Two reforms in January, with further clarification in October

On 15 January 2026, New Zealand introduced a building-consent exemption for certain small stand-alone dwellings under Schedule 1A of the Building Act 2004. Separately, national planning rules created a permitted-activity pathway for qualifying detached minor residential units under the Resource Management Act.

These reforms must be tested separately: one concerns design and building work; the other concerns whether that use of land is permitted. Even when both are satisfied, utility-provider approvals, resource consents for other activities, development contributions and title restrictions may still need attention.

On 8 October 2026, the building exemption was amended to recognise certain certified composite structural building products and clarify public-network connections and qualifying on-site water, wastewater and stormwater systems. The current official reference is the Granny Flats Exemption Guidance, Version 2 .

What actually qualifies for the 70 m² exemption?

The exemption is for a wholly new, detached, single-storey, self-contained dwelling intended for one household. It does not automatically cover garage conversions, additions to a principal dwelling or prefabricated buildings merely because they are advertised as 70 m².

Every exempt dwelling must still comply with the Building Code, including structure, moisture, fire safety, ventilation, energy efficiency and other applicable performance requirements. Exempt construction does not mean a lower building standard.

If the site is affected by natural hazards, the design must make adequate provision to protect the land, building work and other property. Where those risks cannot be adequately addressed, the exemption cannot be relied upon.

The granny-flat myths worth correcting before you buy

Some advertising treats the reform as though everything becomes lawful once a building is smaller than 70 m². The actual exemption is conditional.

Building consent and resource consent are separate tests

The national permitted-activity planning pathway concerns a detached minor residential unit associated with an existing principal residential unit in common ownership on the same site, with no more than one qualifying minor unit per site.

This is not blanket permission to construct a stand-alone house on vacant land. A different district-plan route may exist and needs separate assessment.

The September 2026 amendment clarified that relevant national setbacks are measured from the exterior face of the wall cladding, not the roof eaves or gutters. Schedule 1A's separate two-metre building-exemption requirement must also be met where that exemption is used.

The Ministry for the Environment's September 2026 planning FAQs explain the national standards, district-plan relationship and setback measurements.

When must the granny flat connect to public services?

A 70 m² dwelling can create the water and wastewater demands of a permanent household. It needs a reliable supply for drinking, cooking and washing, compliant plumbing and drainage, a lawful destination for toilet, kitchen, shower and laundry outputs, and suitable stormwater management.

A sewer in the street does not prove that a connection is permitted or that sufficient capacity exists. Ask the relevant network operator to confirm service availability, connection conditions and capacity. An existing septic system must also be checked before accepting additional household flows.

Route A: What must connect when public sewerage is available?

Under the 2026 granny-flat building-consent exemption, applicable water supply and drainage systems must connect to available public network utility operator services in accordance with Schedule 1A. A pipe in the road does not, by itself, prove a suitable connection is available. The owner or designer must establish serviceability, capacity, connection conditions and any operator permissions or charges.

Connecting the dwelling's drainage system does not necessarily mean every toilet must flush into that system or that all suitable greywater must be sent directly to sewer. Building Code G13.3.3 addresses the connection of drainage to an available sewer. Building Code G1 separately recognises non-water-borne sanitation where a healthy and safe disposal system is provided. Government guidance also recognises greywater systems on properties connected to mains sewerage.

For a granny flat beside an existing house, an approved connection through the main dwelling's private drainage may be an option. The pipe route, capacity, gradients, network operator requirements and any required trade or consent approvals must be established; sharing the connection cannot be assumed simply because both buildings are on one property.

A compliant public connection can coexist with an appropriately designed waterless toilet or greywater-recycling system. For a typical sewer-connected household, kitchen wastewater remains connected to sewer , while selected bathroom or laundry water may be diverted to treatment or permitted irrigation. Capturing kitchen greywater is also technically possible, but requires appropriate grease interception, screening, treatment and approvals.

The limitation is important: Schedule 1A's required network connection cannot simply be omitted. Nor does the existence of that connection automatically bring every supplementary system within the building-consent exemption. The additional installation, internal plumbing, treatment, reuse and discharge may require separate assessment or approvals.

Route B: when connection is unavailable or capacity is insufficient

Where the relevant public network is unavailable, or its operator confirms that it lacks capacity, a new on-site system may be possible under Schedule 1A. The complete design must use the prescribed Acceptable Solutions or Verification Methods.

