BCA Section D – Access and Egress: Comprehensive Study Notes
1 Introduction
1.1 General Principles
Buildings must have enough exits to allow safe evacuation in an emergency.
Exit systems consist of paths of travel to exits, and exits comprising doors, stairs and passageways, that provide a clear, unobstructed path to a road/open space or to a place of safety inside the building with access to an exit.
Exit/egress systems must support Fire Brigade intervention/operation requirements.
Paths of travel to exits should be easily negotiated and clear of obstructions.
Fire isolated exits (stairways/ramps) serve as places of relative safety where occupants can seek refuge and move to open space; these paths should allow between-storey movement and support Fire Brigade operations (hydrants, hose reels, search and rescue).
Access and egress is addressed in Section D of the Building Code of Australia (BCA).
Objective of Section D: provide, as far as reasonable, safe, equitable and dignified access to a building, and safeguard occupants during evacuation.
The notes give an overview of the main concepts of Section D and snapshots of relevant Performance Requirements for performance solutions and Fire Engineered Solutions.
The notes are educational, not a substitute for the BCA; they reflect intent but do not reproduce detailed BCA requirements.
1.2 Topic Objectives
(a) Understand the concept of access and egress in building regulations.
(b) Apply knowledge of the practical design process used by the industry.
1.3 BCA Objectives
Objective of Section D: to provide safe, equitable and dignified access to a building and its services, while safeguarding occupants during evacuation.
The ABCB Guide to the BCA provides guidance on key phrases:
‘as far as is reasonable’ means provisions are not absolute (in line with Disability Discrimination Act).
‘equitable’ combines fairness and equality, not necessarily identical capabilities for everyone.
‘dignified’ means access to and within a building and its services/facilities in a non-degrading manner.
‘safeguarding people evacuating’ includes people with disabilities who may require special egress arrangements.
1.4 Performance requirements
Compliance with the BCA performance requirements can be achieved by:
a Performance Solution,
or a deemed-to-satisfy (DTS) solution, or a combination of both as per Part A of the BCA.
D2D (Section D) contains nine performance requirements. Summaries:
D1P1: Safe access for people to and within all services and facilities, as far as reasonable.
D1P2: Safe gradients, doors, stairways and ramps; slip-resistant walking surfaces; handrails; ramp landings; safe stair passage.
D1P3: Barriers to prevent falls through openings or between levels.
D1P4: Number, dimensions and distribution of exits; consider evacuation time for occupants.
D1P5: Fire-isolated exits to enable safe evacuation past a storey on fire, aid fire brigade access, and minimize travel from fire-affected areas to a safe place.
D1P6: Paths of travel to an exit with appropriate dimensions for occupants.
D1P7: If an evacuation lift is used, its number/design must suit travel distance, occupant characteristics, building use and design.
D1P8: Parking spaces suitable for people with disabilities.
D1P9: Inclusion of hearing augmentation systems where inbuilt audible systems are used.
1.5 The DTS provisions
The DTS provisions in Section D are divided into four parts:
Part D1 – Access and Egress,
Part D2 – Provision for Escape,
Part D2 (construction of exits) – (note: text refers to D3; see context below),
Part D3 – Access for People with Disabilities.
This section also contains Objective and Functional statements outlining the intended outcomes.
Complying with the DTS provisions in Part D1, D2, D3 and D4 ensures compliance with the Performance Requirements of the BCA. Key principles are discussed in Section 3.
2 Part D2 (Provision for Escape)
2.1 Escape provisions
Part D2 and Part D3 deal with escape provisions from buildings.
Exit definition (BCA):
(a) Any or any combination of the following that provide egress to a road/open space:
i. An internal or external stairway
ii. A ramp
iii. A fire-isolated passageway
iv. A doorway opening to a road or open space
(b) A horizontal exit or a fire-isolated passageway leading to a horizontal exit.
Exit system design depends on:
(a) The number of storeys connected by the exit,
(b) The classification of the building/part,
(c) The rise in storeys,
(d) The layout of a storey and travel distance to an exit or point of choice,
(e) The number of persons accommodated.
Design checklist when designing an exit system:
(a) Classify the building – Part A6
(b) Determine the number of exits required – D2D3
(c) Determine whether exits must be fire isolated – D2D4
(d) Determine whether travel distance complies – D2D5, D2D19, D2D20
(e) Ensure distances between ‘alternative exits’ comply – D2D6
(f) Determine number of persons accommodated – D2D18
(g) Calculate the aggregate exit width required – D2D8
Worked example 1 (Number of exits required – D2D3)
(a) Information: Residential flat building with basement parking; 11 storeys above ground; 3 storeys below ground; internal height/storey = 3 m
(b) Task: Determine number of exits required per D2D3
(c) Answer steps:
Classification (Part A6) = Class 2 and 7a
Minimum number of exits per storey (D2D3) = 1
Effective height > 25 m; minimum exits per storey = 1
2 exits required per storey for Class 2 to satisfy D2D3 – Yes
2 exits required per storey for Class 7a to satisfy D2D3 – Yes
2.2 Fire isolated exits (D2D4)
1.2.1 In some cases, the BCA requires fire-isolated exits; higher-rise buildings have greater evacuation risk, so the fire-isolated exit requirement correlates with storey count.
