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How much is a House Extension?

Average Price
$3,000 per square meter

How much does a Home Extension cost on average?

Is your family outgrowing your home but not sure how much a house extension will set you back? Read our handy guide to find out how much it will cost to carry out a home extension.

What is a House Extension?

In a nutshell, a house extension is a new building or room that is added to your existing property. Home extensions come in all shapes and sizes depending on your budget and the amount of extra space you wish to add. For example, you can add a simple single-storey extension at the back of your home. This would only involve removing a partial wall or demolishing an existing wooden extension in favour of brick.

House extensions can also be far more extensive, especially if building to the side of your home would require the external walls to be demolished and rebuilt. The most expensive home extensions span more than one storey high. Though, these are likely to add the most value to your home especially if extra bedrooms or bathrooms are created. 

What is the average price of a Home Extension? 

If you’re wondering how much a house extension costs, here’s a breakdown of average prices in Australia: 

Average cost of a House Extension
Minimum cost (per square meter)$2,000
Maximum cost (per square meter) $4,000

It can take between 6 and 20 weeks to complete a home extension, and labour makes up a large portion of the costs. You may also require various planning certificates or assessments before the work can even begin, which could be as much as $200 each. 

Factors influencing the cost: 

 The cost of a house extension can vary significantly. Here are the main factors impacting the cost: 

  • Your existing property

  • The extension size

  • Single or multi-storey

Your existing property

The age and style of your property could determine which type of extension is more suitable. Although getting expert advice does come at a cost, it will ensure the potential of the property is reached. 

As there are so many ways you can go about extending your home, you need to decide what is most important. For example, is it simply a case of wanting a bigger kitchen, or would the upstairs also benefit from an extension too? 

Remember that the size of your garden will probably be reduced as a result of getting a house extension. You’ll also need to consider any access issues too, especially if you are building out to the side of the property. It’s possible to build a double-storey extension that is hollowed out at the bottom so that you don’t lose access.

The extension size

House extensions come in all shapes and sizes. Most home extensions are billed by the labour per square meter, so size will be the biggest factor to impact the overall cost. If you have a lot of land at the side or rear of your property, then you have room for a larger extension. But with the added floor space comes an increased cost.

Single or multi-storey


The most common and cheapest form of a home extension is a single-storey one. As the name suggests, it will only be on the ground level of the property. A single-storey extension can be used to add more space to any lower floor room in your house. While a single-storey extension is most commonly used to increase the size of your kitchen or dining room, it can also create additional bedrooms if you live in a bungalow. 


Double-storey extensions involve both the ground and the first floor. At the top, you can either choose to add a flat roof or extend your current roof space to blend with the look of your property better. Adding a roof will be more expensive, but does give the option for a loft conversion in the future. 


Another option is a multi-storey extension. This will give you additional space on the ground floor, first floor, and the top floor of your home. Multi-storey extensions are the most expensive but will add the most value to your home, especially if additional bedrooms or bathrooms have been created in the process.  

Average cost of a Home Extension based on the type of extension
Type of extensionHighest average price (in total) Lowest average price (in total)
Single storey$35,000$8,000
Double storey$55,000$20,000
Multi-storey $100,000$40,000

If you’re on a budget, then a single-storey extension is your best bet as it’s the cheapest option. The prices fluctuate because your builder will be working in the square meters you wish to add, rather than the extension type alone. The spec of the build whether it be basic, standard, or deluxe is also going to impact the price.

Multi-storey extensions are the most expensive. However, as these will increase the living space on every level of your home this will be reflected in the value of your property. 

Does the cost of a Home Extension differ according to location? 

Here’s a breakdown of how much a contractor will charge per hour on average for a home extension based on where they live. 

Cost of a House Extension based on location
LocationBuilder average hourly rate

Builders will either work on a day rate, hourly rate, or a fixed fee. As house extensions take several weeks, labour is a huge part of the cost. On average, builders in Australia charge between $28.56 and $40 per hour. 

Other considerations 

  • Fixtures and fittings - The fixtures and fittings will also determine the costs. Luxury materials such as Velux windows or marble flooring will add more costs to the project. Likewise, your extension will need insulation and external rendering. In addition to this, you need to consider whether you’ll need to pay someone to carry out electrical and plumbing work.

  • Planning permission - Planning permission is of course the top consideration for any building work you wish to undertake. This especially is the case if you live in a listed building. There will be costs associated with surveyors and architects, especially for more ambitious projects. If you have neighbours that live nearby you’ll also need to consider their needs too. If the building work is set to be disruptive, it’s always worth talking it through with your neighbours. Remember to consider whether the building work will block light from their property or intrude on their land.

Getting a House Extension - is it worth the cost? 

Getting a house extension is ideal if you’ve outgrown your home but you’re not prepared to move. Extending your property can breathe new life into it, creating a warm and inviting space to raise your family in. 

As an example, many period properties have a small kitchen that’s not fit for dining or entertaining. A single-storey extension would greatly increase the amount of space you have for cooking. 

Likewise, if you have a small ‘box room’ bedroom, a double-storey extension would turn this into a double room. Plus, it would add more living space downstairs too. If your extension is carried out to a high standard, it will most certainly add significant value to your home.

A home extension is an excellent way to add value to your home. From new additions to the family to more usable space, they allow you to meet your space needs without having to move. 

Find local builders for your House Extension with Bark. 

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