The 1 in 8 figure is the most misquoted number in residential driveway design, read as a cap on grade change per metre. It isn't.
It's 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 at an eased grade between two steeper or flatter runs, spreading the slope change over enough distance for a vehicle to follow without touching.
So it has its own length and gradient. It isn't a difference between two numbers.
The Queensland rule, read carefully
Under QDC NMP 1.1, a driveway may reach 1 in 4 provided the run steeper than 1 in 5 stays within 6 metres. At each end of that 1:4 section, the change in gradient has to run at least 1 metre at no steeper than 1 in 8.
- 1 in 8 is the steepest the transition may be.
- 1 metre is the shortest it may run.
- 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, at 1 in 12 over a minimum length of one metre, in its driveway technical standards (checked 15 August 2026).
So the rate-of-change idea people attach to the state code does exist, in another document and at a stricter figure. In Brisbane, that's the number to design to. See driveway gradients in Brisbane.
Longer is better than minimum
A minimum-length transition satisfies the rule without guaranteeing a car will clear it.
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, running transitions longer than the minimum costs nothing on paper and removes the margin problem. More on the geometry 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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