1.2.2 Typically required where a rise in storeys is three or more, but conditions under D2D4 may require fire isolation with a rise in storeys of two in certain circumstances.
1.2.3 Exits that are fire isolated are enclosed in fire-resisting construction (FRL) determined under Part C; doorway and penetrating services are protected per Part C4.
1.2.4 Fire isolated exits provide occupants with a relative safety area, enabling vertical movement and evacuation as well as safe access for Fire Brigade interventions.
1.2.5 Key characteristics of fire isolated exits include:
(a) Fire-resisting construction bounding the exit (stairway/ramp) (fire isolated shaft)
(b) Fire-rated doors protecting doorway entries
(c) Limitations on services within the exit
(d) Internal hydrants located in the exit
(e) Restrictions on entry/exit and re-entry to the building
1.2.6 For class 2 and 3 buildings, every required exit must be fire isolated unless it connects/passes through or by not more than specific storeys with buildings and/or sprinkler protection (see D2D4 for details):
(a) Class 2: 3 consecutive storeys allowed non-fire-isolated; or 2 consecutive storeys with limitations; exceptions for motor vehicles/ancillary use; or where sprinkler system installed throughout.
(b) FRL and construction requirements depend on whether the extra storey is separated by fire-resistant construction with specific FRLs and no openings for fire passage.
1.2.7 For Class 5–9 buildings, fire isolation requirements have additional conditions and exceptions similar to the above (sprinkler provisions, FRLs, and separation considerations).
1.2.8 Worked example 2 (Are exits required to be fire isolated – D2D4)
(a) Use Worked example 1 building
(b) Task: Determine whether exits must be fire isolated
(c) Answer steps:
Class 2 storeys connected/passed through greater than four storeys – yes
Exits serving Class 2 must be fire-isolated – yes
Class 7a storeys connected/passed through 3 storeys – no (due to assumptions) with sprinklers – yes, building protected by sprinklers; exits serving Class 7a not required to be fire isolated in this example.
1.3 Travel Distance
Travel distance is the worst-case distance a person on a storey would travel to reach an exit; not defined explicitly in the BCA, but maximum permissible distances exist by building type and occupant characteristics.
1.3.2 D2D5 sets the maximum travel distance to an exit or a point of choice to two or more exits; D2D19 and D2D20 provide measurement rules.
1.3.3 D2D2 excludes internal parts of sole-occupancy units in Class 2/3 buildings or Class 4 parts from travel distance limits.
1.3.4 Determining compliance requires considering building class, storey layout, fixtures, furniture, exit type, and exit location.
1.3.5 D2D5(1) for sole-occupancy units in Class 2/3 buildings: a) 6 m rule: maximum distance from any sole-occupancy unit doorway to an exit or to a point where travel in two directions to 2 exits is available; b) 20 m rule for single-exit scenarios at the level of egress to road/open space.
1.3.6 Example (Figure 1): Five-storey Class 2 residential; travel distance to arrive at an exit or to a point allowing two-exit travel exceeds 6 m; redesign needed (add another exit) to comply with D2D5.
1.3.7 Travel distance for the upper-storey floor in the example is measured from the doorway of the worst-case SOU; non-compliant; redesign performed (add exits or layout changes).
1.3.8 Class 4 parts: doorway distance to exit must be not more than 6 m from an exit or from a point where two-exit travel is possible.
1.3.9-1.3.12 For Class 5–9 buildings, maximum distances: no point more than 20 m from an exit or from a point where two-exit travel is available; the maximum distance to one exit must not exceed 40 m; concessions exist (e.g., 30 m for some Class 5/6 buildings with single exit at road level); Class 9a hospitals have tighter limits; other class-specific notes and figures provided (Figure references).
1.3.7–1.3.13 include figures and additional examples illustrating travel distance concepts in Class 2, Class 5, and Class 9a contexts.
1.4 Distance between alternative exits
Exits serving as alternative exits to one another when travel distances (per D2D5) require an additional exit or where two exits are required.
D2D6 requires:
alternative exits distributed as uniformly as practicable,
not less than apart, not more than apart in a Class 2/3 building or a patient care area in Class 9a; and not more than apart in all other cases,
alternative paths must not converge so that they become less than apart.
