Granny-flat rules have changed: check the services before choosing a plan

What the October amendments cover

MBIE identifies two changes. Certified composite structural products, including some structural insulated panel and solid-timber systems, can now qualify. Use must stay within the registered CodeMark certificate's scope and limitations and follow the manufacturer's instructions.

Existing network connections may be used or modified where the utility provider agrees they are suitable; its required approvals still apply. Existing on-site water and drainage systems may also be used or upgraded if they have adequate capacity and comply with the Building Code.

These are targeted amendments to an existing exemption. They do not establish that a particular building system or connection suits your project.

Put the service question on the first sketch

I would ask for the proposed water supply, wastewater and stormwater arrangements to be shown alongside the building position. A floor plan on its own does not tell me whether the proposal has been thought through as a whole.

For a hypothetical family considering a second home behind their existing house, I would want the team to explain which services they intend to share, which need further investigation and who will confirm the answer. That makes the discussion much more useful than simply asking whether there is room for the building.

• What evidence do we have about the existing services?
• Who will confirm suitability and any required approvals?
• Would a different building position be worth testing before we settle the layout?

Keep the wider exemption checks visible

MBIE's homeowner guidance describes eligible dwellings as new, standalone, single-storey and no more than 70 square metres, with all exemption conditions satisfied. Building Code compliance and licensed professional involvement remain necessary.

You must obtain the granny-flat project information memorandum, or PIM, before starting work. It provides information, rather than approval. Planning requirements, covenants, bylaws and natural hazards still need checking. Councils do not inspect exempt work or issue a code compliance certificate for it.

I would ask the team to explain the proposed checking and record-keeping arrangements before choosing this route. MBIE also advises speaking to lenders and insurers early about the evidence they need. An exemption should be a considered project decision.

Give both homes a proper place on the section

My design priority would be making the additional dwelling feel like a home in its own right. Where do visitors arrive? Can someone sit outside without feeling they are in the other household's way? What happens when both households have washing out, visitors over or shopping to carry?

Try drawing the everyday routes for each household over the same site sketch. Mark the places where they cross and talk through whether that feels comfortable. I would use that exercise to test the preferred position before becoming attached to the internal plan.

The October changes give the team specific technical questions to revisit. I would still judge the resulting design by how well it supports the people living there.

Bring the whole property into the conversation

If you have an earlier concept, ask what assumption the new rules might change and what evidence is needed to confirm it. Keep the answer specific to the proposal.

Bring your address, any site or drainage plans and a short description of who the additional home is for to a conversation with Modal Architecture. We can discuss the investigations and design work that would help you decide whether to take it further.