What is the maximum riser height for stairs in Australia?

For private stairs (in Class 1 and 10 buildings), the NCC Housing Provisions say each step can be no taller than 190 mm — the long-standing figure. Any taller and the step is too big to climb safely, so 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.

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.

In this section

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

The rule, in one line

A stair needs to be steep enough to fit the space, but shallow enough to climb safely. The NCC sets this with three numbers — the riser, the going, and a formula that links them. They sit in the Housing Provisions (NCC 2025, clause 11.2).

Riser (R) — how tall each step is.
Going (G) — how deep each step is, measured 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.

Dimension	Limit (NCC 2025)
Riser (R)	max 190 mm · min 115 mm
Going (G)	max 355 mm · min 240 mm
2R + G	between 550 mm and 700 mm
Risers per flight	max 18 before a landing

NCC 2025 Housing Provisions 11.2

1 nosing

Every step in a flight must be the same height, and every step must be the same depth. The NCC only lets them vary by a tiny bit — because 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.

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.
Pick a step depth. Try a going of 250 mm.
Do the 2R+G check. (2 × 184) + 250 = 618 mm. That’s inside the 550–700 range — comfortable.

If 2R+G came out under 550, the stair would feel cramped. Over 700, and it’d be a stretch to walk. Change the going (or the number of steps) until it lands in range.

Do it in 5 seconds

Sources

NCC 2025, ABCB Housing Provisions Standard, clause 11.2 — stairways (riser, going, 2R+G, slope relationship). Confirm each figure at ncc.abcb.gov.au. (Confirmed against the NCC 2025 Housing Provisions Standard, verified 2026-07-28.)

More Australia rules

Frequently asked questions

What is the maximum riser height for stairs in Australia?: For private stairs (in Class 1 and 10 buildings), the NCC Housing Provisions say each step can be no taller than 190 mm — the long-standing figure. Any taller and the step is too big to climb safely, so 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.