All the things you need to know about building a granny flat

Granny flats have come into their own in as versatile dwellings with multiple uses. Here’s what you need to know

As the world has reviewed what ‘normal life’ means over past few years, many of us have re-evaluated our living situations thanks to spending more time at home. We’re looking at our surroundings with new eyes, not just at decorating with wellbeing in mind, but with a more open-minded approach. Being at home more for work and play means we’re using spaces differently and embracing more diverse households.

Whether you need a home office or somewhere to house a family member who wants some independence, separate dwellings or granny flats built on your existing property provide privacy while staying close by.

What are separate dwellings?

This type of dwelling is generally defined as secondary to the principal residence on a site, with kitchen and plumbing facilities. Its purpose is to provide accommodation but is limited in size.

What rules should I follow?

The Building Act 2004 is the primary legislation regulating separate dwellings. Each local authority sets its own rules, so it’s essential to contact your council to be clear on the guidelines and fees when building a separate dwelling.

Dave Gittings, manager of building performance and engineering at the Ministry of Business, Innovation and Employment, advises people to take note of the Resource Management Act (RMA) too, as this has additional requirements: “Regardless of whether a building consent is needed, all building work must comply with the Building Code and other relevant legislation such as the RMA.”

You may hope to rent out your dwelling; if so, it must follow requirements under the Healthy Homes Guarantee Act 2017 and Residential Tenancies Act 1986, including the Healthy Home Standards.

How big can I build?

Sizes of separate dwellings vary between councils, so it is best to get in touch with your local one for clarity. In Auckland, minor dwelling floor areas should not exceed 65sqm, excluding decks and garaging (other standards apply too).

Do I need a consent to build?

All new building work must follow the Building Code and the Building Act sets out the rules regarding building consents. From here, each local authority generally determines its consent process (meeting the Building Act and the Building Regulations requirements). Your local council can inform you of consents for your area.

For instance, under the Auckland Unitary Plan, a building consent is required, and
a resource consent may be necessary, depending on the zone you live in. Some companies can take care of the design, consent and construction process for you, saving any potential headaches. They also understand the council regulations you’ll need to follow.

If you’re wondering how far you can build from the edge of your property, there is no single minimum or maximum distance a building can be from a boundary, Dave says, “This will depend on requirements in the district plan as well as Building Code requirements for things like protection from fire and natural light amongst others.”

Types of separate dwellings

Build your own

If you’re constructing a separate dwelling, treat it as the same process as a standard house. Ask a builder for a quote, have plans drawn by an architect or draughtsman, then send them to contractors to price up. By doing it yourself, you can create a bespoke design that ties in with your home’s aesthetic.

Cost: Around $3500/sqm.

Sleepout studio

Some areas of building are exempt from the consent process; this may include a sleepout or ‘accessory building’. As described by Auckland Council, it does not include a kitchen or food preparation space but may feature sanitary facilities or a drinking water supply.

Such a building must adhere to the Auckland Unitary Plan and might need a resource and/or building consent depending on the structure.

A separate dwelling (exempt from the consent process) can have one or more bedrooms, but it must comply with the Building Code and meet the requirements of the Healthy Homes Standards. “It must also be part of a bigger property with associated facilities,” says Dave. “It can’t be rented as an independent dwelling as it will not have bathroom or kitchen facilities.”

“With a separate dwelling being a habitable space, the Building Code requires a smoke alarm, fresh air ventilation, natural lighting, adequate room height and thermal insulation. It must also have ready access to an existing dwelling for sanitation.”

Homeowners should seek support from a building professional, such as a chartered professional engineer or a licensed building practitioner, for more information.

Prefab dwelling

A prefabricated home is manufactured off-site in advance, then transported and assembled to your property. Some range from 16sqm for around $25,000 to passive contemporary homes with unique heating and cooling qualities. One example being Coolhouse’s Mini Home, which was derived from a client who wanted to extend their home without touching it. The Mini Home covers a 28sqm floor area and up to 30sqm of deck.

Cost: Around $6500/sqm.

Kitset dwelling

If you’d like to have a hand in the building, consider a kitset home. How it works is a company provides the design, consent and materials while you take care of the build. Kit Homes create kitsets from 62sqm, starting around $74,000. Delivery to areas with high wind and coastal locations may require additional costs. “You go through the concept design with us,” says Matt Lonsdale, co-director of Kit Homes. “We
do the working drawings, preparing them for council sign-off, while the client organises builders and sub-contractors. We have a range of standard kitset designs clients can choose from, so it’s a quick and easy process. A kitset home means people can have some control; some people are quite practical and want to be involved with the build but need people with experience to assist with the process.”
Once your groundwork is done, you can enjoy the fun part – making it look stylish. Finishing touches such as landscaping will create a cohesive, attractive look. Plantings and paint can go a long way in making it look appealing, providing a practical asset and a beautiful one too. Check out the helpful online resource Can I Build It.

Words by: Catherine Steel

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