Planning rules in Northern Territory

Up to 75 m² of floor area in certain zones (increased from 50 m² on 1 December 2023), including any carport or veranda, on the same lot as the main house.

Only in the right zone. Most established Darwin suburbs are Zone LR (Low Density Residential), where the scheme allows one dwelling-single per lot plus one dwelling-independent of up to 75 m² - a granny flat rather than a true duplex. A dwelling-group of fewer than five dwellings is a permitted use in Zone LR, but you would need the consent authority to vary the density limit to build two full dwellings. In Zone LMR the density is set per dwelling - 150 m² for a 1 bedroom and 300 m² for a 2+ bedroom dwelling - which is where two separate dwellings genuinely work.

You need a development permit unless the proposal is exempt, and the land has to meet the minimum lot size and configuration requirements for your zone under the NT Planning Scheme 2020. Zone LR (Low Density Residential) indicatively works to about 800 m² per lot, the medium and high density residential zones allow smaller lots, and rural residential and rural zones are measured in hectares - so the answer turns on your zone rather than a single territory-wide number.

Yes. Darwin is a building control area, so a deck or verandah is structural work that needs a building permit and certification from an NT-registered building certifier.

A small freestanding storage shed with a roof area under 15 m², floor area under 30 m², under 2.5 m high and with no services can be built without a building permit in a residential area. Larger sheds need a permit inside building control areas.

The NT does not set a single published height limit for domestic fences. The practical test is structural - a fence that must resist cyclonic wind loading generally needs building certification, so confirm your design with NT Building Advisory Services or a registered certifier.