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Cost of Building a Granny Flat in Sydney in 2021

In 2018, the state of New South Wales built over 6,000 granny flats. Granny flats are small, compact, versatile and have taken Australia by storm as a housing solution to the country’s increasing population. 

They’re perfect for the growing teenagers and ageing parents in the household, which is why many families have begun to see them as a viable option in creating extra living space for their loved ones without them being too far away.

If that alone hasn’t swayed you towards choosing granny flats, then maybe the fact that they’re also a wise investment will. Compared to the cost of buying or building an entirely new house or unit, with granny flats, you are guaranteed to save a lot more. Considering that you can put them up for rent, they can also create an additional income stream. Granny flats are a great way to add value to your property without taking up too much space.

How much will it cost to build a granny flat?

Granny flats can cost as low as $10,000 to as high as a resounding $250,000. Still, estimating granny flat prices is no easy feat since a lot goes into what constitutes the price of your granny flat construction. To ensure your money will be spent wisely, you’ll need to take a lot more than just a simple price tag into consideration.

Here are the main factors that affect the cost of building a granny flat.

#1 - Granny flat builder

After deciding on investing in your own granny flat, another equally important decision awaits right around the corner – choosing the builder to make your granny flat vision come to life. It’s critical that you choose a reputable company to handle the project – one with valid credentials and excels in residential granny flat design and construction, specifically within Sydney.

Be wary of deceptive companies trying to lure you in with low starting prices. More often than not, they end up being more expensive than companies that are upfront with their costs. Especially if you’re a beginner, you should be very thorough when selecting a contractor to get the best quality for the best price. Bellcast Granny Flats offer personalised plans for your specific needs and provide honest cost estimates.

#2 - Site costs

Additional jobs imposed by the site, such as pre-construction works and obstruction removal, factor in the total cost of building a granny flat. Be sure to clarify these with your builder prior to construction to prepare your finances.

#3 - Flat size, design, and complexity

Of course, the size of the structure is a factor in how much you’ll pay for the project. Most granny flat companies will present the same three options for their clients: one-bedroom granny flat, two-bedroom granny flats, and three-bedroom granny flats.

One-bedroom granny flats are the smallest and of course the most affordable granny flats that you can add to your property. Depending on your needs, this is usually enough for most Australian households. However, most investors in Sydney tend to go for two-bedroom granny flats. Two-bedroom granny flats have recently grown popular because of their versatility to all kinds of lifestyles. They also provide a longer-term strategy perfect for families looking to settle and investors looking for great returns.

If you have the yard space to work with and are located close to universities and tourist spots, you can even push it further by building a three-bedroom granny flat. They provide the experiences of a regular house for a fraction of the cost and make a great rental asset.

You can choose between preset designs and custom-made designs should you want adjustments to your flat to cater to your exact requirements and preferences. The latter will cost a lot more but will help you in building a granny flat in Sydney with customised designs that suit the needs of your lifestyle.

Below are the average costs of granny flats with preset designs.

Granny Flat Size

Price Range


$50,000 - $120,000


$100,000 - $200,000


$150,000 - $250,000

    The price would of course depend on the exact size and the features you want to be included, so it’s best to call us at 1300 661 370 for a more accurate quote.

#4 - Foundation

Another determining factor for the cost is the foundation of your granny flat. One of the first financial decisions you’ll have to make is to choose between concrete slab or bearers and joists.

Concrete slabs are the standard and most affordable foundation, while bearers and joists floor systems are another story. If your site has sloping blocks or rocky surfaces where additional scaffolding installation is required to level the site, expect that to influence the price. In cases such as these, bearers and joints are more cost-effective than the usual concrete slabs because they eliminate the need for excavation and save you from added expenses.

#5 - Inclusions

Your chosen granny flat finishes and features will also add up to the expenses. Standard contractors will only turn over a bare structure. The edge of Bellcast Granny Flats is that we provide a wide range of inclusions that other contractors will charge as extras.

The builder you choose will impact the overall cost of your granny flat construction more than any other factor. Pick one that has your best interests at heart -  Bellcast Granny Flats

Call the best granny flat builder in Sydney now at 1300 661 370.