Granny flats building consent exemption will change on October 8, 2026, according to the Ministry of Business Innovation and Employment. The update widens the list of approved building products and makes it easier to use the water, wastewater and stormwater services that already serve the site, removing the need for new connections in many cases.
Under the new rule, certified composite structural products may be used for new accessory dwellings. This includes certain Structural Insulated Panel (SIP) systems and solid timber assemblies, as long as each product stays within the limits of its CodeMark certificate and the manufacturer’s instructions are followed to satisfy the Building Code.
The shift supports contemporary construction approaches such as prefabricated and off‑site manufactured homes. Homeowners will gain additional design choices for the accessory dwelling, which could shorten construction time, cut material waste, and give more flexibility in layout and finishes.
Using existing utilities
Owners may tap the current water supply, wastewater and stormwater networks instead of installing fresh infrastructure. The existing capacity must be sufficient and must comply with the national building standards that govern flow rates, treatment levels and connection procedures.
If the property already links to a council or utility provider, the connection can be reused or adjusted for the secondary unit. The provider must confirm the link’s suitability; no building consent is required, although any approvals that the provider normally requires still need to be obtained.
Properties that rely on on‑site solutions—such as rainwater tanks, wastewater treatment units, or stormwater disposal pits—can continue using them for the addition, provided the systems have adequate capacity and meet the relevant code requirements for health and safety.
When municipal or utility services are unavailable or cannot handle an extra load, owners may install a new on‑site system. This option ensures the accessory dwelling remains functional without overburdening existing networks and keeps the overall development footprint small.
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The practical impact is that families can more easily expand their living space without having to maneuver a maze of permits. It also means builders can adopt faster, factory‑based methods while staying within regulatory bounds, which could lower overall costs for small‑scale housing projects.
Updated guidance and resources
From the effective date, revised guidance, quick‑start guides and related documents will appear on the Building Performance website. The materials explain how to apply the exemption, outline the steps needed for compliance, and include checklists that help owners verify that each requirement has been satisfied.
New foundation guidance has also been released, offering practical advice for homeowners and professionals designing footings for the unit under the exemption. The document addresses soil conditions, load calculations, typical installation methods, and the need to coordinate with any existing drainage or utility lines that intersect the proposed foundation area.
Further details on how to submit plans, where to find technical support, and which questions trigger additional review are all covered in the expanded guidance package.
Questions can be directed to the ministry via email at [email protected].
Further information is available online.
