How does the NZ Building Code work, and what numbers does it set?
Published · Updated · By Sai Nath
New Zealand’s Building Code is Schedule 1 of the Building Regulations 1992. Its clauses say what a building must do, and MBIE’s Acceptable Solutions give one way to comply: D1/AS1 allows main private stair risers up to 190 mm with goings of 280 mm or more, F4/AS1 sets 1000 mm deck barriers, and E2/AS1 sets 8° for corrugated roofing.
How does the Building Code work?
The Building Act 2004 sets up the system, and the Building Code itself is Schedule 1 of the Building Regulations 1992. It is a performance code: each clause says what a building has to achieve, not how to build it. The clauses are grouped by letter: A General provisions, B Stability, C Protection from fire, D Access, E Moisture, F Safety of users, G Services and facilities, and H Energy efficiency. A house or deck job mostly involves B1 Structure, D1 Access routes, E1 Surface water, E2 External moisture and F4 Safety from falling.
The numbers are in the Acceptable Solutions and Verification Methods, which MBIE issues under section 22 of the Building Act. Build to one and the work is treated as complying with that clause. They are not the only way: section 19 of the Act lists other routes, and a design can show it meets the clause another way, as an alternative solution. Your building consent authority, usually the council, decides what it accepts, and the consented plans beat any figure here.
Which documents does a house job use?
Each Acceptable Solution has editions and amendments, and building.govt.nz lists the current one on the clause’s page. These were the current versions on 1 November 2026:
| Clause | Acceptable Solution | In force from | What it covers here |
|---|---|---|---|
| B1 Structure | B1/AS1, 2nd edition, which cites NZS 3604:2011 with changes | 28 July 2025 | Footings and piles |
| D1 Access routes | D1/AS1, 2nd edition, amendment 6 | 1 January 2017 | Stairs, landings, handrails |
| E2 External moisture | E2/AS1, 4th edition | 28 July 2025 | Roof pitch by cladding |
| F4 Safety from falling | F4/AS1, 3rd edition, amendment 2 | 1 January 2017 | Barrier heights, baluster gaps |
A new edition runs alongside the old one for a while: the previous B1/AS1 and E2/AS1 could be used for consent applications made before 1 August 2026. The 2025 editions renumbered their paragraphs and tables, so an older detail sheet may cite a number that has moved.
NZS 3604:2011 Timber-framed buildings, which B1/AS1 cites with modifications, has been free to download since 2019. A revised draft was out for comment from 29 June to 22 September 2026; Standards New Zealand says the draft must not be used for building, so the 2011 edition still applies.
The numbers chippies use most
| What | Figure | Where | Guide |
|---|---|---|---|
| Main private stair | Riser 190 mm or less, going 280 mm or more, pitch 37° or less | D1/AS1 Table 6 | NZ stairs |
| Secondary private stair (bedrooms and bathrooms only) | Riser 200 mm, going 250 mm, pitch 41° | D1/AS1 Table 6 | NZ stairs |
| Headroom over a stair | 2000 mm above the pitch line | D1/AS1 Table 1, Figure 3 | NZ stairs |
| Handrail height | 900 to 1000 mm above the pitch line | D1/AS1 6.0.6 | NZ stairs |
| When a barrier is needed | A possible fall of 1 m or more | Building Code F4.3.1 | Baluster gaps |
| Barrier height, house | 900 mm on stairs, 1000 mm on decks and balconies | F4/AS1 Table 1 | Baluster gaps |
| Openings in a barrier, house | Must stop a 100 mm sphere | F4/AS1 1.2.1 | Baluster gaps |
| Corrugated metal roof | 8° or steeper | E2/AS1 8.4.4.1 | Roof pitch |
| Butyl or EPDM membrane | 2° on a roof, 1.5° on a deck | E2/AS1 8.5.1.2 | Roof pitch |
| Good ground | 300 kPa ultimate bearing (100 kPa allowable) | B1/AS1 1.2.1.1 | Footings |
| Ordinary timber pile footing | 200 mm deep, with the pile 100 mm into it | NZS 3604, as BRANZ Bulletin 560 explains | Footings |
Worked example: a deck 1.2 m up, with steps
A house deck 1200 mm above the lawn, with steps down to it.
