What the QDC Actually Says About Driveway Gradients

The QDC is split into Mandatory Parts (MP) and Non-Mandatory Parts (NMP). Driveways sit in NMP 1.1, and the NMP prefix is meaningful: non-mandatory parts are those not referenced in legislation.

That does not make NMP 1.1 irrelevant. Councils reference it, development conditions invoke it, and certifiers use it as the yardstick when nothing more specific applies. But it is guidance rather than a statutory requirement in its own right, and a local planning scheme or an approval condition can and often does impose something different. Always check the conditions on the particular approval before assuming NMP 1.1 governs.

NMP 1.1 offers two acceptable solutions rather than one. The first is straightforward: a driveway with a maximum gradient of 1 in 5.

The second is the concession that matters on steep blocks. A driveway may reach a maximum gradient of 1 in 4, provided that the length steeper than 1 in 5 does not exceed 6 metres, and that there is a change in gradient not less than 1 metre in length and not greater than 1 in 8 at the ends of the 1:4 section.

Treating 1:8 as a general rate-of-change limit is conservative, so a profile drawn that way will usually satisfy NMP 1.1. The problem is the reverse case: a designer who believes the only requirement is 1:8 per metre may not realise that the 1:4 concession also caps the steep run at 6 metres, and requires a transition of at least a metre at both ends rather than one.

On a short, steep block those two extra conditions are frequently the binding ones. A 1:4 section of 7 metres does not comply no matter how gentle the transitions are, and a transition of 800 mm does not comply no matter how shallow its grade.

AS/NZS 2890.1 covers off-street parking and its residential access provisions are the other document a certifier is likely to have open. The two are not in conflict, but they are not identical either, and a driveway can be drawn to satisfy one while a condition on the approval requires the other.

In practice the safest position on a residential job is to know which document the approval actually cites, design to that, and keep the profile within the tighter of the two where they differ. A drawing that states its own gradients, transition lengths and RLs explicitly lets a reviewer confirm compliance against whichever document applies, without having to scale anything off the page.

NMP 1.1 also carries a performance requirement worth remembering: a vehicle should be able to travel the length of the driveway without scraping, scratching or being damaged.

That is the reason the transition rules exist. A grade change that satisfies every number on the page can still ground a long-overhang vehicle if the transition is short and the vehicle's departure angle is shallow. Numbers are the test a certifier applies; the vehicle is the test the client applies on the day they move in.

Whichever document governs, a driveway long section is easier to assess when it states its numbers explicitly rather than leaving them to be scaled off the page:

• The boundary RL and the finished garage slab RL
• Each zone's length, and its gradient expressed as a ratio
• The location and length of every transition
• The resulting platform level at the garage

DrivewayIQ holds every zone to the limits of the rule pack selected for the job and flags any rate of change worse than 1:8 over a metre as a warning, which is deliberately stricter than the NMP 1.1 transition clause. The intent is that a profile which passes has margin against either document rather than sitting exactly on a limit.