Exits should be placed so a person can readily find the alternative exit if the first exit is unusable; distance between exits is measured as a straight-line distance between nearest parts of the exits; the shortest path is used even if it curves via corridors (D2D20).
Figure 3 example illustrates measurement considerations.
1.5 Aggregate exit width
The total exit width required from a storey is calculated under D2D8 based on the number of persons deemed to be accommodated under D2D18.
1.5.2 D2D18: determining number of persons accommodated: sum of floor areas of parts of the storey divided by the m²/person value for that use (Table D2D18), excluding spaces set aside for lifts, stairs, ramps, escalators, corridors, lobbies, ducts, sanitary compartments, etc.
1.5.3 Worked example 3 (Number of persons accommodated – D2D18)
(a) Class 6 restaurant on ground floor of a five-storey building; gross restaurant area 400 m²; assume spaces set aside 70 m².
(b) Net floor area = 400 − 70 = 330 m².
(c) For a restaurant: m²/person = 1 (Table D2D18).
(d) Classification (A3.2) = Class 2 and 7a.
(e) Number of persons accommodated = 330 / 1 = 330 persons.
1.5.4 Exits must have minimum unobstructed width not less than 1 m for each exit/path to an exit (D2D9 details);
1.5.5 D2D7 requires unobstructed height not less than throughout, except doorway unobstructed height may be reduced to (1980 mm).
1.5.6 Aggregate exit width (D2D8) definition and dependency on number accommodated; calculations adjust as occupancy grows beyond 200 persons.
1.5.7 If storey/mezzanine accommodates more than 200 persons, aggregate unobstructed width increases per D2D8 (e.g., 2 m plus 0.5 m per 75 persons over 200 for stair/ramp changes) or equivalent rules for other configurations.
1.5.8 D2D9 specifics: unobstructed width of each doorway may be reduced by 0.25 m (250 mm) while ensuring minimum doorway width remains; examples show two-door vs three-door configurations.
1.6 Travel via exits and to public road
1.6.1 D2D12: a doorway from a room must not open directly into a stairway/passageway/ramp that is fire-isolated unless the doorway opens to a public corridor or lobby, or to a sole-occupancy unit occupying the storey, or to a sanitary compartment/airlock.
1.6.2 Each fire-isolated stairway or ramp must provide independent egress from each storey served and discharge directly (or via its own fire-isolated passageway) to one of the allowed areas including a road or open space (D2D12).
1.6.3 D2D12 requires that the path of travel from a fire-isolated exit be protected when it passes within of the same building measured at a right angle; protection requires external wall construction with not less than FRL and openings protected per C4D5 (to maintain tenability of occupants).
1.6.4 D2D13 permits the use of an external (ventilated) stair in lieu of a fire-isolated stair in certain cases (storey < 25 m effective height). It requires positioning not less than from the building, and where within 6 m, strict shielding walls and opening requirements apply (consult D2D13).
1.6.5 D2D14 requires continuous means of travel by non-fire-isolated stairs or ramps from every storey to the egress level; stairs must provide unbroken flights and landings to the exit level.
1.6.6 D2D15 deals with getting to the public road after leaving the building: if an exit leads to open space, the path to the road must have unobstructed width at least equal to the exit width (or , whichever is greater).
1.6.7 If open space is on a different level from the public road, the path to the road must be a ramp or incline with gradient not steeper than (or not steeper than if required by DTS in Part D3) or a stair that meets DTS requirements for the BCA (except if the Class 9a building requires a ramped egress).
1.6.8 D2D23 (Class 9b primary school): must be located at a level with direct egress to a road/open space; exception when Rise in Storeys ≤ 4 and only use in the building; if more complex, a Performance Solution may be needed.
1.6.9 The 2022 BCA includes specific compliance requirements for early childhood centers and multi-storey childcare; highlights include: at least two exits per storey or fire compartment; fire-isolated exits required where Rise in Storeys > 2; fire compartmentation and spacing to facilitate horizontal egress; balustrade design guidance for fire-isolated stairs; re-entry provisions from fire-isolated stairs.
Worked examples in this section:
Worked example 2 (Are exits required to be fire isolated – D2D4): See 1.2 above for scenario details and conclusions about fire isolation requirements based on class, height, and sprinkler presence.
Worked example 3 (Number of persons accommodated – D2D18): See 1.5.3 for calculation using net floor area and Table D2D18 values; demonstrates determining occupancy to size aggregate exit width.
Worked example 4 (Exit width – D2D8): Demonstrates calculating aggregate exit width for a restaurant scenario with >200 occupants; shows calculation steps to arrive at an aggregate width (e.g., 3.0 m in the example).
Worked example 5 (Exit width – D2D9): Demonstrates distributing width among two or three doors after subtracting 0.25 m from each door to get unobstructed effective width.