- Barrier: a fall of 1200 mm is more than 1 m, so the deck needs a barrier (F4.3.1). On a house deck it is 1000 mm high (F4/AS1 Table 1), with no opening that lets a 100 mm sphere through.
- Stair type: D1/AS1 counts every exterior private stair as a main private stairway, so the steps use 190 mm, 280 mm and 37°.
- Risers: 1200 ÷ 190 = 6.3, rounded up to 7 risers of 1200 ÷ 7 = 171.4 mm.
- Goings: 7 − 1 = 6 treads of 280 mm, 6 × 280 = 1680 mm of going.
- Pitch: arctan(171.4 ÷ 280) = 31.5°, under 37°.
- Handrail: with 7 risers the steps need a handrail on at least one side, 900 to 1000 mm above the pitch line (D1/AS1 6.0.1 and 6.0.6). Where the side of the flight is 1 m or more above the ground, its barrier is 900 mm above the pitch line.
Which MeisterCalc calculators help?
The app has no New Zealand presets: you type in the figure from the Acceptable Solution. Stairs warns with Australian figures (a riser over 190 mm or under 115 mm), so for a NZ stair set Desired Riser Height to the Table 6 maximum, tick Riser Limited and type a going of 280 mm or more. Baluster Spacing starts its Max Spacing at 125 mm, the Australian figure: set it to 100. Pitch turns a rise and run into degrees for the roof minimums, and Concrete adds up pile footings in its Holes mode. Stairs, Concrete and Check Square are free; the rest come with Pro. Framing spacings and other NZ sums are in construction calculations for New Zealand.
The app and this page don’t make work comply. Where something varies, such as the wind zone, the ground or a council’s own requirements, check with your building consent authority.
New Zealand rules, topic by topic
- What are the D1/AS1 stair rules for a house in New Zealand?
- What is the minimum roof pitch in NZ for each roof cladding?
- How deep and how big are pile footings under NZS 3604?
Sources
Checked on 1 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.
- MBIE, E2/AS1 External moisture, 4th edition (PDF): preface: the Building Code is Schedule 1 of the Building Regulations 1992, acceptable solutions issued under section 22, other routes in section 19; effective 28 July 2025, 3rd edition usable for applications before 1 August 2026; 8.4.4.1, 8.5.1.2 (checked 1 November 2026)
- MBIE, E2 Acceptable Solutions and Verification Methods: lists E2/AS1 4th edition, effective 28 July 2025, as the current version (checked 1 November 2026)
- MBIE, D1 Acceptable Solutions and Verification Methods: D1/AS1 2nd edition, amendment 6, effective 1 January 2017, current; the PDF gives Table 6, Table 1, Figure 3, 6.0.1, 6.0.6 and the stair definitions (checked 1 November 2026)
- MBIE, F4 Acceptable Solutions and Verification Methods: F4/AS1 3rd edition, amendment 2, effective 1 January 2017, current; the PDF gives clause F4.3.1, Table 1 and 1.2.1 (checked 1 November 2026)
- MBIE, B1/AS1 Structure, 2nd edition (PDF): effective 28 July 2025; 1.2.1.1 good ground; 2.3 modifications to NZS 3604:2011; 1st edition usable for applications before 1 August 2026 (checked 1 November 2026)
- MBIE, Using NZS 3604 Timber-framed buildings: NZS 3604 is cited by B1/AS1 with modifications and has been free to download since 2019 (page last updated 26 January 2026) (checked 1 November 2026)
- Standards New Zealand, DZ NZS 3604 Timber-framed buildings consultation: draft revision open for comment 29 June to 22 September 2026; the draft is not to be used for building (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.