Thinking About Building a Granny Flat? Here’s What You Need to Know First

Granny flats, also known as minor dwellings, minor residential units, or secondary dwellings, have never been more popular in New Zealand. Whether you’re looking to house ageing parents, bring extended family onto the property, create a rental income stream, or simply add long-term value to your land, a granny flat can be an excellent solution.

The rules have also changed significantly. As of January 2026, the Government has removed both the building consent and resource consent requirements for granny flats up to 70 square metres that meet certain conditions, making it faster and cheaper to get one built. But “no consent required” doesn’t mean “no rules apply.” There are still a lot of matters to work through before you start pouring a slab, and getting them wrong can be expensive.

Here’s what you need to know.

1. The New Consent-Free Rules and What They Actually Mean

Since 15 January 2026, granny flats up to 70m² can be built without a resource consent or a building consent, provided they meet the conditions set out in the new National Environmental Standards for Detached Minor Residential Units (NES-DMRU) and the Building Act exemption criteria.

This is a significant change, but the exemption is not a free pass. The key conditions include:

• The dwelling must be no more than 70m² in floor area

• It must be a standalone, detached structure (not attached to the main dwelling)

• It must be set back at least 2m from the boundary and 2m from other buildings on the site

• It must be no more than 4m in height above floor level

• Specific requirements apply to cladding, roofing, framing materials, and connections to water, stormwater, and wastewater

• All work must be carried out or supervised by a Licensed Building Practitioner (LBP)

• The build must still comply with the New Zealand Building Code in full

• You must still apply for a Project Information Memorandum (PIM) from your local Council.

If your proposed granny flat doesn’t meet all of these conditions, you will still need a resource consent, a building consent, or both. Understanding which side of the line your project sits on is the starting point for everything else.

2. Your District Plan May Be More Flexible Than the National Standard

The NES-DMRU sets a national baseline, but your local council’s District Plan may already allow granny flats on more generous terms. Some councils permit minor dwellings up to 90m² as permitted activities, with their own set of standards around setbacks, site coverage, and design. In some cases, the District Plan rules are less restrictive than the national standard.

Checking both the NES-DMRU and your local District Plan is important, because you want to know the most permissive pathway available to your project, not just the national one. A planning assessment will tell you which set of rules gives you the most flexibility.

3. Size Matters, But So Does Site Coverage

The 70m² size limit is what most people focus on, but it’s not the only spatial constraint on your project. Your District Plan will also set limits on:

Site coverage: The proportion of your total site that can be covered by buildings. If your existing house and any outbuildings already take up a significant portion of your section, a new 70m² dwelling may push you over the coverage limit even if the flat itself meets every other rule.

Outdoor living space: Many residential zones require a minimum area of usable private outdoor space per dwelling. Adding a second dwelling to a site can make it difficult to meet this requirement without careful layout planning.

Setbacks: Even under the consent-free rules, the flat must sit 2m from boundaries and from other structures. On a small or irregularly shaped section, this can meaningfully constrain where the flat can be sited and how large it can practically be.

Running a site analysis before you commit to a floor plan will save you from designing something that doesn’t physically fit within the rules.

4. Servicing: Water, Wastewater, and Stormwater

A granny flat is a separate dwelling, which means it generates its own demand on water, wastewater, and stormwater systems. Even under the consent-free pathway, you are still required to connect the flat to these services in compliance with the Building Code.

Key questions to work through before you start:

• Is there sufficient capacity in your existing water supply connection to service a second dwelling?

• Can your existing wastewater connection handle the additional load, or will you need to upgrade?

• How will stormwater from the new roof and impervious surfaces be managed and discharged?

• If you’re on a rural property without reticulated services, what are the on-site options for water supply and wastewater treatment?

Getting a civil engineer or plumber to assess your servicing situation early, before you finalise a design, prevents costly surprises during construction.

5. Development Contributions

Even though you may not need a resource consent or a building consent, councils may still charge development contributions when issuing a Project Information Memorandum (PIM) for your granny flat. These are fees that fund the additional demand your new dwelling places on community infrastructure such as roads, parks, and water networks.

The amount varies between councils and zones, but development contributions are a real cost that needs to be factored into your budget from the beginning. Overlooking them is one of the most common ways people underestimate the total cost of adding a second dwelling.

6. The Project Information Memorandum (PIM)

Even without a consent requirement, obtaining a PIM from your council before you build is required. A PIM is a formal document that sets out the relevant planning and building information for your site, including:

• Any known hazards (flooding, liquefaction, slope instability)

• Drainage requirements

• Any existing consent notices or covenants on the title that might affect what you can build

• Development contributions that will apply

  
  

A PIM protects you by providing official council information at the outset, rather than discovering a problem partway through construction or at the point of sale.

7. Title Covenants and Consent Notices

Before you get too far into planning, it’s worth checking whether your title has any covenants, consent notices, or other legal instruments registered on it that restrict additional dwellings. These are common on newer subdivisions and on sections that have been through a resource consent process previously. They run with the land regardless of what the District Plan or national standards now allow, and they cannot simply be ignored because the rules have changed.

A pre-purchase property check or a title search will identify any such instruments before you invest in design work.

8. Existing Structures and Compliance

If you’re thinking of converting an existing structure (a garage, sleepout, or shed) into a granny flat rather than building new, the rules are more complex. The consent-free pathway applies to new standalone dwellings built to the specific design criteria, not to conversions of existing non-residential structures. Converting an existing building is likely to require a building consent and potentially a resource consent as well, depending on what changes are being made and what the original structure was consented as.

9. Rental Use and Tenancy Obligations

If you plan to rent your granny flat out, you become a landlord under the Residential Tenancies Act 1986. That means the flat must meet the Healthy Homes Standards (covering heating, insulation, ventilation, moisture ingress, and draught stopping) before a tenancy can begin. These standards apply regardless of whether the flat was built under the consent-free pathway or through a full consent process, and they are increasingly enforced.

10. Insurance and Finance

Adding a second dwelling to your property has implications for your insurance and potentially your mortgage. It’s worth checking with your insurer before you start construction to ensure your policy covers the new structure during the build and once it’s complete. Some policies require notification of any additions or changes to the property. Similarly, if you’re planning to refinance or access equity to fund the project, your bank will want to understand the nature of what’s being built.

Consent-Free Doesn’t Mean Advice-Free

The removal of consent requirements is genuinely good news for New Zealand homeowners. It reduces red tape, lowers direct costs, and can cut up to 14 weeks off a project timeline. But the rules that remain are still technical, and the consequences of getting them wrong, including demolition orders, fines, or an uninsurable structure, are serious.

The smartest first step is still a planning assessment. Understanding exactly which rules apply to your site, what your section can realistically accommodate, and whether your project qualifies for the consent-free pathway or needs a consent application is far cheaper to establish at the planning stage than to discover mid-build.

Thinking about a granny flat?  Get in touch for a free 30-minute consultation. We’ll give you a straight answer on what your site can achieve and what pathway makes the most sense for your project.