Ramp Gradients (NCC 2025): Houses vs Access Ramps

The requirement

For a normal Class 1a house, the step-free path in can be 1:14 at the steepest, measured the way you walk. Crossfall, the sideways slope, can be no steeper than 1:40. Those numbers come from Livable Housing Design (Volume Two, H8), not from the D4 ramp clause.

Most people quote the wrong rule here. The famous NCC ramp clause is Volume One D4D12. It points to the standard AS 1428.1 for the detail. But D4D12 only covers Class 2–9 buildings. That means units, shops, offices and the like. It does not cover a normal Class 1a house.

One more check before you build. How much of Livable Housing you must follow depends on your state or territory. They do not all adopt it the same way. So check your local rules first.

Here’s the split in plain terms:

Your job	Which rule	Gradient
A normal house (Class 1a)	Livable Housing Design (Vol Two H8)	1:14 max in the direction of travel
Units, shops, offices (Class 2–9)	Vol One D4D12 → AS 1428.1	per AS 1428.1 — don’t guess a number

The step ramp (Class 1a)

On the house path you also get one optional step ramp. That is a short, steeper ramp at a single step. It can be up to 1:10. Its rise can be up to 190 mm. Its length can be up to 1900 mm, and its width must be at least 1000 mm.

Walkway or ramp?

The slope decides what you are building. A slope of 1:20 or flatter is a walkway, which is just a path. No ramp landing or handrail rules apply to a walkway. Steeper than 1:20 and up to 1:14 is a ramp.

How far you can run before a break depends on the slope. You can run up to 9 m of ramp at 1:14. At 1:20 you can run up to 15 m. For a slope in between, the run limit sits in between too.

Landings

The flat bit at each end of the ramp is the landing. On a house access path each landing must be:

at least 1200 mm long,
at least as wide as the ramp, and
level, or up to 1:40 if you need a small fall to shed water.

NCC 2025 Livable Housing Design · AS 1428.1

For units, shops and offices (Class 2–9)

Is your job a Class 2–9 building? Then the ramp gradient comes from AS 1428.1, not from a number you pick. The detailed landing sizes and spacing come from that standard too.

D4D12 also sets two hard limits for these buildings:

A run of connected ramps must not climb more than 3.6 m in total.
One step-ramp landing must not overlap another.

Worked example

You are building the step-free path into a house. The front door sits 500 mm above the finished ground. How long does the ramp need to be at 1:14?

Pick the slope. A house access path can be 1:14 at the steepest. That means for every 1 unit up, you travel 14 along.
Do the sum. 500 mm up × 14 = 7000 mm, so 7 m of ramp run. This 7 m is just the maths of the example, not a code figure.
Check the run limit. You can run up to 9 m at 1:14. Your 7 m is under that, so a single run works. No mid-ramp landing is needed for length.
Add the landings. A level landing at least 1200 mm long goes at the top and the bottom.

So: about 7 m of ramp at 1:14, with a 1200 mm landing at each end. The slope calculator does this rise-over-run sum for you.

Do it in 5 seconds

Part of the NCC rules for Australian chippies — the pillar, with the state-by-state adoption tracker.
Building the stairs that ramp might replace? See NCC stair winders & landings.
Working out how high the barrier alongside it has to be? Balustrade height requirements.

Sources

NCC 2025, Volume Two, Livable Housing Design, Part 1 — Dwelling access — the Class 1a house access path (1:14 gradient, 1:40 crossfall, the 1:10 step ramp, the 1:20 walkway line, run lengths, and 1200 mm landings). Confirm at ncc.abcb.gov.au. (How much of Livable Housing applies depends on your state or territory — check your local adoption.)
NCC 2025, Volume One, Part D4 — Access for people with a disability, clause D4D12 (Ramps) — for Class 2–9 buildings: the 3.6 m combined-rise limit and the no-overlapping-landing rule. Confirm at ncc.abcb.gov.au.
AS 1428.1 (Design for access and mobility) — for Class 2–9 access ramps, the ramp gradient and the detailed landing sizes and spacing come from this standard. It is not free to read; check the figures in AS 1428.1 itself, or with your engineer, before you build.

Frequently asked questions

What ramp gradient does the NCC allow for a house?

For a normal Class 1a house, the step-free path in has a maximum slope of 1:14 in the direction you walk, with crossfall no steeper than 1:40. That comes from the Livable Housing rules, not the D4 ramp clause. The D4 ramp clause is for units, shops and offices.

Isn't D4D12 the ramp rule I should follow?

Only if you're building a Class 2–9 building — units, shops, offices and the like. D4D12 points to AS 1428.1 for the actual gradient. A normal house isn't covered by D4D12 at all. A house follows the Livable Housing access path instead, and how much of that applies depends on your state or territory.

When is it a walkway and when is it a ramp?

A slope of 1:20 or flatter is a walkway — no ramp landing or handrail rules kick in. Steeper than 1:20 and up to 1:14 is a ramp. You can run up to 9 m of ramp at 1:14, or up to 15 m at 1:20, and interpolate for slopes in between.

How big do the landings have to be?

On a house access path the landing at each end must be at least 1200 mm long, at least as wide as the ramp, and level — or up to 1:40 if you need a little fall to shed water.

Can I put a small step ramp in?

On a house access path you get one optional step ramp at up to 1:10. Its rise can be up to 190 mm, its length up to 1900 mm, and its width at least 1000 mm. For a Class 2–9 building, the ramp figures come from AS 1428.1, not from a number you pick yourself.