Exemption for Granny Flats: What You Need to Know Before You Build
Building a small standalone dwelling or “granny flat” on your property is a popular way to add space, income, or flexibility for family members. But before you start, it’s important to understand the rules.
The Ministry of Business, Innovation and Employment (MBIE) now allows certain granny flats and small detached dwellings to be built without a full building consent; provided they meet a strict list of exemption criteria. This can save time and money, but it doesn’t mean you can skip the planning or the paperwork.
At Water To Waste Plumbing & Drainage, we’ve broken the exemption down into simple, practical checkpoints to help you decide whether you can build under the new rules or if a consent is still required.
Source: building.govt.nz/granny-flats
🏠 Building Scope
To qualify for the exemption, your building must be:
✅ Detached and standalone – not attached to another dwelling or garage
✅ Single-storey only
✅ Maximum floor area: 70 m² or less
✅ Building Maximum height: 4 metres
✅ Floor level: No more than 1 metre above ground
✅ No mezzanine floors or decks higher than 1.5 metres
✅ Constructed from lightweight materials (walls ≤ 220 kg/m², roof ≤ 20 kg/m²)
These restrictions are designed to keep the structure simple, safe, and within the capacity of standard residential sites.
📐 Site & Location
Your granny flat must also fit within the right location rules:
✅ At least 2 metres from all legal boundaries
✅ At least 2 metres from any other residential building
✅ Cannot straddle a title boundary
✅ Must comply with local zoning, flood hazard zones, and infrastructure availability
It’s worth checking with your local council’s planning maps before you start; especially in areas with flood overlays or shared driveways.
🚿 Plumbing & Drainage
Plumbing and drainage are where most projects trip up. Under the exemption, all sanitary work must comply with the Building Code and be carried out by a licensed plumber or drainlayer.
✅ Must connect to council reticulated services where available
✅ If not available, on-site systems must comply with:
-
G13 (Foul Water)
-
G12 (Water Supplies)
-
E1 (Surface Water)
✅ Onsite wastewater treatment must meet AS/NZS 1547:2012
💡 Tip: Even small dwellings need proper backflow protection, pressure zoning, and soakage assessment. Using a Master Plumber gives you the added peace of mind of the Master Plumbers Guarantee.
👷♂️ Who Can Build
All structural and plumbing work must be done by or under the supervision of licensed professionals:
✅ Licensed Building Practitioner (LBP) for the structure
✅ Plumbers and Drainlayers that are Licensed for water and sanitary connections
✅ Electricians that are Licensed for electrical works and connections
🏛 Council Requirements
Even though consent isn’t required, council involvement doesn’t disappear:
✅ You must notify council before starting work and again once the work is completed
✅ Consent is not required only if every exemption condition is met (EVERY EXEMPTION CONDITION)
✅ The building must still fully comply with the Building Code
⚠️ A Few Words of Caution
An exemption is not a free pass.
-
A Resource consent may still be needed depending on your zoning or site overlays
-
Consideration of the fact that you cannot start work until the exemption is formally accepted is important
-
And yes, you will still need professionals for design, building, electrical, drain laying, plumbing, and (if required) engineering sign-off
Think of this as a low-administration project, not a no-administration one.
Need Help with Your Granny Flat Project?
If you’re planning a granny flat or small standalone dwelling, our team can help you interpret the exemption checklist, design compliant plumbing and drainage layouts, and handle all council notifications.
📞 Call Water To Waste Plumbing & Drainage on 0800 990 069
or
💻 Send an enquiry via our Contact Us page
Areas we service: West Auckland, Kumeū (Physical Branch), Waimauku (the birthplace of Water To Waste), Muriwai, Taupaki, Huapai, Riverhead, Coatesville, Whenuapai, Herald Island, Helensville, Parakai, Waitoki, Woodhill, Kaukapakapa, West Harbour, Hobsonville, Scott Point, Westgate, Massey, Red Hills, Henderson (Our Head office an main branch), Glendene, Te Atatū Peninsula and Te Atatu South, Swanson, Ranui, Glen Eden, Kelston, Titirangi, Green Bay, Blockhouse Bay, New Lynn, Oratia, Sunnyvale, Kelston, Avondale, Sunnyvale, Royal Heights, Lincoln
We’re local, licensed, and here to make the process simple and compliant; so your next build starts off on the right footing. (Pun intended)
