StandAId › NCC explained › Stair construction and barriers to prevent falls in a house
Stairs and balustrades are where houses fail inspections most often, because the numbers are unforgiving. Risers and goings have to sit inside set ranges and be consistent through a flight, landings are required at set intervals, and any trafficable surface where it's possible to fall 1 m or more needs a barrier of the right height with openings small enough that a child can't fall through or climb.
The NCC's Housing Provisions cover both the stair geometry (Part 11.2) and the barriers (Part 11.3). Volume Two's performance clause sits above them.
The clauses below are the core deemed-to-satisfy provisions; read them together — a compliant stair with a non-compliant balustrade is still a fail.
This page is a plain-English guide written by StandAId, followed by the actual NCC 2025 clause text. It is not professional advice and StandAId is not endorsed by the ABCB — always check the current edition on ncc.abcb.gov.au and your state's requirements.
(1) A stairway must be designed to take loading forces in accordance with AS/NZS 1170.1 and must have—
(a) not more than 18 and not less than 2 risers in each flight; and
(b) goings (G), risers (R) and a slope relationship quantity (2R + G) in accordance with Table 11.2.2a, except as permitted by (2) and (3); and
(c) constant goings and risers throughout each flight, except as permitted by (3) and (4), and the dimensions of goings (G) and risers (R) in accordance with (1), (2) and (3) are considered constant if the variation between—
(i) adjacent risers, or between adjacent goings, is not more than 5 mm; and
(ii) the largest and smallest riser within a flight, or the largest and smallest going within a flight, is not more than 10 mm; and
(d) risers which do not have any openings that would allow a 125 mm sphere to pass through between the treads; and
(e) treads of solid construction (not mesh or other perforated material) if the stairway is more than 10 m high or connects more than 3 storeys.
(2) In the case of a stairway serving only non-habitable rooms, such as attics, storerooms and the like that are not used on a regular or daily basis—
(a) the going (G), riser (R) and slope relationship quantity (2R + G) in accordance with Table 11.2.2a may be substituted with those in Table 11.2.2b; and
(b) need not comply with (1)(d).
(3) In the case of a stairway with winders —
(a) a maximum of 3 consecutive winders in lieu of a quarter landing in a flight and a maximum of 6 consecutive winders in lieu of a half landing in a flight; and
(b) the going (G) of all winders in lieu of a quarter or half landing may vary from the going of the straight treads within the same flight provided that the going (G) of such winders is constant.
(4) The point of measurement of the going (G) in the slope relationship quantity (2R + G) for tapered treads and treads in spiral stairways as described in Table 11.2.2a (see Figure 11.2.2a, Figure 11.2.2b and Figure 11.2.2c) must be—
(a) for tapered treads, other than treads in a spiral stairway —
(i) not more than 1 m in width, the middle of the unobstructed width of the stairway (see Figure 11.2.2b); and
(ii) more than 1 m in width, 400 mm from the unobstructed width of each side of the stairway (see Figure 11.2.2c); and
(b) for treads in spiral stairways, the point seven tenths of the unobstructed width from the face of the centre pole or support towards the handrail side (see Figure 11.2.2d and Figure 11.2.2e).
(5) Riser and going dimensions must be measured in accordance with Figure 11.2.2f.
[See Table 11.2.2a — Riser and going dimensions (mm)]
[See Table 11.2.2b — Riser and going dimensions (mm) — stairways serving non-habitable rooms used infrequently]
[See Figure 11.2.2a — Measurement of slope relationship — Plan view — Stair with 2 flights]
[See Figure 11.2.2b — Measurement of slope relationship — Plan view — Tapered treads not more than 1 m wide]
[See Figure 11.2.2c — Measurement of slope relationship — Plan view — Tapered treads more than 1 m wide]
[See Figure 11.2.2d — Spiral stairs — Measurement for slope relationship]
[See Figure 11.2.2e — Spiral stairs — Measurement of openings in stairs]
[See Figure 11.2.2f — Riser and going dimensions — Measurement]
Explanatory information: 11.2.2(1)(a) states that a stairway must have not more than 18 and not less than 2 risers in each flight. Where there are less than 2 risers in a flight, it does not comprise a stairway for the purpose of the NCC. 18 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 1 riser is considered necessary for a person to observe and adjust to a change in level.
Explanatory information: The purpose of 11.2.2 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 11.2.2a and Table 11.2.2b express ratios between going and riser dimensions which are considered safe for use. 11.2.2(1)(c) 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. Explanatory Figure 11.2.2a 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. Explanatory Figure 11.2.2b 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 diagrams, the stairs in the flight are deemed constant. Irrespective of any minor deviations permitted by 11.2.2(1)(c), finished going and riser dimensions must not exceed the limitations stipulated in Table 11.2.2a. [See Figure 11.2.2a (explanatory) — Minor deviations in a stairway — deviation in adjacent risers] [See Figure 11.2.2b (explanatory) — Minor deviations in a stairway – deviations over a flight]
Explanatory information: 11.2.2(1)(d) allows the use of open riser stairs. However, it limits the openings to 125 mm to minimise the risk of a person (especially a young child) falling through the opening created by the open riser.
Explanatory information: 11.2.2(1)(e) specifies a height where solid treads must be used so that people cannot see through them. This minimises the risk of people being affected by vertigo.
