129: How the new granny flats building consent exemption is changing restricted building work for LBPs

The new granny flats building consent exemption allows certain new small standalone dwellings up to 70 square metres to be built without a building consent provided all exemption conditions are met and the work is carried out or supervised by licensed building professionals.  

Because councils will not review or inspect exempt work, Licensed Building Practitioners (LBPs) play a central role in ensuring these buildings are still designed and constructed to comply with the Building Code. 

This article outlines what the exemption means for LBPs, including where responsibilities have increased. 

What the exemption allows

A new, single-storey standalone dwelling up to 70 square metres can be constructed without a building consent if it meets all criteria in Schedule 1A of the Building Act 2004. This includes but is not limited to:

• it meets the requirements for a detached dwelling, as defined in clause A1 of the Building Code
• it has a maximum height of 4 metres above the floor
• it has a floor level of up to 1 metre above the supporting ground
• it must not contain a mezzanine floor
• it has a frame made of lightweight building products (being steel or timber)
• it is at least 2 metres away from any other residential building or any legal boundary
• it is built using lightweight building products for the roof that have a maximum weight of 20 kilograms per square metre
• its wall cladding has a maximum weight of 220 kilograms per square metre or less
• its water supply, sanitary plumbing, and drainage must meet specific requirements
• it must have an independent source of supply for electricity and, if gas is to be used in the dwelling, an independent source of supply for gas
• where heaters are installed, they must be either electric or gas heaters
• it does not have a level entry shower requiring a waterproof membrane.

The work must be carried out or supervised by licensed practitioners. If the granny flat does not meet all the exemption conditions the building work requires a building consent.

These criteria are in addition to the requirement that the building be built to the Building Code. The New Zealand Building Code consists of 3 general clauses (A1–A3) and 38 technical clauses (B1–H1). These mandatory, performance-based clauses cover stability, fire safety, moisture, user safety, services, and energy efficiency.

What this means for Design LBPs

Designers retain their existing RBW obligations, but the exemption increases the importance of accuracy and clarity because councils will not review design documentation.

1. Confirming the project qualifies

Designers must ensure the design meets all exemption criteria. A single non-compliant feature, such as exceeding the 70 square metre limit or including heavy wall cladding, moves the work outside the exemption and triggers the need for a building consent.

2. Producing clear, compliant designs

Designers must clearly demonstrate how the design complies with all the relevant Building Code clauses, particularly:

• B1 Structure
• B2 Durability
• C1–C6 Fire Safety
• E2 Weathertightness

Without council review, documentation must be clear and easily understood by other LBP’s during the construction phase.

3. Completing updated MBIE documentation

Designers must provide a Certificate of Work (CoW) for the design of RBW, using Form 2A: Memorandum from licensed building practitioner (certificate of design work).

Granny flats exemption: Guidance and resources(external link) — Building performance 

These documents become the primary evidence of Building Code compliance because no building consent or Code Compliance Certificate will be issued.

Under the exemption, a designer’s involvement is likely to extend further into the construction phase than in a standard consented project. Final plans and supporting documentation must accurately reflect the building as completed, which may require the designer to stay engaged until construction is finished.

Designers may wish to review and update their contracts, ensuring they clearly capture this ongoing involvement, including obligations to verify that the final build aligns with the approved design documentation and exemption criteria.

4. Supporting the homeowner

Designers should advise homeowners to:

• obtain a Project Information Memorandum (PIM) before work begins
• notify the council before starting and after completing the work
• avoid unapproved design changes during construction, which may invalidate the exemption.

What this means for Builder LBPs

Without council inspections, builders are responsible for verifying that construction is carried out exactly as designed and complies with the Building Code.

1. Building strictly to the approved design

On-site changes can unintentionally breach exemption conditions. Even minor adjustments to layout, claddings, foundation details, or drainage systems may trigger the need for a building consent.

2. Self-checking for Building Code compliance

Traditional inspection steps are not carried out by councils. Instead, during construction, builders are responsible for ensuring building work complies with the Building Code in areas such as:

• structural framing and bracing
• foundation preparation and reinforcement
• cladding systems, flashing installation, and weathertightness detailing.

3. Managing and supervising subtrades

All plumbing, drainage, gasfitting, and electrical work must continue to be performed or supervised by appropriately licensed professionals.

Builders should ensure:

• subcontractors hold correct licence classes
• all relevant RoWs are completed and collected
• work aligns with the original compliant design documentation

4. Completing documentation

Builders must provide the homeowner with a RoW for restricted building work they carried out or supervised - if more than one builder carried out or supervised restricted building work they each need to provide a RoW for their work.

The builder must also provide this to the council that issued the PIM. These documents protect both the builder and the homeowner and may be reviewed in future insurance or legal processes.

5. Communicating clearly with the homeowner

Builders should ensure homeowners understand:

• a PIM must be obtained from their local council before work starts
• no council inspections will occur
• non-compliant changes can invalidate the exemption and create enforcement or insurance issues.

Clear communication reduces misunderstandings and protects all parties from disputes.

Conclusion

The granny flats building consent exemption has not changed what constitutes Restricted Building Work, but it has fundamentally changed how RBW is verified. LBPs must ensure granny flats are designed and built to meet the exemption conditions and are compliant with the Building Code.

Designers and builders who understand the exemption criteria, maintain strong communication, and produce clear documentation will help homeowners realise the benefits of faster, lower-cost construction, while upholding building quality and safety.

Quiz

1. Under the granny flat exemption, who has the responsibility during construction to ensure that all building work, including any RBW, continues to comply with the Building Code and the conditions of the exemption?
a) The local council
b) The homeowner
c) Licensed Building Practitioners (LBPs)
d) The building inspector

2. What is still required for structural and weathertightness work in an exempt granny flat?
a) A full building consent
b) A Licensed Building Practitioner to carry out or supervise the work
c) Council inspections at key stages
d) A Code Compliance Certificate

3. What happens if a change pushes the project outside the granny flat exemption criteria?
a) Nothing - the build remains exempt
b) The homeowner only needs to notify the council
c) The project may require a building consent or Certificate of Acceptance (if already built)
d) The builder may approve the change themselves