Advice On Converting Your Garage To A Granny Flat (NZ)

We’ve been getting quite a bit of requests recently about building a sleepout, extending the house, adding another level and converting a garage to a new living space. So we’ve put together this article to answer a few questions, and to provide some advice to those exploring this idea.

Life doesn’t always remain constant this applies to our needs as well! If you’re planning on converting your garage into living space, then it’s likely that your needs have shifted. Moving may not be an option for a number of reasons, you love your location, love your home, buying a new home is too expensive, and it’s probably not the best time in the market to sell.

Converting your garage into a new living space is not a simple and easy decision and there is quite a bit to think about to ensure you’re making the right decision. This is part of the reason why we created this article to explore some of those questions, so you can make an informed decision.

With our circumstances continually changing, our needs and desires evolve. But that doesn’t mean we have to get rid of the things that are of little or no use to us temporarily. When you bought the house, no doubt you would have thought about it long and hard until you found the right one, but now you need more space for your growing family or perhaps a space as a home office (the options are endless). So naturally extending your home or converting a space comes to mind, utilizing your garage and converting it into a liveable is one of the more popular options but here are a few things you need to think about.

Is my Garage Suitable to be converted into a Granny Flat?

The first and foremost question is the suitability of the room and whether or not it is capable of conversion. The height of the ceiling from the floor must be more than 2.4 meters; however, while designing a garage most of the time, we tend to keep the roof lower.

Next is the weather resistance of the garage. Originally being an area to park your vehicle, bikes, and store tools, we don’t pay enough attention to the water drainage. If the water drainage of your garage is not up to the standard, then it may risk water ingress and moisture build up.

Is converting the garage into a granny flat the right choice?

Firstly, what is a granny flat? Auckland City council doesn’t have a separate category for granny flat or minor dwelling units, but it simply means any flat that has a kitchen is considered to be a second household unit.

Why you need extra space? do you need a room for your child or parent? Perhaps you’re looking to rent out the un-used space? If you are just seeking extra space (with the kitchen or bathroom), then adding an extension to your home could also be an option.

There could be other reasons for the extra space, and it may not be a granny flat that you’re needing. It is common in new homes to have a media room, study room/office, recreational area, or a game room – all of which is not considered a second household unit.

You need to determine what kind of room you’re looking for, whether it’s an extra household unit, extra bedroom, a study room, or a recreational room – this will determine the scope of works for the architect.

There are multiple ideas available to use spare space. You can convert your garage into following areas:

  • Work from the home area
  • Gym area
  • Gaming area
  • Hobby room
  • Media room or movie theatre
  • Teenager’s room
  • Guestroom
  • Rented out for extra income
  • Home entertainment/bar space

A garage conversion is a place that offers quite a wide range of possibilities and because it’s a existing building/space – it requires less planning and investment compared to a new extension. But before you explore ideas, you need to consult with  an architect to see is there are any limitations.

Other considerations

Here are a few other things to think about as well before you jump into it:

  • Where will you park your vehicle if the garage gets converted into the room?
  • What would the house look like after the transformation?
  • How spacious or large is your garage? Is it worth a conversion or is it just the waste of time, effort and money?
  • Do I require building consent for the garage conversion?

Does a garage conversion require building consent?

You will need to first consult with an architect to carry out a feasibility study which will determine whether it’s even possible to utilise the garage space.  For a basic garage conversion to a living space, you will require building consent because the garage is not considered a habitable space. Bathrooms are allowed if they meet the rules, but you can’t put a kitchen and laundry into a basic conversion.

All the work that needs to be done to convert your garage into a living room must also be done in accordance to the standards set out by the building code. A garage being a non-habitable structure is a Class 7.0 residential outbuilding. So when you decide to transform it into a living room which will be habitable, then it will be reclassified into Class 2.0.

