The 1 in 8 figure is the most misquoted number in residential driveway design. It is usually described as a limit on how much the grade may change over any metre of driveway. That is not what it says.
It is the steepness of the transition at each end of a steep section — and that transition has a minimum length.
What a transition actually is
A transition is a short section of driveway at a deliberately eased grade, sitting between two steeper or flatter runs. Its job is to spread a change in slope over enough distance that a vehicle can follow it without touching.
It is a piece of the driveway with its own length and its own gradient — not a mathematical difference between two other numbers.
The Queensland rule, read carefully
Under QDC NMP 1.1, a driveway may reach 1 in 4 provided the length steeper than 1 in 5 does not exceed 6 metres, and there is a change in gradient of at least 1 metre in length and no steeper than 1 in 8 at the ends of the 1:4 section.
- 1 in 8 is how steep the transition may be — no steeper.
- 1 metre is how long it must run — no shorter.
- Each end. Both ends of the steep section, not one.
Some councils use a different test entirely
Brisbane City Council does limit rate of change — to 1 in 12 over a minimum length of one metre, per its published driveway technical standards (checked 15 August 2026).
So the rate-of-change idea people attach to the state code does exist — just at a different figure, in a different document, and it is stricter. If your job is in Brisbane, that is the number to design to. See driveway gradients in Brisbane.
Longer is better than minimum
A minimum-length transition satisfies the rule. It does not necessarily satisfy the vehicle.
NMP 1.1's performance requirement is that a vehicle can travel the driveway without scraping, scratching or being damaged. A car with a long front overhang and low clearance can ground on a transition that meets every published figure.
Where the site allows it, running transitions longer than the minimum costs nothing on paper and removes the margin problem entirely. Why the geometry behaves this way is covered in rate of grade change, and the vehicle side in why your car scrapes.
Disclaimer
General information, not advice. This summarises QDC NMP 1.1 as published rather than reproducing it, and Brisbane City Council's published standards as at 15 August 2026. NMP 1.1 is a non-mandatory part of the Queensland Development Code, and councils and individual approvals may require something different. Confirm with the relevant council or a qualified certifier.
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