Balustrades on a deck: the heights and gaps the code sets
Under the National Construction Code’s Housing Provisions, a deck needs a continuous barrier along its side where it is possible to fall 1 m or more to the surface beneath, and that barrier must be not less than 1 m above the deck floor. Openings in it must not let a 125 mm sphere pass through. For higher decks the code adds: “Where it is possible to fall more than 4 m, any horizontal elements within the barrier between 150 mm and 760 mm above the floor must not facilitate climbing.”
This guide quotes the code; it isn’t engineering or building advice for your deck. The official text is the ABCB’s Housing Provisions, Part 11.3, and your certifier can confirm what applies to your project.
Which code, and which edition
The clauses on this page are quoted from Part 11.3, Barriers and handrails, of the ABCB Housing Provisions in NCC 2022. The National Construction Code’s Volume Two covers Class 1 buildings, which WoodSolutions says take in houses that stand alone, villas and townhouses, and Class 10 structures, garages, sheds and swimming pools among them.
The ABCB’s adoption table lists 1 May 2027 as the date New South Wales adopts NCC 2025, and warns that some requirements may apply at different times, or not at all, because of state and territory variations. The NSW schedule of variations to the 2022 Housing Provisions lists no NSW variation to Part 11.3. Ask your certifier which edition applies to your approval.
Each clause below is quoted word for word, inside quotation marks. The quotation pauses where the code points to one of its own figures or opens a list with a dash. The key under the drawing is a pointer to the clauses, not a replacement for them.
The five measurements, drawn
- 1Barrier height: not less than 1 m above the floor of a deck. 11.3.4(2)
- 2Openings must not permit a 125 mm sphere to pass through. 11.3.4(4)
- 3The band between 150 mm and 760 mm above the floor, where horizontal elements must not facilitate climbing if it is possible to fall more than 4 m. 11.3.4(8)
- 4The fall: a barrier is required where it is possible to fall 1 m or more to the surface beneath. 11.3.3(1)
- 5A barrier fixed to the vertical face of a deck’s edge: the opening between barrier and face must not exceed 40 mm. 11.3.4(5)
When a barrier is required
(1) “A continuous barrier must be provided along the side of a trafficable surface, such as”:
- “a stairway, ramp or the like; and”
- “a floor, corridor, hallway, balcony, deck, verandah, mezzanine, access bridge or the like; and”
- “a roof top space or the like to which general access is provided; and”
- “any delineated path of access to a building,”
“where it is possible to fall 1 m or more measured from the level of the trafficable surface to the surface beneath”.
(2) “The requirements of (1) do not apply to”: (a) “a retaining wall unless the retaining wall forms part of, or is directly associated with, a delineated path of access to a building from the road, or a delineated path of access between buildings”; or (b) “a barrier provided to an openable window covered by 11.3.7 and 11.3.8.”
Quoted from the ABCB Housing Provisions 2022. The words inside quotation marks are the code’s own; a colon outside them stands in for one of its dashes, and its pointers to its figures are left out.
The code explains why the rules are written as they are: “Children are at particular risk of falling off, over or through ineffectively designed or constructed barriers. Accordingly the requirements of this Part aim to ensure that a barrier reduces the likelihood of children being able to climb over a barrier or fall through a barrier.”
How high
(2) “The height of a barrier must be in accordance with the following:”
- “The height must not be less than 865 mm above the nosings of the stair treads, the floor of a ramp or the like”.
- “The height must not be less than”: (i) “1 m above the floor of any landing, corridor, hallway, balcony, deck, verandah, access path, mezzanine, access bridge, roof top space or the like to which general access is provided”; or (ii) “865 mm above the floor of a landing to a stairway or ramp where the barrier is provided along the inside edge of the landing and does not exceed a length of 500 mm.”
(3) “A transition zone may be incorporated where the barrier height changes from 865 mm on the stairway flight or ramp to 1 m at the landing”.
Quoted from the ABCB Housing Provisions 2022. The words inside quotation marks are the code’s own; a colon outside them stands in for one of its dashes, and its pointers to its figures are left out.
Gaps and openings
(4) “Openings in barriers (including decorative balustrades) must be constructed so that they do not permit a 125 mm sphere to pass through it and for stairways, the opening is measured above the nosing line of the stair treads”.
(5) “Where a required barrier is fixed to the vertical face forming an edge of a landing, balcony, deck, stairway or the like, the opening formed between the barrier and the face must not exceed 40 mm.”
(6) “For the purposes of (5), the opening is measured horizontally from the edge of the trafficable surface to the nearest internal face of the barrier.”
Quoted from the ABCB Housing Provisions 2022. The words inside quotation marks are the code’s own; its pointer to one of its figures is left out.
Clause 11.3.4(7) relaxes the opening rule only for a stairway serving a non-habitable room, such as an attic or storeroom that is not used on a regular or daily basis. It does not apply to a deck.
Climbable elements
(8) “Restriction on horizontal elements:”
- “Where it is possible to fall more than 4 m, any horizontal elements within the barrier between 150 mm and 760 mm above the floor must not facilitate climbing.”
- “For the purpose of (a), the 4 m is measured from the floor level of the trafficable surface to the surface beneath.”
Quoted word for word from the ABCB Housing Provisions 2022.
The code sets this rule for falls of more than 4 m. The 125 mm opening rule above applies to every barrier the code requires, apart from the stairway exception in 11.3.4(7).
Wire, glass and strength
- Wire. A barrier constructed of wire is deemed to meet the 125 mm rule if it is built in accordance with clause 11.3.6, which sets tension or deflection values by wire diameter, wire spacing and the clear distance between posts. Those tables are long; they are in the code itself.
- Glass. Clause 11.3.4(10): “A glass barrier or window serving as a barrier must comply with H1D8 and the relevant provisions of this Part.”
- Strength. Clause 11.3.4(11): “A barrier, except a window serving as a barrier, must be designed to take loading forces in accordance with AS/NZS 1170.1.”
Handrails on deck stairs
(1) “Handrails to a stairway or ramp must”: (a) “be located along at least one side of the stairway flight or ramp; and” (b) “be located along the full length of the stairway flight or ramp, except in the case where a handrail is associated with a barrier the handrail may terminate where the barrier terminates; and” (c) “have the top surface of the handrail not less than 865 mm vertically above the nosings of the stair treads or the floor surface of the ramp”; and (d) “be continuous and have no obstruction on or above them that will tend to break a handhold, except for newel posts, ball type stanchions, or the like.”
(2) “The requirements of (1) do not apply to”: (a) “a stairway or ramp providing a change in elevation of less than 1 m; or” (b) “a landing; or” (c) “a winder where a newel post is installed to provide a handhold.”
Quoted from the ABCB Housing Provisions 2022. The words inside quotation marks are the code’s own; a colon outside them stands in for one of its dashes, and its pointers to its figures are left out.
Keeping a balustrade safe
Building Commission NSW says: “Balconies, decks, balustrades and railings must be built to the Building Code of Australia and relevant Australian Standards. They must be inspected and maintained regularly for safety.” WoodSolutions suggests an annual inspection of decks, steps and balustrades, checking fixings, coating and movement. The maintenance guide sets out the rest.
If you rent
NSW Fair Trading says to record any fault or damage, decks and balconies included, on the condition report at the start of a tenancy, and that a tenant should tell the landlord or agent as soon as possible when something breaks or needs fixing during the tenancy. Landlords must keep a rented home in a reasonable state of repair.