It's one of the first questions on any home project, and getting it wrong is expensive. Unconsented work can hold up a future sale and cost far more to fix after the fact. The good news is the rule is clearer than most people expect.
The default is: yes
Under the Building Act, building work generally needs a building consent from your local council before it begins. Consent is the council checking your plans comply with the Building Code before a hammer swings. It isn't a formality to sort out later.
The exemptions
Schedule 1 of the Building Act exempts certain low-risk work, such as some decks and platforms under a set height, small sheds, and minor repairs or replacements using comparable materials. The limits are specific, though: height, floor area, and proximity to boundaries all matter, and getting the exemption wrong is on you.
Consent isn't the finish line
A consent lets you start; a Code Compliance Certificate confirms the finished work actually met the code. You want both. Skipping the CCC leaves a gap in the property's record that a buyer's lawyer will find.
When in doubt, ask first
Your council's building team will tell you whether your project needs consent, and a Licensed Building Practitioner or a designer can scope it properly before you commit. It's a short conversation that saves a long headache.
Find a licensed builder or a qualified designer for your region on The Contractor Hub.