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NCC Stair Requirements: Riser, Going & the 2R+G Rule Explained

The NCC 2025 rules for private stairs — maximum riser, minimum going, and the 2R+G comfort formula — explained in plain English, with a worked example.

NCC 2025 Clause HP 11.2

Scope: Australia; Class 1 and 10 Housing Provisions. Confirm local adoption and variations.

Source text checked

Official source cross-check; not a site-specific compliance assessment.

The rule, in one line

For private stairs, each riser can be 190 mm tall at most. Each going must be at least 240 mm deep. And two risers plus one going must land between 550 and 700 mm. The rules sit in the Housing Provisions (NCC 2025, clause 11.2).

A stair needs to be steep enough to fit the space. It also needs to be shallow enough to climb safely. Three numbers keep it that way.

  • Riser (R): how tall each step is.
  • Going (G): how deep each step is. Measure from the front edge of one step to the front edge of the next.
  • 2R+G: a comfort check. Two risers plus one going must land inside a set range.
DimensionLimit (NCC 2025)
Riser (R)max 190 mm · min 115 mm
Going (G)max 355 mm · min 240 mm
2R + Gbetween 550 mm and 700 mm
Risers per flightmax 18 before a landing
1R ≤ 190 mmG ≥ 240 mmRRG++550 ≤ 2R + G ≤ 700 mm
NCC 2025 Housing Provisions 11.2
  1. 1 nosing

Every step in a flight must be the same height. Every step must be the same depth too. The NCC only lets them vary by a tiny bit. One odd step is where people trip.

How to work it out by hand

Say your floor-to-floor height is 2760 mm and you want to check a stair.

  1. Pick how many steps. 2760 ÷ 190 (the tallest a riser can be) = 14.5. You can’t have half a step, so you need at least 15 risers. 2760 ÷ 15 = 184 mm per step. That’s under the 190 limit. Good.
  2. Pick a step depth. Try a going of 250 mm.
  3. Do the 2R+G check. (2 × 184) + 250 = 618 mm. That’s inside the 550–700 range. This checks that formula.

If 2R+G comes out under 550, the stair feels cramped. Over 700, it’s a stretch to walk. Change the going, or the number of steps, until it lands in range.

Calculate and keep your working

Download the Chippy Tools stair set-out worksheet to record your inputs and the approved requirements.

Sources

  • NCC 2025, ABCB Housing Provisions Standard, clause 11.2 — stairways (riser, going, 2R+G, slope relationship). Confirm each figure at the official NCC provision. (Confirmed against the NCC 2025 Housing Provisions Standard, source text checked 2026-09-06.)

Related building rules

Content adapted from the National Construction Code 2022, provided by the Australian Building Codes Board under the CC BY 4.0 licence.

Frequently asked questions

What is the maximum riser height for stairs in Australia?
For private stairs (Class 1 and 10 buildings), the NCC Housing Provisions cap each riser at 190 mm. Any taller and the step is too big to climb safely. You add another step to bring each one down. Every step in a flight must also be the same height, give or take a tiny bit.
What does the 2R+G rule mean?
It's a comfort check. Two step heights plus one step depth must add up to a number inside a set range. It stops a stair from being too steep, or too stretched out, to climb safely.
Do all the steps in a flight have to be the same size?
Yes. Every step must be the same height, and every step must be the same depth. The NCC only lets them vary by a tiny bit, because uneven steps are easy to trip on.
Does this apply to deck and external stairs too?
Yes. The same riser, going and 2R+G numbers apply to outdoor and deck stairs. Outside stairs need a few extra things the numbers don't cover, like grippy treads and a barrier on any open edge. But the main numbers are the same as an indoor stair.