Building codes by country: the numbers a builder works to
Published · Updated · By Sai Nath
Each country sets its own stair and barrier numbers. A house stair riser can be up to 190 mm in Australia and on a main stair in New Zealand, 220 mm in England and 7¾ in (196 mm) in the US, and balustrade gaps must stop a 125 mm sphere in Australia, 100 mm in New Zealand and England, and 4 in in the US.
The main numbers, side by side
The figures for a stair and its balustrade in a house, from the document each country's builders work to. Each country page has the clause numbers, the conditions they apply to and the sources.
| Australia | New Zealand | England | United States | |
|---|---|---|---|---|
| Document | NCC 2025 Housing Provisions | D1/AS1 and F4/AS1 | Approved Document K (2013) | IRC (2021 and 2024) |
| Stair riser | 115 to 190 mm | 190 mm at most (main private stair) | 150 to 220 mm | 7¾ in (196 mm) at most |
| Stair going | 240 to 355 mm | 280 mm or more | 220 to 300 mm | 10 in (254 mm) or more |
| Other stair limit | 2R + G 550 to 700 mm | Pitch 37° at most | 2R + G 550 to 700 mm, pitch 42° at most | Risers within 3/8 in of each other |
| Headroom | 2.0 m | 2000 mm | 2.0 m | 6 ft 8 in (2032 mm) |
| Barrier needed where the fall is | 1 m or more | 1 m or more | more than 600 mm | more than 30 in (762 mm) |
| Barrier height on a stair | 865 mm | 900 mm | 900 mm | 34 in (864 mm) |
| Gap in a barrier must stop | a 125 mm sphere | a 100 mm sphere | a 100 mm sphere | a 4 in (102 mm) sphere |
Wales, Scotland and Northern Ireland have their own figures, and US states and cities adopt the IRC with their own amendments: the UK and US pages explain how. In every country the plans, the council or building department and the certifier or inspector decide what a job needs.
One stair, four countries
The same 2700 mm floor-to-floor height, with the fewest risers each country's maximum allows:
- Australia and New Zealand, 190 mm: 2700 ÷ 190 = 14.2, so 15 risers of 2700 ÷ 15 = 180 mm.
- England, 220 mm: 2700 ÷ 220 = 12.3, so 13 risers of 2700 ÷ 13 = 207.7 mm.
- United States, 196 mm (7¾ in): 2700 ÷ 196 = 13.8, so 14 risers of 2700 ÷ 14 = 192.9 mm, about 7 19/32 in.
The going then has to suit each riser. In England the 42° pitch limit needs a going of at least 207.7 ÷ tan 42° = 230.7 mm, so the 220 mm minimum is not enough on its own; a 235 mm going gives 2 × 207.7 + 235 = 650.4 mm, inside 550 to 700. New Zealand's 280 mm minimum makes its flight 14 × 280 = 3920 mm long, against 14 × 240 = 3360 mm in Australia. In the free Stairs calculator in MeisterCalc, type your country's maximum into Desired Riser Height and tick Riser Limited to get the same counts; the web stair calculator checks all four countries.
Rules country by country
- Australia: the NCC 2025 Housing Provisions
- New Zealand: the Building Code and its Acceptable Solutions
- United Kingdom: the Building Regulations and Approved Documents
- United States: the International Residential Code
Sources
Checked on 2 November 2026. These pages explain the rules; the code itself, your plans and your council, building consent authority, building control body or certifier decide what a job needs.
- NCC 2025 Housing Provisions, Part 11.2 Stairway and ramp construction: Table 11.2.2a (checked 1 November 2026)
- NCC 2025 Housing Provisions, Part 11.3 Barriers and handrails: 11.3.3(1), 11.3.4(2) and (4) (checked 1 November 2026)
- MBIE, D1/AS1 Access routes, 2nd edition, amendment 6: Table 6; current version, effective 1 January 2017 (checked 2 November 2026)
- MBIE, F4/AS1 Safety from falling, 3rd edition, amendment 2: Table 1; current version, effective 1 January 2017 (checked 2 November 2026)
- Approved Document K, 2013 edition, on GOV.UK: Table 1.1, 1.11, Diagram 3.1; for use in England (checked 1 November 2026)
- 2021 IRC, Chapter 3 Building Planning (ICC): R311.7 stairways, R312 guards (R318.7 and R321 in the 2024 IRC) (checked 1 November 2026)
Do the maths in MeisterCalc
MeisterCalc does the arithmetic behind these rules on an Android phone, with no signal needed: Stairs, Concrete and Check Square are free, and the other calculators come with Pro. It runs on Android 7.0 or later.