# NZ Stair & Barrier Rules: Riser, Tread, Handrails, Barriers

The NZ Building Code numbers for a main house stair — 190 mm max riser, 280 mm min tread, 900/1000 mm barriers — from the D1/AS1 and F4/AS1 Acceptable Solutions.

- Canonical HTML: https://www.chippy.tools/building-codes/nz/stairs/stair-and-barrier-requirements/
- Publisher: Chippy Tools
- Updated: 2026-09-06
- Market: nz
- Code edition / reference: NZBC D1/AS1 & F4/AS1
- References: NZ D1; F4


## The requirement

For the main stair in a house, each riser can be no more than **190 mm** tall. Each going must be at least **280 mm** deep. Keep every riser in the flight the same height. Main private stairs also have a **37° maximum pitch** in Table 6. The numbers come from **D1/AS1**, the deemed-to-comply Acceptable Solution under the NZ Building Code.

The riser is how tall each step is. D1/AS1 calls its 280 mm limit tread depth. Use its Figure 12 to measure that depth and any nosing. Do not confuse it with the timber board width. A stair has to be steep enough to fit the space. It also has to be shallow enough to climb safely. Secondary and service stairs are allowed to be a bit steeper. The table shows all three.

| Dimension   | Main house stair | Secondary | Service / minor |
|-------------|------------------|-----------|-----------------|
| Riser (max) | **190 mm**       | 200 mm    | 220 mm          |
| Going (min) | **280 mm**       | 250 mm    | 220 mm          |

Two more numbers finish the stair off:

- Headroom: at least **2100 mm** clear above the stair. You can drop to **2000 mm** over a short landing, or a stair or corridor under 2 m long.
- Handrail: set it **900–1000 mm** above the pitch line. The pitch line runs up the front edges of the steps.
- Width: the Acceptable Solution does not fix a minimum width for a stair inside a house. Set it to suit the space. The 900 mm figure is for common or accessible stairs, not a private home stair.

**Diagram labels:** ≤ 190 mm; ≥ 280 mm

NZBC D1/AS1 · main private stair

## Guards & barriers

A barrier stops people falling off an edge. Under **F4/AS1** you need a barrier anywhere a person could fall **1 m or more**. The height depends on where it is.

| Where                                     | Barrier height                       |
|-------------------------------------------|--------------------------------------|
| Stairs, ramps and their landings          | **900 mm**                           |
| Balconies, decks and internal floor edges | **1000 mm**                          |
| Trigger — barrier required                | wherever the fall is **1 m or more** |

The gaps in a barrier matter too. A small child must not slip through:

- On a house barrier, a **100 mm** sphere must not pass through any gap. In housing the Code always treats the building as used by children under 6.
- In the triangle formed by a stair’s riser, tread and rail, a **150 mm** sphere must not pass.

## Work it out on site

Say your floor-to-floor height is **2800 mm**. You want an even, comfortable main stair.

1. **Pick how many risers.** 2800 ÷ 190 (the tallest a riser can be) = 14.7. You can’t have part of a step, so round up to 15 risers. 2800 ÷ 15 = **186.67 mm** per riser (rounded for display). That is under the riser limit, but does not prove the whole stair complies.
2. **Set the going.** Try **280 mm**, the minimum for a main stair. Fifteen risers means 14 goings. So the stair runs 14 × 280 = 3920 mm along the floor. Check it fits the space you have.
3. **Check the space before changing the count.** At the same 280 mm going, 16 risers would need 15 goings and **4200 mm** of run. Adding a riser lowers the rise but makes this straight flight longer. If 3920 mm does not fit, redesign the layout with the required landings and clearances. Keep every riser equal and recheck all applicable limits.

The calculator does this rounding for you and keeps the risers even.

## Do it in 5 seconds

## Related

- [New Zealand Building Code hub](https://www.chippy.tools/building-codes/nz/): how the one national Code and its Acceptable Solutions work.
- [NCC stair requirements (Australia)](https://www.chippy.tools/building-codes/au/stairs/ncc-stair-requirements/): the Australian numbers, for anyone comparing across the ditch.

## Sources

- **NZBC D1/AS1 — Access routes**, Table 6 (riser and tread), clause 1.4 (headroom) and clause 6.0.6 (handrail height). [Official D1 PDF](https://www.building.govt.nz/assets/Uploads/building-code-compliance/d-access/d1-access-routes/asvm/d1-access-routes-2nd-edition-amendment6.pdf).
- **NZBC F4/AS1 — Safety from falling**, Table 1 (barrier heights and the 1 m fall trigger) and clause 1.2.1 (barrier openings). Confirm each figure and the current amendment in the [official F4 PDF](https://www.building.govt.nz/assets/Uploads/building-code-compliance/f-safety-of-users/f4-safety-from-falling/asvm/f4-safety-from-falling-3rd-edition-amendment2.pdf).

**Read this first.** New Zealand has one national Building Code, so these rules apply the same everywhere. But the numbers above are the **Acceptable Solution** (deemed-to-comply) path. A designer may propose an **Alternative Solution**, which can carry different numbers — so treat these as the standard path, not the only legal one. Always re-check the current amendment on building.govt.nz before you sign off.


Sourced from the New Zealand Building Code, © Crown copyright, reused under NZGOAL / Creative Commons Attribution.

This page is general information for tradespeople and is not compliance, engineering or legal advice. Requirements are subject to state and territory variations and adoption timing. Always confirm requirements with your building certifier and relevant state authority.


## Frequently asked questions

### What is the maximum riser height for a house stair in New Zealand?

For the main stair in a house, the D1/AS1 Acceptable Solution sets each riser (step height) at no more than 190 mm. A secondary stair can go to 200 mm, and a minor service stair to 220 mm. Every riser in a flight should be the same height so the stair is safe to climb.

### What is the minimum tread depth for a NZ stair?

For the main house stair the tread (the flat part you stand on) must be at least 280 mm deep under D1/AS1. A secondary stair can drop to 250 mm and a service stair to 220 mm. Deeper treads pair with lower risers to make a comfortable stair.

### How high should a barrier be on a NZ deck or stair?

Under F4/AS1 a barrier is 900 mm high on stairs, ramps and their landings, and 1000 mm at balconies, decks and internal floor edges. You need a barrier anywhere a person could fall 1 m or more.

### How wide should a house stair be in New Zealand?

The Acceptable Solution does not fix a minimum width for a stair inside a house. The 900 mm figure you may have heard is for common or accessible stairs, not a private home stair. Set the width to suit the space and the job. Then check the current amendment on building.govt.nz.

### Do these numbers apply everywhere in New Zealand?

Yes. New Zealand has one national Building Code, so every council uses the same rules. But these figures are the Acceptable Solution, the deemed-to-comply path. A designer can propose an Alternative Solution instead. Those can carry different numbers.