For applicable new on-site foul-water systems, G13/VM4 may be used alongside the specified E1 and G12 methods. Site-specific design must establish expected occupants and flows, treatment performance, soil and groundwater conditions, setbacks, the land-application area, operation and maintenance.

The building-consent exemption does not grant a general exemption from regional discharge requirements or resource-consent conditions.

Route C: when an existing septic or on-site system is proposed

An existing on-site system must have sufficient treatment and hydraulic capacity for the combined household loading, a suitable land-application area, sound physical condition and Building Code compliance. The original approval and any resource-consent limits also matter.

Extending a dispersal field, moving external drains or materially enlarging water-supply or drainage infrastructure may cause the altered arrangement to be treated as a new on-site system for Schedule 1A. Repairs and like-for-like maintenance are generally treated differently.

The 8 October 2026 government guidance sets out the specific compliance methods and limitations in full.

Can a granny flat use a composting toilet or greywater system?

Yes, potentially—with either a conventional flushing toilet or a Waterless Composting Toilet. The important choice is how the household will use, treat, reuse and safely discharge water, while retaining the connections and approvals required for the property.

Waterless Composting Toilets are a recognised sanitation technology. Building Code clause G1 provides for non-water-borne sanitation where the completed arrangement has a healthy and safe disposal system, and AS/NZS 1546.2:2008 is a relevant product standard. Recognition or certification of a toilet does not, by itself, approve the building, drainage, servicing or discharge arrangement.

Connected to sewer? Greywater recycling can still be an option

A requirement to connect to an available public sewer is not automatically a prohibition on supplementary greywater diversion, treatment or reuse. New Zealand Government guidance recognises greywater systems on sewer-connected properties. A compliant connection can remain in service for toilet wastewater, kitchen wastewater and water that needs to bypass the recycling system.

Selected water from showers, baths, bathroom basins and suitable laundry fixtures can be collected for an approved purpose. Depending on the treatment system and the permission for the site, this may include subsurface garden irrigation or higher-quality non-potable reuse. The additional system must still satisfy the relevant plumbing, Building Code, discharge and network requirements. The new granny-flat exemption does not automatically approve every greywater installation.

How diversion and greywater treatment work together

WCTNZ® greywater treatment packages use a diversion arrangement to collect selected household flows and direct them towards treatment. Collection may be gravity-fed or pumped depending on the product and site levels. Where kitchen greywater is included, suitable grease interception and solids screening are placed upstream of the diversion device and treatment system. This is different from collecting ordinary bathroom and selected laundry greywater only.

The diversion arrangement also provides an alternative wastewater route when recycling is not appropriate—for example, when the treatment plant is out of service, storage is full or the incoming water cannot be accepted. Depending on the model, overflow, bypass and filter-backwash or other maintenance wastewater must go to an approved receiving drain or treatment system. Backwash should not be assumed to be a feature or discharge of every model.

On a sewer-connected property, the approved fallback may connect to the existing private sewer drainage serving the main house. On a property with septic or other on-site wastewater treatment, the fallback may return to that system only if its capacity, treatment design, original approvals and land-application area can accommodate those flows. The gravity, pumped and drainlaying arrangements must be assessed for the actual site.

A genuinely Totally Off Grid (TOG) site has no public sewer or conventional septic fallback to rely on. Its design must separately provide lawful control of overflow, off-specification or bypass water, reject and maintenance flows, and any equipment outage. Untreated greywater must not simply be bypassed to the environment.

What do GTS3, GTS2 and GTS1 mean?

GTS means Greywater Treatment System. The numbering used in this Australian-aligned product range describes progressively higher treatment as the number decreases. The following are approximate New Zealand treatment-level descriptions, not automatic product certifications or discharge approvals.

The required performance comes from the actual incoming water, verified system results and the intended discharge or reuse—not from the GTS designation alone. GTS2 and GTS1 represent higher nominal treatment grades than GTS3; “GTS3 or higher” means GTS3, GTS2 or GTS1-level treatment as appropriate.

Can treated greywater supply a flushing toilet or washing machine?

Yes, when the complete reclaimed-water system is designed and approved for that use. A homeowner can keep conventional flushing toilets and reduce fresh-water consumption by supplying appropriately treated greywater to a separate non-potable toilet-flushing circuit.