Explanatory information: • 11.2.2(3) allows the use of winders in stairways. However, 11.2.2(3) places a restriction on the number of allowable winders in a stairway flight, this restriction would apply equally to not permit a stairway incorporating a consecutive series of winders in a flight. • This also means the maximum number of consecutive winders in any stairway flight is 6.
| Stair type | Riser (R) (see Figure 11.2.2f) | Going (G) (see Figure 11.2.2f) | Slope relationship (2R+G) | |||
|---|---|---|---|---|---|---|
| Max | Min | Max | Min | Max | Min | |
| Stairs (other than spiral) | 190 | 115 | 355 | 240 | 700 | 550 |
| Spiral | 220 | 140 | 370 | 210 | 680 | 590 |
Note: Riser and going dimensions must be measured in accordance with Figure 11.2.2f
| Riser (R) | Going (G) | Slope relationship (2R+G) | |||
|---|---|---|---|---|---|
| Max | Min | Max | Min | Max | Min |
| 225 | 130 | 355 | 215 | 700 | 540 |
Note: The going (G) must be not more than the tread depth plus a maximum gap of 30 mm between the rear edge of one tread and the nosing of the tread above.
Figures referenced (view on the ABCB site — images aren't reproduced here):
(1) A continuous barrier must be provided along the side of a trafficable surface, such as—
(a) a stairway, ramp or the like; and
(b) a floor, corridor, hallway, balcony, deck, verandah, mezzanine, access bridge or the like; and
(c) a roof top space or the like to which general access is provided; and
(d) 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 (see Figure 11.3.3a).
(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 (see Figure 11.3.3b); or
(b) a barrier provided to an openable window covered by 11.3.7 and 11.3.8; or
(c) a barrier complying with AS 1657 serving a fixed platform, walkway, stairway or ladder provided in accordance with 11.2.7(a).
[See Figure 11.3.3a — Barriers — when required]
[See Figure 11.3.3b — Barriers — when required for retaining walls]
Explanatory information: The intent of the barrier requirements is to prescribe provisions to minimise the risk of a person falling from a stairway, raised floor level (such as a balcony) or the like. 11.3.3 sets out when barriers are required to be provided and 11.3.4 contains the requirements for the construction of barriers.
Explanatory information: 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.
Figures referenced (view on the ABCB site — images aren't reproduced here):
(1) A barrier required by 11.3.3 must comply with (2) to (11).
(2) The height of a barrier must be in accordance with the following:
(a) The height must not be less than 865 mm above the nosings of the stair treads, the floor of a ramp or the like (see Figure 11.3.4a).
(b) 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 (see Figure 11.3.3b and Figure 11.3.4a); 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 (see Figure 11.3.4b).
(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 (see Figure 11.3.4a).
(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.
(7) A barrier to a stairway serving a non-habitable room, such as an attic, storeroom or the like that is not used on a regular or daily basis, need not comply with (4) if—
(a) openings are constructed so that they do not permit a 300 mm sphere to pass through; or
(b) where rails are used, the barrier consists of a top rail and an intermediate rail, with the openings between rails not more than 460 mm.
(8) Restriction on horizontal elements:
(a) 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.
(b) For the purpose of (a), the 4 m is measured from the floor level of the trafficable surface to the surface beneath.
(9) A barrier constructed of wire is deemed to meet the requirements of (4) if it is constructed in accordance with 11.3.6.
(10) A glass barrier or window serving as a barrier must comply with H1D8 and the relevant provisions of this Part.
(11) A barrier, except a window serving as a barrier, must be designed to take loading forces in accordance with AS/NZS 1170.1.
[See Figure 11.3.4a — Barrier construction]
[See Figure 11.3.4b — Measuring heights for barriers and handrails and where transition zones are allowed]
Explanatory information: For a window forming part of a barrier, any horizontal elements such as a window sill, transom or rail between 150 mm and 760 mm above the floor is deemed to facilitate climbing. Section 8 contains the glazing assembly provisions for glass barriers and windows forming part of the barrier, however, the barrier would still need to comply with the relevant requirements of this Part for required height, allowable openings, etc.
Figures referenced (view on the ABCB site — images aren't reproduced here):
(1) Compliance with Part 11.2 of the ABCB Housing Provisions satisfies Performance Requirement H5P1 for stairway and ramp construction.
Got a follow-up? StandAId answers questions on the text of the NCC 2025 — Volumes One, Two, Three and the Housing Provisions — with the clause linked. Free account, 3 questions a day; upload your own standards for more.
Ask the NCC in StandAId — free, 3 questions a dayWhere a person could fall 1 m or more from a trafficable surface — landings, decks, balconies, stairs — the Housing Provisions require a barrier. See 11.3.3.
The Housing Provisions set minimum barrier heights for landings/decks and for stairs, plus limits on openings and climbable elements. See 11.3.4 for the figures.
Risers and goings must be within the permitted ranges and consistent through a flight — see 11.2.2.
The National Construction Code 2025 was provided by the Australian Building Codes Board under the CC BY 4.0 licence. © Commonwealth of Australia and the States and Territories of Australia 2026, published by the Australian Building Codes Board. Licence: CC BY 4.0. NCC text on this page was extracted from the ABCB's NCC 2025 dataset (v1.2) and reformatted; figures, diagrams and photographs are not reproduced (they are outside the licence) — follow the links to view them on the ABCB site. The ABCB publishes the NCC without warranty and it is not legal or professional advice.
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