Building Your Granny Flat Step by Step

Call, email, or fill out an enquiry form on our website. Tell us roughly what you have in mind — where the property is, what you want to build, and any timeline or budget ideas.

• No commitment required at this stage
• We'll let you know if the granny flat exemption is likely to apply to your situation
• We can also flag if you might need a standard building consent instead

We'll review your site details and discuss whether your proposed granny flat qualifies for the consent exemption. The dwelling must meet all of these conditions:

• New build only — not an addition or conversion of an existing structure
• Single storey (no mezzanine)
• Standalone — not attached to another building
• 70m² or less (internal floor area)
• At least 2 metres from any boundary or other residential building
• Lightweight timber or steel framing

Before any design work, we need to understand your site properly. You'll need to check a few things with your council, and we'll assist throughout.

• Check the NES-DMRU (National Environmental Standards) — this determines if you also need a resource consent under the RMA
• Review your council's district plan for any site-specific rules
• Identify any natural hazards (flooding, slippage, erosion, subsidence)
• Check if development contributions will be payable (amounts vary by council)
• Speak to your bank and insurer early — they'll want to know what documentation to expect

ArchSolutioNZ acts as your Licensed Building Practitioner (LBP) designer. We'll provide a written contract outlining the scope of design work, fees, and responsibilities.

• We strongly recommend having your lawyer review the contract before signing
• The contract covers preliminary plans, the PIM application, full construction plans, and the Certificate of Work

We prepare preliminary design plans to accompany your PIM application. These include site plans, elevations, and basic sections.

• Plans show the building is standalone, new, ≤70m², and single storey
• Natural hazard mitigation is incorporated where required
• You review and approve the preliminary design before the PIM is lodged

The PIM is a mandatory step — you must receive it before any building work begins. We'll help you prepare the application (Form 2AA) and submit it through your council's portal.

• Submit: completed Form 2AA, preliminary design plans, and description of the proposed work
• Pay the council's PIM application fee (amount varies by council)
• The PIM is not an approval — it's an information document from the council about your site

The council reviews your application and issues the PIM along with additional information about your site. It will include:

• Whether your proposal appears to meet the exemption criteria
• Any natural hazards identified on your land
• Relevant heritage status, bylaws, infrastructure availability, and district plan requirements
• A development contribution notice if applicable (stating the amount you'll need to pay on completion)
• Confirmation that you have two years from this date to complete the build

We carefully review all council-provided information and update the design as needed. We then develop the complete construction plans and specifications.

• Full architectural plans including structure, cladding, plumbing and drainage layout
• All plans checked against every relevant Building Code clause
• We issue a Certificate of Work (CoW) — our formal declaration that the design complies with the Building Code
• Final plans and CoW are provided to you

Because there's no code compliance certificate issued under the exemption, lenders and insurers need other assurances. Set this up early so there are no surprises.

• Provide your lender with the PIM, preliminary design plans, and information about your licensed professionals
• Confirm with your insurer what documentation they'll require at completion
• Arrange construction insurance to cover the build period
• Ask about stage payment release requirements — your lender may want QA reports at key stages

All restricted building work on your granny flat must be carried out or supervised by a Licensed Building Practitioner (LBP). You can verify any builder's licence at lbp.govt.nz.

• Get at least two or three quotes
• Check the builder's LBP licence class covers the work (structure, external moisture management)
• Confirm they have appropriate insurance in place
• Ask what warranties they offer beyond the 12-month statutory defect repair period
• The builder must provide a disclosure statement and standard checklist before you sign anything

For any residential building work costing $30,000 or more, a written contract is mandatory under the Building Act. This protects both you and your builder.

• The contract must cover: scope of work, timeline, payment schedule, and dispute resolution
• Have your lawyer review the contract before signing
• The contract must also specify who is responsible for obtaining approvals and collecting documentation
• Implied warranties apply for 10 years regardless of contract terms

The builder, tradespeople, and site manager work to the plans and specifications. Unlike normal consented work, there are no mandatory council inspections — so your own quality assurance is critical.

• All work must comply with the New Zealand Building Code
• The builder must supervise any unlicensed workers (eg apprentices)
• Plumbing, drainage, gas, and electrical work must be carried out by appropriately licensed tradespeople
• Your two-year PIM clock is running from the date the PIM was issued

Because the council does not inspect exempt work, you are responsible for ensuring quality checks happen. We strongly recommend professional QA inspections at each of the following stages:

• Foundations — before concrete is poured; confirm location and structural soundness
• Framing — before roof cladding goes on; check structure, bracing, and load capacity
• Building wrap — before joinery is installed; critical for weathertightness
• Pre-clad — check flashings and cavity systems for moisture management
• Pre-line — insulation and services installed, building weathertight, before linings go up
• Drainage — before trenches are filled in
• Final — all work complete, ready for occupation

On-site changes happen. But any variation must be checked to confirm it doesn't breach the exemption conditions or the Building Code. Do not proceed with a change without first consulting us.

• We assess the variation for compliance with the exemption conditions
• If compliant, we update the drawings and revise the Certificate of Work
• If a variation takes the build outside exemption conditions (eg floor area exceeds 70m²), all work must stop and a building consent must be obtained before continuing
• Product substitutions (eg different cladding or roof material) must also be checked — they can affect the weight limits set in the exemption

Under the Building Act, your granny flat is considered legally complete only once you have received all of the following from your licensed professionals:

• Final design plans (updated to reflect what was actually built, including any variations)
• Certificate of Work (CoW) from ArchSolutioNZ covering all restricted design work
• Record of Work (RoW) from each LBP builder for restricted building work they carried out or supervised
• Record of Work from your registered plumber/drainlayer for sanitary plumbing and drainage
• Electrical certificate of compliance and electrical safety certificate
• Gas certificate of compliance and gas safety certificate (if gas was installed)

Once you have received all required documents (Step 15), you have 20 working days to submit them to the same council that issued your PIM. The council stores these on your property file — they do not assess them for compliance.

• Submit: final design plans, Certificate(s) of Work, Records of Work (from LBPs and plumber/drainlayer), electrical and gas certificates
• Note: LBPs are required to submit their Records of Work directly to the council as well — but you should confirm this happened

If the council issued a development contribution notice alongside your PIM, you must pay it within 20 working days of completing the build. The amount was fixed at the PIM stage.

• Amounts vary by council, size of the granny flat, and whether NUO connections are required
• Payment can be made to the council directly — check the contribution notice for details
• If the design changed significantly during the build, discuss with the council whether the amount needs reassessing

Your bank may need to release final drawdown funds, and your insurer needs to switch from construction cover to permanent dwelling cover.

• Provide: final plans, Records of Work, Certificates of Work, energy safety certificates, and proof of council submission
• Confirm natural hazards commission (EQC) cover eligibility with your insurer
• No code compliance certificate is issued under the exemption — your documentation package replaces this for insurance and lending purposes

Congratulations — your granny flat is now a lawful building under the Building Act. Keep all documentation stored safely, as you'll need it for:

• Future alterations (any changes to the granny flat follow the rules for existing buildings — some work may need a building consent)
• Selling your property — your granny flat records will appear on the LIM
• Insurance claims — insurers may ask to see your Records of Work and plans
• Defect claims — your builder is liable to fix defects for 12 months; implied warranties run for 10 years