Granny Flats

A granny flat is a small, self-contained home that sits on the same property as a main house. It’s designed to complement the main dwelling.

Anyone can live in a granny flat – they don’t need to be related to the people in the main house.

Granny flats are referred to under the:

• Building Act: “Small Stand-alone Dwelling.”
• Resource Management Act: “Detached Minor Residential Unit.”

The name can change depending on the legislation, but both refer to the same type of building.

The building consent exemption is a result of changes under the Building and Construction (Small Stand-Alone Dwellings) Amendment Act 2025, while the recently introduced National Environmental Standard for Detached Minor Residential Unity (NES-DMRU) means that a resource consent may not be required.

Before you start building work

• You’ll still need to make sure your granny flat meets the Building Code, and that all the building work is done or supervised by a Licensed Building Practitioner (LBP). This means firstly, you’ll need to contact Hurunui District Council (HDC) and apply for a Project Information Memorandum (PIM) – this must be issued before any building work starts.
• HDC will review your project through the PIM process, including an assessment of whether it is likely to meet the provisions of the NES-DMRU.

You will receive advice on whether your project is:

• Likely to meet building exemption conditions
• Unlikely to meet building exemption conditions
• Uncertain

(Note - HDC does not check your plans to make sure they meet the Building Code.)

Effluent treatment systems: If an onsite effluent treatment system is proposed, Environment Canterbury rules also apply.

Some site conditions, like natural hazards, may still mean you need a building consent and/or resource consent.

If your project meets the Building Act exemption but requires resource consent, you can’t build until that resource consent is granted.

Exemptions

Your First Tool: Use the official Building Design Conditions Checklist to confirm your granny flat’s eligibility. The completed form must be supplied with your application

This is also very helpful: Granny Flats Exemption Guidance

Your granny flat must:

• Be a new, standalone (detached), single-storey (no mezzanine), and be self-contained. It must function as a complete dwelling (classified as ‘Housing – detached dwelling’ under the Building Code), intended for a single household or family.
• Have a floor area of 70 m² or less, (internal dimensions).
• Have a maximum floor level of 1 metre above the supporting ground and a maximum building height of 4 metres above the floor level.
• Be at least 2 metres from other residential buildings or legal boundaries and not built across allotment boundaries.
• Use lightweight materials:
• Roof cladding max 20kg/m².
• Wall cladding max 220kg/m².
• Light steel or timber framing.
• Connect to utilities (water, surface water, foul water) via network utility operators (e.g., council systems) where available, or use approved on-site systems if unavailable. Systems must follow specific compliance pathways (e.g. G12/AS1 for water supply, E1/AS1 for surface water).
• Meet additional plumbing criteria: Total fixture units ≤30, no pumped systems inside, specific drain sizes/grades, independent electricity/gas supplies, and no uncontrolled water heating.
• Showers must be prefabricated units (no level-entry/wet-floor showers).
• Cannot contain a woodburner.

Check all the criteria

• If your project qualifies for the building consent exemption, you must apply for a Project Information Memorandum (PIM) before starting any work and all exemption regulations.
• Please discuss with HDC if you are in a Natural Hazard Zone.
• Granny flats can be built off-site and moved onto your property, or built directly on your property.
• No more than 50% of the property in any Residential Zone (not applicable for a Rural Zone) can be covered with buildings.
• It must be set back no less than 2m from property boundaries in Residential Zones (unless there are reverse sensitivity issues to avoid).
• It must be set back no less than 10m from the front boundary and 5m from all other boundaries in Rural Zones (unless there are reverse sensitivity issues to avoid).
• Other approvals may be needed for network utility connections, vehicle crossings or land use restrictions.
• Development Contributions may apply.
• Construction of a minor residential unit will likely result in an increase in the rates you pay on your property. Please contact Rates for more information, 03 3148 816 or rates@hurunui.govt.nz

After the build

Let HDC know when the building work is finished and send us all required documents within 20 working days.

Within 20 working days of completing the work, the building owner must provide HDC with:

• Final Plans: Building and plumbing/drainage plans, including any changes made during construction
• Records of work from Licensed Building Practitioners: Certifications for services from the people who carried out the work – Plumbing, Drainage, Gas, Electrical.

The paperwork is an administrative step only. You must complete the building work within two years of the PIM issue date, unless you apply to HDC for an extension and it is approved.

This process creates a record of the work done on your property. It’s useful later if someone applies for a Land Information Memorandum (LIM).

HDC doesn’t inspect or certify Building Code compliance under the exemption, but has the usual powers to deal with any work that is unsafe or doesn’t comply with the rules.

What to do now?

Give HDC a ring, or pop in - have a chat with a Duty Planner or a Duty Building Officer to make sure you are able to have a granny flat on your property.

Call 03 0314 8816, or email info@hurunui.govt.nz

Apply for a PIM.

More information