Many Hamilton homeowners confuse resource consent with building consent. They're two completely different approvals, administered by different teams, covering different things.
Resource Consent
Resource consent is about land use - whether you're allowed to use your land in a particular way under the Hamilton District Plan. It's granted by Hamilton City Council's planning team.
Building Consent
Building consent is about how something is built - whether the structure meets the requirements of the New Zealand Building Code. It's granted by the building team.
Do You Need Both?
Often, yes. A granny flat might need resource consent (for land use) and building consent (for the construction). In some cases you might need one but not the other.
Rule of thumb: Resource consent = permission to do it. Building consent = permission to build it the way you've described. Get professional advice to understand which applies to your project.
Which Comes First?
Resource consent first, then building consent. There's no point getting building consent plans drawn up if resource consent is refused. Sort out your planning approvals before investing heavily in detailed building design.