include a maximum effective height of 25 m and application only to Class 2, 3 and 5 buildings.