However, if you are thinking about converting your garage into a minor dwelling (second household unit), then you will be both building consent and resource consent. Resource Consent is required to ensure the project meets the provisions of the Resource Management Act, which for buildings are usually covered by the District Plan -or in Auckland, the Unitary Plan…. Building Consents are required to ensure the project meets the provisions of the Building Code. (Reference from Pacific Environments)

If you are living in or near Auckland, then it is important to determine your zone before seeking any permission to convert. The rules might vary according to the zone, and you need to be certain as to what rules apply when it comes to change in the use of a building or the development of an extra dwelling – your architect will be able to help you with this.

The Auckland Unitary Plan has set the ground rules for all kinds of future developments, expansions, and intensifications covering Auckland and the nearby areas. This unitary plan focuses on the rules to control how the areas must develop in the future.

To determine the details about your zone, all you need to do is to go to the Auckland council site and search for your zone. You will find all the details regarding your zone available on the following website:

We still highly suggest talking to your architect, or a planner to get the best possible advice. Getting all the information regarding your zone and the building rules that applies to you will help avoid all kinds of future complications and conflicts.

What Features Of Building Code Do I Need To Keep In Mind?

  • Fire Safety: The fire safety feature encourages to take measures regarding fire accidents, including the construction of safe escapes and installation of smoke alarms.
  • Energy efficiency: The use of natural resources to provide for comfort is also a clause in the Code. You have to introduce adequate lighting, humidity, and ventilation sources to comply with the requirements.
  • Durability: The durability feature stress that the material needs to be used in the building will stay functional until the estimated life of the building.
  • Sanitary measures: You must have to pay attention to all kinds of sanitary fixtures, including water, gas, and electricity.
  • Moisture prevention: You must have to keep an eye on the drainage system for all kind of penetrating and pouring water.
  • Ceiling height: One of the most crucial factors in building a room is the ideal height of the roof. The height of the living room must not be less than 2.4 meters. If the roof of your garage is lower than 2.4 mark, then you may consider raising the ceiling. Lowering the floor could be an option, but it requires more effort and investment.

If the walls of the garage are made of brick then it will require an additional layer of protection using membrane or the weather-resistant paint. The additional membrane will help provide protection against dampness. You can also opt in stud wall if you’re looking to secure electrical wiring and insulation.

In regards to the floor of the garage, you have to ensure that it has waterproof protection to avoid dampness and water retention. The floor of the garage is mostly commonly made of reinforced concrete, and wouldn’t have any additional protection. There are a variety of products available in the market that can help you with waterproofing the floor.

Another thing to consider is ventilation, you may want to introduce more air flow and ventilation by choosing to install a large window replacing the garage door. The requirements for the natural light in the living room have been pen down in the clause G7 of the Building Code. You can measure your natural light requirements using a lux meter.

The room will also require additional electrical outlets, which most registered eletricians will be able to do. Make sure to Hire a registered electrician because they will need to provide the necessary compliance certificate regarding all the wiring work that has been done – which will be needed when you’re applying for your Code of Compliance Certificate.

You’ll also need to be aware that converting your garage into a habitable room, you will also need to look at issues with the rainwater. Most of the garages use a slanted floor to drive rainwater outside the garage into the drain. But once you decide to convert the garage into the living area, you’ll need to address the water flow issue – perhaps installing additional drains.

Unconsented garage conversions

If garages are converted into living spaces without the appropriate consents and certifications, future owners of the property may have problems insuring the property – even if a pre-sale building inspection identifies no issues.

It may, therefore, be difficult to sell the property – at best, there could be a delay before a sale and purchase agreement becomes unconditional.

We recommend that you advise your clients to contact the council and apply to have any unconsented conversions certified before they list a property. This will save time and stress during the sale process. (Reference from

Converting a garage into an additional dwelling

So you’re still keen on converting your garage to an extra household unit. Various aspects come into play if you are thinking about separate dwelling compared to just converting it to a usable space, an extra dwelling means it includes a new kitchen and bathroom as well. The additional construction will require resource consent and building consent from the Auckland Building Council.

What does converting a garage to a extra house unit mean Financially?

