Granny flat DIY kit or professional build: which is cheaper, easier and better overall?

Is a granny flat kit home just as good as a professional build? Is it cheaper to DIY? We explain it all here.

If you’re exploring the idea of adding a granny flat, you’ve probably realised there are two ways to build it: using a prefabricated kit that you assemble onsite or engaging a builder who’s designed it from scratch. That decision will determine the cost and overall outcome of your project.

Let’s look at all the options, starting with how each type of build works.

A prefabricated kit home: comes in pre-set sizes and is delivered to your door as a flatpack with assembly instructions. You can customise the design to add extra doors, windows, internal walls and even a deck for extra costs. All fittings, fixtures, painting, electrical and plumbing will need to be organised by you and – where necessary – carried out by a professional.

A custom-made professional build: is managed by a builder or building company that runs the project similarly to a house build. You’ll choose from pre-designed blueprints or draw up your own, with plenty of customisation flexibility. The build team will carry out the project from start to finish, ending in a move-in-ready home.

Table of Contents

Pro vs DIY: 6 comparisons

To help you decide which kind of build will work for you, we’ve highlighted 6 major factors to consider. For each point, we’ve explained the difference between a DIY Kit and a Pro Build.

1. Inclusions and exclusions.

A granny flat needs a kitchen, bathroom, flooring, plumbing, rainwater goods and connections, electrical outlets, fans, air conditioners, lighting and smoke alarms that all need to be certified by a building inspector before it can be lived in.

DIY Kit: You won’t get any of these included in your flatpack. This can be the most daunting part of a kit home; you’ll need to create your own lighting plans, design kitchens and bathrooms from a blank space, source every item including flooring, gather quotes and engage professionals to install each element – all in the right order.

Pro Build: Usually, a build team will include a designer who can help you plan your home inside-out including wall colours, flooring and the best lighting layout. The team will take care of all installations and make sure it’s 100% compliant.

2. Project time.

The time it takes to complete your granny flat is determined by the size, weather and who builds it.

DIY Kit: If a kit granny flat says it’s a 1 to 3 day build, it’s referring to erecting the internal and external walls and roof (on a base you’ve already built). After that, completing the home is on your timeline as the project manager. Research from Finder says the average granny flat build is 900 hours, which must fit around work and other commitments if you’re building it yourself.

Pro Build: A turnkey granny flat build is much like a regular house project, and can take between 12 to 16 weeks depending on the size. A good builder will manage the project and keep you up to date on the expected finish date; you won’t have to do anything except watch it take shape.


3. Budget control and price.

Building a home is a big-ticket item no matter how small or who builds it. Keeping the budget under control starts from the moment you start researching, and many DIYers are surprised by some of the hidden costs.

DIY Kit: Nearly 40% of DIY builders exceed their budget due to unforeseen expenses, according to a report by Archicentre Australia. In fact, the HIA says DIY granny flat projects can cost homeowners up to $20,000 more than if they’d had the home built by professionals.

Pro Build: Working with a building company means you’ll be quoted a price from the beginning, and you can choose fixtures and fittings to suit your budget. Your builder will do everything possible to stay within budget (some may even offer fixed prices). A projected cost is a huge relief for a homeowner.

4. Resale value.

Granny flats increase your overall property value, but how much depends on the quality of the build.

DIY Kit: If it’s clear the granny flat wasn’t built correctly or doesn’t have the right certification, it could negatively impact your resale value. Potential buyers may see it as a liability or recognise the extra expense needed to correct it.

Pro Build: Research from says professionally built granny flats have a higher rental yield compared to DIY homes, and attract better quality tenants. You’ll also save on repairs and maintenance, and have a home that can last decades.

5. Turnkey finish.

It’s easy to forget that there’s more to a granny flat than the building. It may need decking, fencing, gardens and surrounds, grass and paths as well as letterboxes and driveways.

DIY Kit: You’ll need to design and complete every task yourself, either with your own hands or by outsourcing to contractors.

Pro Build: A good builder will include many of these extras so it’s ready on handover with nothing else to complete.

6. Extras and warranties.

Building a granny flat is an enormous project to undertake. It requires knowledge of council requirements, permits, awareness of the right location to build, and final approval of the building.

DIY Kit: You’ll need to do all the research yourself, including contacting the local council about any limitations on building granny flats in your neighbourhood and information on easements or sewerage on your property, and run a Bushfire Attack Level assessment. You also won’t get a builder’s warranty, which would cover you for any issues for a year after completion.

Pro Build: If you choose a local builder, they’ll be familiar with council regulations as well as every box that needs to be ticked to build a granny flat from start to finish. They’ll take care of every detail, including insurance and safety requirements. At completion, you’ll be handed a turnkey-ready home with full approval and a builder’s warranty. 

The final valuation

If you have some building experience, you may be able to undertake a DIY granny flat kit home with some level of ease. However, for a regular Australian, a kit home can end up being an intensely stressful experience that drags on for months and often blows out the budget.

We’ve attended many homes with a half-constructed granny flat and desperate homeowners asking for help to complete it. It’s not an easy task, and we haven’t seen any evidence that kit homes are cheaper or easier.

If you’re thinking about a granny flat, make sure you get a quote from a professional builder – you’ll likely find it’s far cheaper than you expect and you won’t need to lift a finger while it’s being constructed.

Our team at DC House Granny Flats is incredibly friendly and ready to help you, right from the initial assessment and quote all the way through to design and build. There is no cost to request a free consultation. We look forward to hearing from you!

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