5 Things You Need to Know Before Building a Granny Flat in Canterbury
Thinking about adding a granny flat to your property? Start here.
A granny flat can be a great way to keep family close, create more independent living space or make better use of your property.
But before you choose a design or start comparing prices, there are some important things to understand – particularly in Canterbury, where every property and local authority can have different requirements.
Here are five things we think you should know before you build.
1. Your property comes first
Before you choose a home, understand your site.
It’s easy to start by looking at floor plans. But the first question shouldn’t be “Which granny flat do I like?”
It should be:
“What can I actually build on my property?”
Your section, existing home and site conditions can all affect what’s possible.
Things to consider include:
The size and shape of your section
Where your existing home and other buildings sit
Setbacks and site coverage
Access for people, vehicles and construction
Ground conditions and slope
Natural hazards
Water, wastewater and stormwater
Power and other services
Local planning requirements
Two properties that look similar can have very different building requirements.
Start with your property, not a house plan.
Understanding your site early can help you avoid choosing a design that doesn't work for your section or discovering unexpected costs further down the track.
2. The rules have changed – but there are still rules
Don't assume a granny flat automatically needs a building consent. And don't assume it doesn't.
New national rules introduced in January 2026 have made it easier to build certain small standalone dwellings without a building consent.
For qualifying projects, a dwelling of up to 70m² may be able to use the new building consent exemption, provided all the relevant conditions are met.
Those conditions can relate to the design, size, construction, building professionals, site and other requirements. A Project Information Memorandum (PIM) must also be obtained before work starts under the exemption.
And importantly:
No building consent does not mean no rules.
The dwelling still needs to comply with the Building Code and applicable planning requirements. Other approvals, council requirements, development contributions or site-specific considerations may also apply.
Planning requirements can also vary across Canterbury. Christchurch City, Selwyn, Waimakariri, Hurunui, Ashburton and other districts each have their own planning frameworks.
So don't rely on what a friend, neighbour or someone online tells you they were able to do.
Understand what applies to your property and your project.
3. The advertised house price isn't the whole project cost
This is one of the biggest things to understand before you start.
When you're comparing granny flats, it's tempting to compare one advertised house price with another.
But the price of the dwelling may not include everything required to get your new home ready to live in.
Depending on your property and project, you may also need to consider:
Site costs
Groundworks and excavation
Foundations
Site access
Drainage
Water and wastewater connections
Power and other services
Driveways and paths
Landscaping
Professional and regulatory costs
Surveying
Engineering
Planning or specialist advice
Council fees
Building consent, where required
Other reports or approvals
Optional extras
You may also want to add or change things such as:
Kitchen features
Bathroom fittings
Flooring
Heating and ventilation
Accessibility features
Storage
Decking
Landscaping
Window furnishings
Ask three simple questions.
What's included?
What's not included?
What could change?
A transparent builder should be able to answer all three.
A lower advertised house price doesn't necessarily mean a lower overall project cost. What matters is understanding the whole investment.
4. Design for the person who will live there
A granny flat isn't just a small house.
The best design is the one that works for the person who will actually live there.
Think about their current needs – and what they might need in the future.
For an older family member, that might mean:
Step-free access
Wider doorways
An easy-to-use bathroom
Level-entry shower
Good lighting
Practical kitchen layout
Easy-to-reach storage
Comfortable heating and ventilation
For an adult child, the priorities might be different – more privacy, space to work or study, good outdoor living or room for friends.
And for a multigenerational family, the relationship between the new dwelling and the main home may be particularly important.
Independent doesn't have to mean disconnected.
A well-designed granny flat can give someone their own front door, kitchen, living space and privacy – while keeping them close enough to share a meal, lend a hand or simply know family is nearby.
Think about how the home needs to work, rather than simply how many bedrooms you can fit into it.
5. Who you build with matters
You're making a significant investment. Choose someone you can trust.
Building a granny flat involves your property, your money and often an important decision about your family's future.
You should feel confident about the people you're working with.
Before choosing a builder, ask:
How much experience do you have building minor dwellings?
Do you understand the local Canterbury building environment?
What exactly is included in the price?
What isn't included?
What costs could change?
Who will manage the project?
Who is responsible for each stage?
What happens if something doesn't go to plan?
What warranties and support are provided after handover?
Who can I talk to if I have a question?
And don't be afraid to ask questions that seem obvious.
There are no silly questions when you're building a home.
A good builder should be happy to explain things clearly, tell you when something needs further investigation and point you towards appropriate specialist advice when a question falls outside their expertise.
You shouldn't feel pressured to commit before you understand what you're agreeing to.
Before you build, understand what you're getting into.
A granny flat can be an excellent solution for Canterbury families – whether you're keeping an ageing parent close, helping an adult child take their next step, creating multigenerational living options or simply making better use of your property.
But the right project starts with good information.
Before you choose a home or commit to a price, make sure you understand:
Your property
What can realistically be built and where?
The rules
What planning, building and other requirements apply?
The full cost
What's included, what's not and what could change?
The people
Who will build it and who is accountable?
The outcome
Will the home actually work for the person who will live there?
Understand first. Decide with confidence.
At NZ Granny Flats, we believe our job isn't to talk you into building.
It's to help you understand whether a minor dwelling is right for your family, your property and your budget.
If it is, we'll help you work out what comes next.