3 Part D3 (Construction of Exits)
3.1 Exit construction
2.1 (D3) discusses construction of exits; D3D2 (the application clause) states that some parts of Part D3 do not apply to internal parts of a sole-occupancy unit in Class 2/3 buildings or Class 4 parts.
The following notes summarize the main requirements; not exhaustive of all DTS provisions.
2.2 Doors and doorways (D3D16–D3D25)
2.2.1 D3D16 regulates doorway thresholds: a step or ramp must be no closer to the doorway than the width of the door leaf unless the doorway opens to a road/open space/external landing, and door sill is not more than above the ground surface.
2.2.2 D3D24 largely prohibits revolving doors for required exits; tilt-up doors/roller shutters are restricted unless serving certain small/classified buildings; sliding doors and power-operated doors are regulated.
2.2.3 D3D25 states swinging doors in a required exit must not encroach more than into the required width; also governs door swing direction with exceptions (e.g., when only one exit is available and door is held open, or for sanitary compartments/airlocks).
2.2.4 D3D25 also notes doors serving as exits from the building must comply; D3D25 does not apply to doors leading into sole-occupancy units.
2.3 Operation of Latch (D3D26)
Doors in a required exit must be readily openable without a key from the egress side by a single hand downward or pushing action on a device located between and above floor.
D3D26 exempts certain doors (e.g., doors serving sole-occupancy units in Class 2/3 buildings, spaces inaccessible when locked, or doors with unlocking arrangements for security).
D3D26 restricts lock/latch types for doors in exits; conventional knobs are not acceptable for compliant exits.
2.4 Stairs
2.4.1 Exits (stairways or ramps) must be fire-isolated under D2D4 or designed to align with D2D5 travel-distance considerations and provided with a path that leads to a road/open space.
2.4.2 D3D5 requires no direct connection between a lower flight reaching a road/open space from below to a higher flight from above; this prevents a person from moving down to a basement via a route that re-enters at ground level.
2.4.3 Separating construction within stairs must be non-combustible and smoke-proof when a single shaft connects rising and descending flights; separate shafts must be fire separated.
2.4.4 D3D9 regulates space under non-fire-isolated stairs: enclosure of space below stairs must have FRL at least and a self-closing fire door if the space is enclosed; these provisions do not apply to internal parts of a Class 2/3/4 residential sole-occupancy unit. The underside of a fire-isolated stair cannot be enclosed as a cupboard.
2.4.5 D3D14 regulates goings (treads) and risers:
A stairway must have not more than or less than risers per flight.
Going and rise dimensions must be constant along a flight.
Openings in risers must prevent a diameter sphere from passing through.
Treads must have non-slip surface or non-skid edge near nosings.
2.5 Balustrades (D3D17–D3D21)
Balustrads should be continuous for the full hazard extent, with appropriate height to prevent falls and with sufficient strength, rigidity and load resistance.
Typical heights: at balconies/landings: ; on stairways: above nosings; openings must not permit a sphere to pass through.
For floors more than above ground, horizontal or near-horizontal elements between and above floor should not facilitate climbing.
2.6 Openings to balustrades to fire-isolated stairways
In certain instances, openings must be limited to not more than ; rails must be provided at heights no greater than above stair nosings; gaps between rails must not exceed There are cases where railing types are not permitted (e.g., in early childhood centers and external stairs used instead of handrails).
3 Part D4 (Access for people with disabilities)
3.1 Access
3.1.1 Part D4 covers requirements for people with disabilities; D4D2 is the application clause.
Part D4 recognises AS 1428.1 – Design for Access and Mobility; General requirements for access in buildings are provided in Table D4D2a and Table D4D2b.
4 Conclusion
4.1.1 Buildings must have sufficient exits to enable safe evacuation; exits/paths should lead to a road/open space or a safe internal area and support Fire Brigade intervention.
4.1.2 Paths of travel to exits should be negotiable and unobstructed; fire-isolated exits function as safe refuges where occupants can move to open space, and enable Fire Brigade access to carry out rescue operations.
4.1.3 The DTS provisions are organized into Part D1 (Access and Egress), Part D2 (Provision for Escape), Part D2 (Construction of Exits) and Part D3 (Access for People with Disabilities); the design/process highlights in Sections 3 and 4 summarize key principles for compliance.
5 References
Australian Building Codes Board (2022). The National Construction Code: Building Code of Australia 2022 Volume One. Canberra.
Australian Building Codes Board (2019). The National Construction Code: Guide to Volume One. Canberra.
Note: The notes above mirror the content and examples provided in the transcript, including the worked examples and specific numerical values for distances, heights, and widths, as well as the definitions and requirements for fire-isolated and non-fire-isolated exits, travel distances, and aggregate exit widths.