Statistics NZ publish a monthly series of building consents issued by every New Zealand local authority. That data includes categories for residential dwellings, from which this chart is derived.
Note that this series tracks the value of consents for new dwellings, and does not cover consents for only alterations of improvements to an existing residence. There are separate series for the number of consents issued, by region.
Also note that the issuing of a consent does not necessarily mean the project will be built. Some won't. New Zealand building consents usually require the project to start within 24 months, or the consent expires.