Adding a self contained unit, or ‘granny flat’ to your home can be a cost effective way to provide a home for elderly relatives or older children struggling with rising rent. It can also be a great way for homeowners and investors to generate extra cash flow through rental income and increase the property’s overall value.

With rental yields of anywhere between $200-$600 a week, granny flats can be a great strategy if you’re looking for a long-term return on investment. Not only do they provide a second income, you can also benefit from positive gearing and extra claimables on your depreciation schedule. In an area where rental demand is high, a granny flat can stand out from the competition when it comes to selling. (Referenced from Loan market, 2017)

Attached or detached? 

Your ‘granny flat’ can either be a stand-alone dwelling or an extension of your house (e.g. if you convert your garage or your basement).

Factors To Consider While Opting For a Garage Conversion

Although the garage will work just perfectly with your existing space, you have to make some necessary alterations to make the new room blend in with the rest of the home.

  • Replacement for a garage door: Replacing the large garage door is a must, there are plenty of options available when it comes to door replacement, including a window, wall, or a patio door.
  • Is there enough lighting? Where is it coming from? If the garage already has a window, then replacing the garage door with extra windows will also offer you extra lighting. Even if there is no sufficient source of natural lighting in the room, you can always opt for artificial skylights as well. The lighting choice in the newly converted room depends on your usage of the room.
  • What about the garage floor? Mostly garages are concrete flooring, and if you are planning on using the room as the gaming area or the media room, you can opt for standard carpet or wooden floors. However, if you are thinking about converting your garage into a guest room or granny flat, then your options may lean more towards comfort (eg extra layer of insulation under the carpets)
  • How to utilize the space? If you are planning to convert the garage into a small dwelling or a granny flat, utilising the given space will be important and it’s balance between necessary functions and space. For example, if it’s a small space, it may be better of going for a open plan kitchen, living area and laundry – as opposed to partitioned off.
  • Where to park the car? The consequence of transforming a garage into the habitable living room is the loss of parking area for your car.

An example of a converted garage

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What is the cost to build a granny flat (nz) detached?

The cost of building a granny flat detached from the main house can vary quite a bit, and the 3 main factors it comes down to are the size of the build, your region, and the complexity of the build/materials. There are of course cheaper options as opposed to building from scratch such as kit sets or prebuilt granny flats. If you are intending to build from a plan, the average price for a granny flat starts around $90,000 plus GST and can go up to $150,000 mark, plus GST.  


How much does it cost to convert a garage into a room?

The cost of building work for converting a garage to a room can average around $1,250 – $1,500 per square metre not including the cost of architect fees, building/resource consent fees, escavation and engineer fees. Typical garage conversion to room (30m2) will range from $37,500 – $45,000.


How much does it cost to convert a garage to a granny flat?

The cost of building work for converting a garage space to a granny flat which includes a new kitchen and bathroom ranges from $1,750 – $2,150 per square metre not including the cost of architect fees, building/resource consent fees, escavation and engineer fees. Typical garage conversion to granny flat (30m2)  will range from $52,500 – $64,500.  A minor dwelling can cost up to $20,000 in plans, consents, and development contributions and connections before any building work takes place.

If you’re still deciding what to do with the unused space, make sure to consult with professionals (architects, builders/project managers, and financial advisors) as well to get different perspectives on the situation so you can make an informed decision that will benefit you in the long term.




Please note: Whilst all information is considered to be true and correct at the date of publication, changes in circumstances after the time of publication may impact on the accuracy of the information. The information may change without notice and Superior Renovations is not in any way liable for the accuracy of any information printed and stored or in any way interpreted and used by a user.


To wrap up

How much does it cost to convert a garage into a room?

Typical garage conversion to room (30m2) will range from $37,500 – $45,000.

How much does it cost to convert a garage to a granny flat?

Typical garage conversion to granny flat (30m2) will range from $52,500 – $64,500.

Do I need building consent for converting my garage to a granny flat?

You will need to apply for building consent if you're converting your garage to a room, if you're converting it to a minor dwelling (with kitchen and bathroom) then you will also need to apply for resource consent.


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