A higher-quality reclaimed-water system, including an Aqua Clarus-based treatment and polishing arrangement where specified, may also supply the cold-water feed to a washing machine . This is not a claim that every Aqua Clarus or GreyFlow™ Clear unit, on its own and in standard form, produces water approved for laundry or toilet flushing. The designer must verify treatment performance, storage, cross-connection prevention, backflow protection, distribution, operation and approvals for each proposed use.

Prefer a waterless toilet? Greywater recycling remains useful

A properly selected Waterless Composting Toilet eliminates routine toilet-flushing water demand and keeps its sanitation stream separate from other household wastewater. Selected greywater can then be directed towards permitted subsurface irrigation or suitable treatment and reuse—including higher-grade non-potable applications where the full design supports them.

The toilet still needs adequate residential capacity, ventilation, safe service access, treatment or curing arrangements, residual handling and maintenance. Whether separating the toilet stream reduces the size or cost of the remaining wastewater system depends on the actual design, not the label on the toilet.

Three practical household configurations

Kitchen greywater can be treated—with the right pre-treatment

Kitchen greywater is treatable, but it generally carries more grease, food solids, organic loading and detergents than typical shower or laundry greywater. In a WCTNZ® design that collects kitchen water for separate treatment, a suitable grease trap and solids screening are provided before the greywater diversion device and treatment system . The treatment unit and downstream discharge design must be selected for that stronger incoming wastewater.

Where public sewerage is available, the usual simpler choice is to keep kitchen wastewater connected to sewer. That avoids installing and maintaining a separate kitchen grease trap merely to capture it for greywater recycling. On a property served by septic treatment, the kitchen may remain connected to that system if its design, capacity and approvals permit. Where the goal is complete on-site treatment, kitchen greywater can instead be included with the specified pre-treatment and engineering.

The government's greywater-reuse guidance treats untreated kitchen wastewater differently from ordinary domestic greywater suitable for simple diversion. That is not a blanket technical prohibition on engineered kitchen-greywater treatment. Ordinary reuse plumbing generally requires building consent and environmental discharge may require resource consent. Qualifying granny flats have particular Schedule 1A provisions, but these do not automatically approve supplementary recycling or kitchen-water capture.

Can treated greywater discharge to the environment?

Yes, through a suitable and authorised discharge or reuse arrangement. A correctly specified greywater treatment system may produce treated effluent suitable for designed land application, subsurface irrigation or another permitted environmental discharge. The acceptable outcome depends on actual treatment performance, wastewater inputs, soils, groundwater, site conditions and relevant regional rules or resource consent.

Higher treatment can expand the practical options, but a treatment level alone does not authorise unrestricted discharge to a watercourse, land or groundwater. A compliant environmental receiving system must be part of the complete design; treated water does not automatically need to return to public sewerage or septic treatment.

Totally Off Grid (TOG): designing the complete system

For a Totally Off Grid (TOG) property without public sewerage or an existing septic treatment route, WCTNZ®'s standard treatment-based configuration separates the toilet waste with a suitably sized Waterless Composting Toilet and treats the remaining household greywater, including kitchen water where specified.

GTS3 is WCTNZ®'s standard treatment baseline for the described TOG package, not a universal New Zealand legal minimum. A separately engineered low-treatment diversion design may be acceptable on the right site. Conversely, difficult ground conditions, sensitive receiving environments or a demanding reuse application may justify GTS2- or GTS1-level performance and further polishing.

Eight steps before and during the build

Confirm the legal requirements and the water, wastewater and stormwater arrangements before finalising the building package or bathroom layout. The owner, designer, licensed trades and any wastewater specialist should agree on occupancy and servicing assumptions from the outset.

Consent-exempt does not mean cost-free

The exemption does not remove costs for design, PIM fees, licensed work, foundations, surveys, utility connections, on-site wastewater infrastructure, possible development contributions or insurance. There is no ordinary council inspection programme or Code Compliance Certificate for exempt work, but councils can investigate or enforce compliance. The owner and licensed professionals remain responsible for safe construction and accurate records.

Granny-flat rules and wastewater FAQs

Official 2026 granny-flat guidance and forms

This resource draws on official government guidance. Property owners and professionals should check the current legislation and the requirements for their specific property before making irreversible decisions.

Continue into the practical sanitation pathway

Important limitation

This page is general building, regulatory and product-pathway information. It is not a legal opinion, building-consent exemption determination, wastewater design, engineering assurance or approval of a site. Confirm the current legislation, network conditions and local or regional requirements with appropriately qualified people before committing to a project.